Anal. Chem. 1985,57,94R-114R (167) Ohls, K.; Rlemer. G. Fresenius' Z . Anal. Chem. 1984, 317, 774-9; C A , 100:220832w. (168) Ohls, K.; Rlemer, G. Fresenlus' 2.Anal. Chem. 1984, 317. 780-1; C A : 100:220833x. (169) 'Subrahmanlam, P.; Rao, 8. V. Trace Anal. Techno/. Dev. 1983, Spec. Contrib Pap. Int . Symp ., fst, Meeting Date 1981, 383-7. (170) Horl, M.; Hlrako, M.; Ishil, K.; Kobayashl, Y. BunseklKagaku 1984, 33, 203-9. (171) Campbell, A. D.; Graham, P. 8. N . Z . J . Sci. 1983, 2 6 , 433-5. (172) Braun, H.; Metzger, M. Fresenlus' Z . Anal. Chem. 1984, 318, 321-6; C A ; 101:182937v. (173) Brumleve, T. R. Anal. Chim. Acta 1983, 155, 79-87. (174) Ye, H.; He, Y. Talanta 1984, 3 1 , 638-41. (175) Cassinelll, C. Rlv. Mlneral. Ital. 1983, 3 , 85-90; C A , 100:131476t. (176) Terashima, S. Anal. Chlm. Acta 1979, 708, 113-18. (177) Baird, A. K. J. Geophys. Res., 8 1984, 8 9 , 2491-6. (178) Alnes, R. D.; Rossman, G. R. J . Geophys. Res., 8 1984, 8 9 , 4059-7 1. (179) Paullk, J.; Paulik, F.; Arnold, M. J . Therm. Anal. 1982, 2 5 , 327-40. (180) Huggins, F. E.; Huffman, G. P. J. Appl. Phys. 1984, 55, 1404-9. (181) Zolotov, Yu. A. Net., Aim Methods Microchem., Proc. Int. Microchem. Symp., Bth, Meeting Date 1980, 1981; Hanns, M.; Grasserbauer, M.; Betcher, R.; Eds, Springer Verlag, Austria, 1981, 231-56. (182) Murthy, R. S. S.; Holzbecher, J.; Ryan, D. E. Rev. Anal. Chem. 1982, 6, 113-50. (183) Wannlnen, E. Euroanal. 4, Rev. Anal. Chem.. 4th, Meeting Date 7981, 1982, 157-71. (184) Kosta, L. Talanta 1982, 2 9 , 985-92. (185) Burke, R. W.; Mavrodineanu, R. N8S Special Publication, No. 260-81, 1983, 126 pp. (186) Museller, J.; Staats, G. Fresenius' 2. Anal. Chem. 1984, 318, 317-20. (187) Mitra, N. K.; Das Poddar, P. K.; Dastldar, R. G. Indian Ceram. 1983, 2 6 , 83-4. (188) IUPAC Analytical Chemlstry Division, Pure Appl. Chem., 1984, 56 479-89. (189) Foner, H. A. Anal. Chem. 1984, 56,856-9.
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(190) Haas, E. W.; Beuerle, M.; Hofmann, R. J . Radioanal. Nucl. Chem. 1984, 8 2 , 7-32; C A , 100:220671t. (191) Hung, C. F.; Chen, P. Y.; Weng, L. Y.; Huang, H. L.; Yang, M. H. Talanta 1984, 3 1 , 259-63. (192) Massart, D. L.; Esbensen, K. H.; Kaufman, L. Anal. Chem. 1982. 5 4 , 911-17. (193) Grornet, L. P.; Dymek, R. F.; Haskln, L. A.; Korotev, R. L. Geochim. Cosmochim. Acta 1984, 48, 2469-2482. (194) Pilllnger, C. T. Geochim. Cosmochim. Acta 1984, 48, 2739-2766. (195) Dubessy, J.; Galsler, D.; Kosztolanyl, C.; Vernet, M. Geochlm. Cosmochlm. Acta 1983, 47, 1-10. (196) Goodman, B. A.; Green, H. L.; McPhail, D. B. Geochim. Gosmochim. Acta 1984, 48, 2143-2150. (197) Dlllard, J. G.; Crowther, D. L.; Calvert, S. E. Geochim. Cosmochim. Acta 1984, 4 8 , 1565-1589. (198) Loss, R. D.; Rosman. K. J. R.; De Laeter, J. R. Geochim. Cosmochim. Acta 1984, 48, 1677-1681. (199) Roddlck, J. C. Geochim. Cosmochim. Acta 1983, 47, 887-898. (200) Koch, H. Isotopenpraxis 1984, 2 0 , 41-7. (201) Mukherjee, B. K. J . Mines, Met. Fuels 1983, 3 1 , 313-15. (202) Klesl, W. CRC Crlt. Rev. Anal. Chem. 1984, 15, 119-61. (203) Toelg, G. Pure Appl. Chem. 1983, 5 5 , 1989-2006. (204) Steger, H. F. CANMET Rep. 1983, 83-3€, 35 pp. (205) Govlndaraju, K.; Mevelle, G. Spectrochim. Acta, Part 8 1983, 386, 1447-56. (206) Delfanti, R.; Di Casa, M.; Gallorini, M.; Orvini, E. Mlkrochim. Acta 1984, 1 , 239-50. (207) Xilei, L.; De Corte, F.; Moens, L.; Simonits, A,; Hoste, J. J. Radioanal. Nucl. Chem. 1984, 8 1 , 333-43. (208) Tu, S. D.; Hanf, W.; Lleser, K. H. J . Radioanal. Nuci. Chem. 1984, 8 3 , 407-12. (209) Cortes, E. J . Radioanal. Nucl. Chem. 1984, 8 4 , 157-64. (210) Inn, K. G. W.; Llggett, W. S.; Hutchison, J. M. R. Nucl. Instrum. Methods Phys. Res., Sect. A 1984, 223, 443-50. (211) Hanson, A. L.; Kraner, H. W.; Shroy, R. E.; Jones, K. W. Nucl. Instrum. Methods Phys. Res., Sect. 6 1984, 232, 401-3. (212) Staats, G. Fresenius' 2.Anal. Chem. 1984, 317, 761-4.
Ferrous Analysis W.A. Straub* and J. K. Hurwitz US.Steel Corporation, Technical Center, Monroeville, Pennsylvania This review is produced from a search of the literature as performed with the DIALOG capabilities of Chemical Abstracts Service. The literature covered in this review spans the period from November 1982 to October 1984 and is the sixth review in the series of reviews compiled by us. Noteworthy in this 2 year span is the significant increase in publications from the People's Republic of China as well as what appears to be an increased emphasis on the determination of gases in ferrous alloys in the industry as a whole.
ALKALI METALS The determination of alkali metals in the steel industry relates to the characterization of ores, enamel coatings on steels, slags, and coal. To achieve adequate sensitivity for sodium and potassium (474) and rubidium (209), these elements were preconcentrated by anion exchange or by liquid-liquid extraction and the analysis completed by atomic absorption spectrometry or inductively coupled plasma spectrometry. Atomic absorption spectrometry was also applied to the determination of Na and K in coals, slags, and ores without preconcentration by adding measured amounts of lanthanum and cesium to eliminate chemical and ionization interference (477). To study the corrosion rate of enamels in hydrochloric acid, the corrosate was assayed for its sodium and potassium content by dc arc optical emission spectrometry (409), while a quartz optical fiber was used to convey light from the analytical gap to the monochromator of a vacuum optical emission spectrometer in order to extend the spectral range for the determination of Na and K in ores (337). Neutron activation analysis has also been used for the measurement of Na in ores (148).
ALUMINUM Included in the reagents that have reportedly been used for the spectrophotometric determination of A1 in steels are 94 R
15146
salicyloylhydrazones of pyridine-2-aldehyde and pyridoxal (129), Chromazol KS (484), and Chromazurol S in the presence of dodecyldimethylammonium acetate (500). Aluminum was also complexed with Chromazurol S after fusing slag samples with a sodium carbonate-tetraborate mixture (601). In another procedure for the determination of A1 in iron ores, the A1 was separated and concentrated by ion exchange before the colorimetric finish with 8-hydroxyquinoline (475). The addition of butanol to a dissolved steel sample immediately before precipitation of the interfering elements by caustic has allowed the colorimetric determination of A1 with aluminon to be completed without vanadium interference (325). A recent Chinese study has established the conditions for the sensitization by various surfactants of the fluorometricreaction of Al with 8-hydroxyquinoline-5-sulfonicacid (81). A method for the determination of A1 in alloy steel was given. A hydrochloric acid dissolution step was employed before the direct atomic absorption spectrometric determination of A1 in steels in a nitrous oxide-acetylene flame (159), while a liquid-liquid extraction (209) or an ion-exchange separation (474)was used to treat a similar acid dissolution of iron ores prior to the atomic absorption determination of the Al. For the rapid determination of soluble A1 in continuously cast steel, an apparatus has been devised for electrolytically sampling the steel and finishing the analysis by atomic absorption spectrometry (323). Total time of analysis is about 125 s.
ANTIMONY This element has been determined spectrophotometrically in steel and cast iron as an ion-association complex with Crystal Violet following extraction (431), and in steels with several of a family of Rhodamine dyes (Rhodamine B, Bu ester of Rhodamine B, and Rhodamine 6G) (298). Pulse-nebulization has been used for the rapid analysis of trace antimony in steels by atomic absorption by allowing the
OOO3-27OO1851O357-94R$O6.5OlO 0 1985 Amerlcan Chemical Society
FERROUS ANALYSIS
was formed during sample decomposition and subsequently transferred to the plasma by argon (277). As the result of a study of several spectral methods for the analysis of trace arsenic in steel, it was concluded that XRF techniques were preferred (143). In a renew of sample preparation and concentration procedures, the determination of arsenic in a variety of steels, alloys, cast iron, and ferroalloys has been discussed (311),primarily with regard to atomic absorption and spectrophotometric finishes.
BARIUM Trace elements, including Ba, in several NBS Standard
!
Reference ferrous alloys and steels were determined by flame emission spectrometry after acid dissolution (443).while arc excitation was used to study the corrosion rate of enameled steels in various acids by measuring the buildup of barium in the corrosate (409). For the determination of barium in bearing steels, iron had to be removed by extraction before the Ba could be measured by electrothermal atomizationatomic absorption spectrometry (626,627).
BISMUTH
aspiration of more concentrated solutions (6W. A study has been produced that optimizes the conditions for the use of various acids and their effect on the atomic absorption d e termination of Sb in steel Nitric acid was recommended (141). Extractive separation of S b with TOPOJi-BuCOMe was combined with pulsed introduction into an m c e t y l e n e flame for the determination of PPM in steels (204). while extraction with ammonium pyrrolidinel-carbodithioateinto chloroform and subsequent hydride generation from this matrix for a final atomic absorption determination has ala0 been reported (25). A preliminary methylene blue extraction followed by wet oxidation of the extract and ac inverse voltammetry of the final product has been used for the determination of traces of Sb in ferrdoys, iron, and steels (426). An extractiowback extraction technique has also been coupled with differential-pulse polarography for the analysis of steels used in nuclear a plications (291). In a test of three spectrochemical m e t h d s for the determination of microimpurities including antimony in steels, it was concluded that the X-ray fluorescence method was the most promising (143)
ARSENIC Nitric acid was recommended in the preparation of steel samples for the atomic absorption determination of As (141). after a study of several acids for this purpose. Spectroph+ tometric methods for the determination of trace As in steels have been described in which molyhdoarsenate complexes with crystal violet (623) and ethyl violet (34.5)have been used for steel analysis. In the latter case,15 standards were evaluated with the method and the results were in good agreement with certified values. Two anodic stripping voltammetric methods utilizing codeposited gold films on glassy carbon (292) or graphite electrodes (343) have been reportedly used for the measurement of trace to low levels of As in steels. An extraction-fast-scan differential-pulse polarographic determination a t a mercury drop electrode has been applied to the determination of As in nuclear alloy steels (291) with a recovery of 1W%. An argon-swe t optical path was used to enable the vacuum-ultraviolet &termination of As in iron and steel by inductively coupled plasma emission spectroscopy (160). In another variation of ICP technology, volatile arsenic chloride
Amines such as tri-n-octylamine, triisooetylamine. or Aliquat 336 have been used to extract bismuth from steels for a subsequent spectrophotometric determination with thiourea (497). Another sensitive spectrophotometric method for the determination of bismuth in iron and steel uses the ternary complex with iodide and Rhodamine B (296). A variety of atomic absorption methods have been descrited for the determination of Bi as follows: in single steel particles in a graphite cup cuvette (with a primary and secondary atomization effect b e i observed) (534);in high- and low-alloy steels with an autosamplergraphite cup atomizer combination (302);by hydride generation from steel samples (570);after extraction from dissolved steel samples with TOP0 and pulsed introduction of the extract into an airacetylene flame (204); a pulsed nebulization of a dissolved steel sample directly in the flame (624);and a procedure that involved a physical separation of the trace elements, including bismuth, as diethyl dithiophosphate complexes on a C-coated filter, with subsequent dissolution of the filter and analysis of the solution by atomic absorption spectrometry (36). X-ray fluorescence spectrochemical methods were also recommended for the determination of traces of Bi in construction steels (143).
BOOKS AND REVIEWS During the ast 2 years, 69 books and reviews have a p peared, a sizebe increase over the number appearing in previous %year periods reviewed by us,and dexribe research and other activities in carbon and low-alloy steels (14,15,16,
20,48,49,60,102,119,I22,125,126,156,169,170,176,187, 189,198,199,201,245,250,273,317,320,329,342,356,357, 365,444,454,476,482,502,505,522,560,608,612), pig iron and cast iron (102.156,164.198,245,365,502),high alloy and stainlesasteels (65,100,117,122,152,157,164,338,365,483), slags (15,365), ores (5, 10, 15, 156, 198, 506, 539). and ferroalloys (198,539). Spectral Methods. Several specific reviewswere published on the application of emission and X-ray spectrometry (16, 100,103,117,138,170,187,266,300,329,342,367,414.454, 504,506,539,541,591,€Ci?, 612),atomic absorption (175,268, 454),and masa spectrometry (49,245). Other spectral methods reviewed were electron microprobe (31, 152) and Auger 8 ctroscopy (65,170,176,243,338).Several of these reviews escnbed surface analysis techniques (25,31,60,117,122,125, 170,243,245, 338,444,482,560).
8“.
Gases in Metals. Reviews covering advancements in the determination of oxygen, hydrogen, and nitrogen (20,55,119. 126,199,201,262,317,320,465,476)have been published. Oxygen probes using electrochemical methods are frequently described (119,199,262,465) for this determination in liquid steel. Other Reviews. With the widespread use of computers with analytical instruments, several reviews of computer hardware and software (31,48,214,413,608)have appeared in the literature. One review covered the integration of titrimetric methods with emission and X-ray spectrometry for the analysis of structural materials (103). Another paper described methods for the separation and determination of ANALYTICAL CKMISTRY. VOL. 57, NO. 5. APRIL 1985 05R
FERROUS ANALYSIS
sulfide inclusions in steel (562).
BORON Several methods have been described for the determination of boron in steel and alloys in which iron interferences are minimized by precipitation of the iron with caustic prior to a spectrophotometric finish with Azomethine H (537,538). Quinalizarin Complexion has been proven fit for the spectrophotometric determination of B in 94% sulfuric acid solution (232). Extraction of BF4- and measurement of its methylene blue ion association complex has been applied to niobium-alloyed steels (264) and to maleable cast iron (309). Curcumin continues to be exploited for the spectrophotometric determination of boron following extraction from steels (24), after fusion of some refractories and slags (45),and in steels in which the curcumin method gave results identical to a potentiometric determination in the range 2-200 ppm B (572). A comprehensive study has been published detailing the determination of effective boron by measurements of total and insoluble boron by using 1,l’-dianthrimide as the spectrophotometric reagent (285). Acid-insoluble,Br-insoluble, and iodine-insoluble fractions were used in the study. A titrimetric procedure has been described for the analysis of ferroboron in which a column chromatographic separation is used to remove iron before titration of the boric acid (433). For >0.001% of boron in low-alloys steels, a preliminary electrolysis to remove iron allowed a potentiometric acid-base titration in the presence of mannitol to be performed (146). B in steels at the 1ppb to 1ppm level has been determined by a reversed-phase HPLC separation and detection of an ion pair of B, chromotropic and Bu4NBr (344). Two methods for the determination of B in steels using ICP-AES either directly on a dissolved sample or on a alkaline-treated fraction have been described (174). ICP excitation has also been coupled with either a separation of boron from steels by distillation as an ester or by a liquid-liquid extraction prior to the final analysis step (334). Another direct ICP method for use at B levels >0.6 ppm in steels involves simple dilute acid dissolution (H2S04)and carbonate fusion to prepare the sample for excitation (104). Soluble, insoluble, and total B in steels have been determined by ICP excitation of solutions obtained after strong acid, iodine-methanol, dilute acid, or electrolytic dissolution of selected samples (321). Two papers have appeared detailing the use of glow-discharge emission spectroscopy for the measurement of the distribution of various elements including boron in the boride layer on steel (130,131). A solution spectrometric determination of boron a t a stabilized dc arc was aided by the prior removal of iron by cation exchange separation (89). An emission spectrochemical apparatus e uipped with a pulse height distribution analyzer was claime to enable the rapid determination of total, acid soluble and insoluble B by the effect of each type of boron on the intensity of emission (195). Finally, after separation of iron from dissolved steel samples by extraction chromatography, boron has been determined in the eluate by flame photometry in an air-acetylene flame (544).
2
of cadmium in high- and low-alloy steels by atomic absorption spectrometry (302). In another paper, a universal flame atomic absorption spectrometric method is described and has been applied to a diversity of samples including ores and steels (477). Trace quantities of Cd have been separated from steels by TOP0 extraction and subsequently determined by pulsed introduction of the extract into an air-acetylene flame in one method (203) and by absor tion of the complex formed between Cd and ammonium gethyldithiophos hate on an activated C-coated filter, followed by atomic agsorption spectrometric measurement of the dissolved filter for its Cd content (36). Optimum conditions have recently been described for the direct emission spectrographic determination of Cd in steels with a detection limit of 4 ppm (242).
CARBON Carbon was determined with a spark-source optical emission spectrometer in pig iron (223)and steel (331)and in steel by a glow discharge optical emission spectrometer (226,350). A high energy prespark was used to homogenize the steel sample surface (501) prior to determining carbon by a low-energy spark. Two papers describe the use of mobile optical emission spectrometers for steel sorting. In one, the radiation is conducted by a fiber-optic cable to the spectrometer (144)and in the other a flowing argon stream carries the aerosol produced by a dc arc discharge to a second arc discharge in front of the entrance slit of the spectrometer (546). X-ray spectrometric methods have been described for the determination of C in steel with a microprobe (168,340),in austenitic stainless steels with up to 0.3% C (332),but with poor precision, and in cast iron (412). In the last reference, Compton scattering of X-rays emitted with a Cr target X-ray tube produced sufficient intensities for the determination of carbon. Surface carbon has been measured by combustion in a low-temperature oxygen plasma and completed by infrared spectrometry (286) or combusted in oxygen with tungsten oxide-tin pellets as combustion aids and the analysis completed by infrared spectrometry,coulometry,or conductometry (261). For the determination of bulk carbon, popular methods involve combustion in oxygen and completing the analysis by gas chromatography (32), infrared spectrometry (18), or coulometric titration (609). Hydrogen hot extraction techniques have been described for the conversion of carbon to the hydride and measurement of the gas with a mass spectrometer (385,402). Neutron activation methods are available for carbon determinations in steel (33) and coke (95). An electrochemical cell that contains oxides of zirconium and yttrium has been developed for the direct determination of carbon in the furnace during the melting of stainless steel (257). A recent Czechslovakian patent describes a means for sampling gases evolved from liquid steel with a porous melt resistant probe with subsequent measurement of the CO and C02 concentrations evolved and calculation of the carbon content of the melt from these data (429).
CALCIUM
CHROMIUM
Application of atomic absorption spectrometry to the determination of calcium is illustrated by the analysis of oxide inclusions after electrolytic separation and fusion with POtassium hydroxide (366)of ores, slags, coals, and steels (477), and iron ores after separation by anion exchange (474). Effects of nonhomogeniety and particle size on calcium results in the analysis of iron ores are discussed (251) and recommendations for sample preparation by grinding are presented. Calcium was determined in slags by X-ray spectrometry after fusion of the sample with lithium tetraborate. Atomic emission spectroscopy was used for this determination in steel at trace levels (443) after dissolution in a combination of mineral acids while dc arc emission spectroscopy was employed to determine calcium eroded from enameled surfaces of steel by hydrochloric acid (409).
The determination of chromium by atomic absorption spectrometry has several interferences, particularly iron. These interferences are minimized in the analysis of ores by liquid-liquid extraction or by ion exchange to remove the iron and concentrate the chromium (209,474)or by the addition of La or Cs to the sample solution (477) before completing the determination in the analysis of stainless steel. This problem is minimized by matrix matching of standards with samples (263,310).Flow injection methods were used for this determination in steels (566,567). Chromium has also been determined in iron-chromium electroplated surfaces (282). Atomic absorption spectrometry has been used to monitor the electroplated thickness being deposited by measurin the chromium vapor concentration in the plating chamber b69). Several papers were published describing the spectrophotometric determination of chromium in steel, stainless steel, and ores. The complexing agents used for color development include several arsenazo compounds (127,530,531,598,619), tropolone (461),ethylenediamine-NJV’-dipropiqnicacid (641, diphenylcarbazide (38),sodium 2-bromo-4,5-d1hydroxyazobenzene-4’-sulfonate (577), and cyclohexane-1,3-dione bisthiosemicarbazone monohydrochloride (450). A dual beam
CADMIUM The trace determination of cadmium in iron ores has been accomplished spectrophotometrically with a Cd complex of 2-(3,5-dibromo-2-pyridylazo)-5-dimethylamine in the prescence of Tween-80 (132). A modified autosampler has been coupled with an electrothermal atomizer for the direct determination 96R
ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
FERROUS ANALYSIS
monochromator was re ortedly developed specially for monitoring chromium in e ectroplatin wastewater (91). Volumetric methods involving t e titration with standard ferrous solutions were developed for this determination in steel and cast irons (283),steel (620),and other steel alloys (518). Trace concentrations of Cr in ores can be determined polarographically using a sodium nitrite-o-phenanthroline electrolyte solution buffered with ammonia (599). Hollow cathode (56)and glow discharge sources (9,56,350, 576) were employed for the emission spectrometric determination of Cr in steels and stainless steels. The determination limits approached those obtained with a spark source. Trace concentrations were determined with an inductively coupled plasma after separation and concentration of chromium by liquid-liquid extraction (209). Cr was also measured in steel with a spark source optical emission spectrometer (182) and through a chromized layer on boiler pipe (280). Energy-dispersive X-ray spectrometry was used to determine chromium in steel and stainless steel (478) and small irregular steel fragments (479). The use of a computerized X-ray spectrometer (106)saved 80% of the time normally used to accomplish the same determination by manual X-ray fluorescence equipment and an atomic absorption spectrometer previously used. Corrosion-resistant coatings on steel were analyzed for Cr after calibration standards were analyzed by atomic absorption spectrometry and ICP-OES (155). Two papers appeared describing PIXE and Rutherford backscattering methods for the determination of this element (470, 554). Photon-induced prompt photon spectrometry (136),gas chromatography (336),and solids mass spectrometry (463) have all been used to determine Cr in steel.
p
i
COBALT The ion-pair complex formed by cobalt with 1-(2-pyridylmethylene)-2-(2-pyridyl)hydrazine and dimethoxyanthracenesulfonate has been used in extractions for both a spectrophotometric or a spectrofluorometric measurement of Co in steels (53), as has ammonium tetrathiocyanatocobaltate(I1) propylene carbonate (54). The role of the propylene carbonate in this determination was elucidated in an earlier study (551). Other reagent systems develo ed for the extraction-spectrophotometric determination of o in steels include 2’-(8-quinolinylazo)-5’-diethylaminophenol(149), thiocyanate-hexamethyl hosphoramide (339), 2,2’-dipyridyl-2-benzothiazolylhy&uone, used either directly or with an extraction step (503),and 7,14-dimethyl-5,7,12,14-tetraethyl-1,4,8,1l-tetraazacyclotetradeca-4,1l-diene with caproic acid (524). Direct spectrophotometric determinations were reported with the reagents 2-(mercapt0acetamide)benzenesulfonate (322), with the violet complex formed between Co(II1) and EDTA after removal of Fe by precipitation (445), with a coprecipitation of morpholine-4-carbodithioate and naphthalene that is measured after redissolving in CHC13 (483),and with 2-(2-thiazolylazo)-4-methyl-5-(sulfomethylamine)benzoic acid after removal of Fe and Mn (575). Co(I1) at the trace level in the presence of 2000-fold amounts of Ni and Mn and a 1000-fold amount of Fe can be determined by ac polarography in buffered 2,2’-dipyridyl electrolyte (408) and by differential pulse polarography by measuring the catalytic reduction wave of the dimethylglyoxime complex (588). Following acid dissolution, evaporation and mixing of the residue with carbon, trace Co in steels and pig iron can be determined by emission spectroscopy with arc excitation (7). Cast irons and steel samples were also analyzed directly by dc arc excitation as well (316). Several methods of background correction have been investigated and applied to the ICP-AES determination of microamounts Co in iron and steel (105). Low-wattage glow discharge emission spectrometry was studied for the analysis of several iron-based alloys, including Fe-Co with particular emphasis on the effect of sputtering parameters on the emission intensities (576). Proton-induced prompt photon spectrometry has been investigated for the determination of >0.10% Co in steels and was found to yield a relative precision of 2.3% at this level (136).
8
COPPER Following extraction, Cu has been determined spectrophotometrically in steels and ores as a Xylenol Orange-cetylpyridinium complex ( I l l ) , as a complex with phenanthraquinone monothiosemicarbazone (237),as ion pairs with
Bromocresol Green, Thymol Blue, or picrate and 1,1,4,8tetrathiacyclotetradecane (467), with l-(Z-pyridylazo)-Znaphthol (424),as complexes of some unsaturated macrocyclic tetraamines with several carboxylic acids (524), as a diethyldithiocarbamatecomplex after removal of interfering iron by precipitation (399),and directly with several water-soluble azo dyes (425). Fe ores have been analyzed using the deep blue color of the Cu-EDTA complex at higher concentratons and the diethyl dithiocarbamate complex at lower concentrations (441). At about pH 5,Cu and diphenylcarbazoneform an insoluble complex in the presence of tartaric acid that can be filtered, redissolved, and subsequently titrated with EDTA. This procedure has been applied to steels (578). Cu in steel samples has been determined directly by electrothermal Zeeman atomic absorption spectrometry (23),by atomic absorption at relatively high levels (50%) in alloy mixtures after several dilutions (330),by a universal flame atomic absorption method in diverse materials (477),in iron and steel by a combination of complexation and filtration through an activated C-coated filter, with subsequent workup of the dissolved fiiter by atomic absorption spectrometry (36)and in iron ores by a procedure that requires prior removal of interfering iron by liquid-liquid extraction before either an atomic absorption or ICP finish (209). A comparative study has been made of the use of glow discharge and hollow cathode excitation for alloy steel analysis. Optimum conditions have been determined for the determination of a number of elements including Cu (56),while another study of several reference steel standards by three spectrochemical techniques concluded that the X-ray fluorescence method was preferred with respect to reproducibility and range of concentration (143). The effects of some basic conditions such as sample surface pretreatment and selection of standard reference materials were reportedly evaluated for the determination of Cu in cast iron by XRF (386).
EMISSION SPECTROMETRY A recent review of developments in the ferrous metals industry focuses on the use of pulse height distribution analysis in spark source optical emission spectrometry, glow discharge spectrometry, and inductively coupled plasma spectrometry (185). The same topics are covered in another comparitive review published by a German group (247). Analytical accuracy was the subject in another paper that discussed the suitability of direct reading spectrometers and means for achieving consistent and accurate performances from them (238). Burr chips were used for analysis with an analytical system consisting of an ARL 36000 alloy sorter, a LECO 112 C carbon analyzer, and a portable X-ray analyzer for on-site checking of plant construction materials (590). For control of refining and casting operations, a spectrometer equipped with an electrical discharge source, an optical fiber transmission system, and a spectrometer has been patented (523, while fully automatic optical emission spectrometer has been developed for use with a continuous steel making process and provides analyses in 50 (124). The Polyvac E 1000 has been evaluated and applied to the analysis of cast iron, pig iron, steel, and stainless steel for 18 elements (394, 395). The preparations of samples, calibration standards, and recalibration standards are discussed. For the determination of trace elements in super alloys, high-purity metals, and oxides, an automatically controlled hollow-cathode li ht source has been developed and operated successfully (2157. In another development of this type, a demountable hollow-cathode has been designed in which a tubular sample forms the cathode and can be sputtered from both ends (35). This design yields very low detection limits. Similarly, the effects of the superposition of a microwave field upon a hollow-cathode discharge were investigated for use in the spectral analysis of steel. It too gave lower background levels that in turn permitted lower detection limits for several metals (63). Depth profiles obtained by emission spectrometry with a glow discharge lamp have been achieved with high reproducibility by controlling variables associated with the power supply, sample temperature, and the influence of air (246). A modified glow discharge procedure, in which the abnormal fluctuations in the first stage of the discharge are excluded ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
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has provided a means of accurate depth profiling of iron and steel surfaces (398). Glow discharge s ectroscopy has been oxide films on Crapplied to the analysis of thin (25-65 Mo-low-alloy steels (46)and for the bulk analysis of low alloy steels (86,87). Discharge parameters such as current, voltage, power, and gas pressure and sample conditions such as microstructure and hardness, particularly for the analysis of high-alloy tool steels, are discussed (87). Successive layers of steel surfaces have been anodically dissolved and the solution subjected to ICP spectrometric analysis. Detection limits for most elements were in the range of 0.01% (154). It is claimed in a recent paper that a computer-controlled Multiquant program in concert with an ICP source can be used to automatically determine 29 frequently required elements in unknown samples with errors no greater than 25%. Three elements were used in the standardization procedure (213). A totally automated high-precision ICP spectrometer has been developed in which either the absolute intensity or relative intensity quantification method is chosen depending on the concentration range of the element of interest (376).It has been demonstrated effectively for the high precision determination of Si in steels. A paper and two patents describe the details of design, operation, and applicability of a combined laser ablation-ICP source for bulk steel analysis (193,222)and for the determination of trace impurity elements in steel (225). Low voltage discharge was used to produce metallic vapors that were then swept by an argondriven aerosol cyclone into an ICP source for excitation and analysis (535). Low alloy steels were analyzed satisfactorily by this means by using a Quantovac spectrometer. A series of papers have described the characteristics of high-voltage spark effluents with regard to physical properties and their emission spectral properties when channeled through a microwave discharge plasma (165,166).Other studies from the same group described the use of high-power positionally stabilized sparks for emission spectrometric analysis of several ferrous alloys (586)and the statistical mapping of the surface of alloy samples by using these stable sparks to improve control of the resolution of the sampling process during emission spectral analysis (404). Another group of papers reported on the results of studies of the use of the microspark method of Sam le excitation in a steaming gas atmosphere. Included were di)scussions of the effect of the gas used, its flow and sparking rate and counter electrode material (556,558), time (557). Steels, stainless steels, and alloy steels were analyzed. A system has been described that allows the blowing of powdered samples at the rate of from 5-400 mg/min into an ac arc source for excitation. The method was demonstrated for the analysis of ferroalloy production samples (564). For the emission spectrometric analysis of gray cast iron sam les, remelting with twice as much iron was recommended 671) while another study of cast iron sampling for spectral analysis discusses the various molds and conditions that will mcwt likely produce an acceptable sample (574)admitting that certain samples would have to be analyzed by chemical methods because of the significant separation of the graphite in the iron. A method and apparatus are described for the use of the sparking profile during emission spectrometric analysis with time and calibration charts to diferentiate and measure the soluble and insoluble concentration of an element (such as Al) in a steel (589). Surface oxide films have a deleterious effect on the propagation of analyte into the electrode gap during spark excitation of metals, and this effect has been shown to be diminished by the addition of hydrogen into the argon shrouding gas (435).
E)
GALLIUM Gallium was determined in iron ores by atomic absorption spectrometry (181) using an oxygen-acetylene flame. For concentrations greater than 0.1 % , the determination can be completed directly on the sample dissolved in mineral acids. For concentrations in the range from 0.001 to 0.1 % , liquidliquid extraction is required to concentrate the analyte. In high-alloy steels, gallium was also determined by atomic absorption in the range of 2.8-20.6% (466).For concentrations less than 5%, a nitrous oxide-acetylene flame was used, and for greater than 5%, an air-acetylene flame was used. Both methods were reported to have good precision and accuracy. 98R
ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
GASES IN METALS A recent English review describes the principals of electrochemical sensors with emphasis on design parameters, electrolyte type, and reference materials (119). Another general review covers methods and apparatus for the determination of H, N, and 0 in steels (126). To aid in the use of measuring devices in the mill, an apparatus has been patented for automatic immersion of electrochemical gas sensors into melts (452).Along these lines, a recent Japanese patent covers the use of a device for bubbling an inert gas through a melt and analyzing the gases being purged and collected with a gas analyzer (381).Several patents and papers have also been issued in which finely milled steel samples are reacted with a flowing H stream to form hydride gases with the nonmetallics present and which subsequently are determined by mass spectrometry (385,402).An interesting approach to local gas analysis uses a narrow electron beam in a high vacuum to effect melting and stirring of a 1mm depth to release gases from the metal for mass spectral determination (382). For bulk analysis of gases in a metal sample, a specially designed resistance heated graphite crucible has been patented (177). A recent Russian paper describes the use of porous A1 nitride as a semipermeable membrane for determining gases in molten steel by vacuum or inert gas extraction (75). Vacuum fusion methods were successfully employed for the determination of H, CO, and N in blast furnace and pig iron slags (128).In some related publications concerned with gas analysis in the ferrous metals industry, the use of infrared detectors for monitoring water vapor evolution from the reduction of iron ores has been reported (315)as has the use of various instruments for furnace atmosphere monitoring (55) and for blast furnace and basic 0 process gas monitoring (317). The use of Zr-oxide-based sensors for flue gas monitoring (279) has been reviewed.
HYDROGEN A specific application of the molten metal inert gas purge system mentioned above has been patented as part of a method for the determination of H in steels (171). Sampling tubes have also been atented for the determination of diffusible and nondiffusiile hydrogen in samples taken from the melt (228). With regard to the sampling of molten steel baths for their hydrogen content, several studies have appeared describing the potential sources of hydrogen loss during sampling (137),the magnitude of the losses that can occur (272)and means for im roving the surface quality of the specimens collected for sulsequent gas analysis (507).Another publication recommends the use of a newly developed disposable vacuum mold in conjunction with a fast H analyzer to obtain accurate measurements of hydrogen content in liquid steel (594). Classical (based on vacuum techniques) and modern methods (carrier gas, SIMS and nuclear reactions) for the determination of hydrogen in steel have been extensively reviewed in a recent paper (476)while two papers describing the Leybold-Heraeus system for steel sampling and analysis by hot extraction have appeared (210,320).The use of the “HYDROS”, a thermal conductivity based analyzer for steel analysis has been compared favorably to conventional H analyzers in another recent instrument review (459).Two types of commercial instruments have reportedly been successfully combined to enable the routine determination of total and diffusible H in steels and in a ferrotitanium by hot extraction (549,550). The measurement of hydrogen in weld metal has been the focus for a number of papers. Numbered in this group is the determination of H in welds by a “thermovac”extraction (5841, a vacuum hot extraction method applied to stainless and Ni-based alloy welds and claddings (log),the use of the apparatus DIN 8572 for the determination of total and diffusible H by carrier gas hot extraction (260),a method for determining the hot extractable H from the molten metal in a ferritic steel weld (19),a study of the parameters that affected results obtained from several laboratory methods (IS0 3690-1977 and Osaka University methods) for the evaluation of initial and diffusible H in weld specimens (219),and, finally, a method for measuring the hydrogen contamination in weld arc plasmas by use of a near-IR emission line of hydrogen (492).The solid electrolyte-H-uranyl phosphate tetrahydrate has been used in the development of electrochemical sensors for the measurement of H activity in steels, welds, and metallic coatings
FERROUS ANALYSIS
(306,361)with apparently Nernstian response. Another paper described the development of a hydrogen detector for monitoring >10 ppb levels of H in high-strength steels (604). Programmed heating in conjunction with a gas chromatograph and thermal conductivity detector has been applied in an apparatus that enables the determination of diffusible H in steel with a lower limit of 5 x IO-' ppm for 2-g specimens (400). Fixed temperature heating in a flowing argon steam has also been used for the evolution of H from steels (271). A similar approach was taken in another paper in which the evolution of H from polycrystalline iron was effected and measured by heating the sample at a constantly increasing rate in a vacuum furnace (536). For the determination of the forms and distribution of hydrogen at grain boundries and in surface films, a high-performance time of flight atom probe was used in the first case (471) and an elastic recoil detection technique with 2.7-MeV helium ions used in the latter (603).
NITROGEN The feasibility of the electrochemical determination of nitrogen in steel melts has been investigated and reportedly been demonstrated in a recent Russian study (37) while for those determinations that require decomposition of the sample, accurate results were obtained by using a combination of levitation melting and gas chromatography(440).A detailed study of the hydrogen hot extraction technique has been published in which conditions were theoretically determined and proven for the successful differentiation of free and precipitated nitrogen in steel particles (401). This type of a determination has been incorporated into an automatic apparatus and proven on several Cr-V and Cr-V steels (545). If the nitrides in a steel have been chemically extracted, for instance, by an iodine-methanol extraction, it has been demonstrated that the residue can be decomposed in molten NaOH and purged with argon and subsequently measured coulometrically (375). For those methods that require a complete dissolution of nitrogen-containing compounds, a mixture of sulfuric and phosphoric acids was recommended tp increase the recovery of nitrogen (281). The use of chemical dissolution, steam distillation, and titration of the evolved ammonia has been incorporated into an automatic nitrogen determinator (370).
OXYGEN A recent literature review in English has concerned itself with basic design considerations of electrochemical 0 probes and has especially touched on polarization effects, tubular electrolyte sensors, and plug-type sensors (201). Principles of 0 sensor use and applicability to various metal melts have been covered in two publications, one in Japanese (138) and the other in English that describes techniques of use, design considerations, and electrolyte stabilit among other topics (199). Experiences ained from a 14 lagoratory study of the best use of existing determination technolo are included in a recent French study (20). Other papers puKshed devoted to the study and use of electrochemical 0 sensors in the steel industry include a discussion of the use of a hood-shaped solid electrolyte cell (304),the construction and use of calcia-stabilized zirconia probes for studying argon and nitrogen stirred low carbon, Al-killed steel (1181, a general review of the measurement and use of oxygen activity in steelmaking (in Czechoslovakian) (2621,a review of new applications of oxygen sensor technology in steelmaking activities in Ja an (351),and a general review of the use of 0 probes in la$e metallurgy with emphasis on Al-killed and Si-Mn-killed-rimmed and semi-killed steels (465). A large body of patents have been issued in the past 2 years that relate to the design and modification of electrochemical probes for the determination of 0 in molten metals, articularly steel. These patents include a zirconia-based proEe coated with a metal oxide powder, an organic binder and flux as needed (172),a closed-end zirconia-magnesia tube sensor in which the tip is filled with an appropriately chosen oxide with the proper 0 partial pressure in relation to the standard 0 material used internally (173), another design of similar nature with details of the preparation of the internal standard metal/metal oxide mixture (390),the design and use of a zirconia-magnesia-based electrolyte 0 sensor, possibly related to the previous reference (391),an 0 probe design that incorporates a coating with a low coefficient of thermal expansion (quartz glass, TaN, AIN, mullite etc.)
8
(525),an 0 sensor with a small inside diameter and thin wall for good low 0 sensitivty (552),the design of a consumable solid electrolyte cell (230),the design of an improved reference electrode using mixtures of Cr-Cr203 (see ref 390 and 391) (353),an electrode design that uses the flame spraying of the active solid electrolyte on a metal rod carrier (333),and the design of a sensor that contains the solid electrolyte applied to a porous reference electrode (324). Papers that have appeared related to the design and modification of existing 0 probe technology include a description of the improvements in electrolyte properties, thermal shock resistance and probe shape for magnesia stabilized zirconia probes (83),the use of a thin alumina insulating tube combined with a stoppered solid electrolyte probe for the continuous measurement of 0 in liquid steel (200) in which a variety of solid electrolytes were appropriate, and the use of an improved probe design that was related to preheat-treatment of the reference electrode materials, and the application of an improved thermal shock-resistant coating on the zirconia tube (348). A relatively new study of the measurement of 0 activity as it relates to C content of the bath in basic oxygen converters was made with the use of two solid electrolyte probes installed on the sublance to minimize the scatter of the measured data (114). A detailed Japanese study has reported that the optimum volume fraction of cubic ZrOz in a magnesia-stabilized zirconia electrolyte was determined to be about 27% to confer the best thermal shock resistance and responsivity properties to the 0 probe (354). Some evidence of the instability of the commonly used CrCr203 reference cell was obtained in a recent Italian study and was attributed to a transformation occurring in the system at about 1653K (140). Another study published in 1983 dealt with the importance of oxygen anion diffusion and the effect of electrolyte thickness on this parameter and its ultimate relationship to measwed electrode potentials. A kinetic model was developed from this study (328). Studies with hafniayttria and zirconia-yttria cells have been reported in two recent Russian papers and cite the agreement of oxygen results with vacuum melting experiments in one case (257) and the need to consider both the electronic component of electrical conductivity and the ionic component for the determination of low levels of 0 with electrochemical sensors (150). A Canadian study has indicated that it is possible to monitor 0 in a tundish by suitable electrode design and by imbedding the sensor in the refractory lining. Oxygen contents were followed reliably for over 15 h in laboratory heats and over 3l/ h in concast tundishes (107). $he performance of the LECO RO 316 oxygen determinator has been evaluated for the measurement of total oxygen and the types of oxides present through the available temperature programming capability of the instrument. Details are given for a special method of characterizing the types of alumina present in a number of steels (510). The reuse of graphite crucibles for the determination of 0 in steels is the subject of a Japanese patent and involves the use of tin to aid in the release of sample beads after each analysis is concluded (528). Another Japanese patent covers a procedure for obtaining drillings of a steel sample under a solvent (Freon 113), evaporation of the solvent in an inert gas, and subsequent analysis by conventional combustion techniques to complete the 0 determination (555). A detailed method has been described for the determination of oxygen in high sulfur steels (0.04-2.8% S) which employs a long (13 h) vacuum fusion decomposition of the sample and subsequent manometric measurement of the various gaseous fractions after suitable trapping steps (161). It has been applied to resulfurized free-cutting steels. 0 present in molten steel has been converted to CO by reaction with C and measurement of the purged gas with an IR-based CO meter (602). For the determination of 0 and C on the fractured of specimens, a device has been developed to allow the fracturing of the specimen in a vacuum and transfer to a second chamber for ion microanalysis of sputtered ions by mass spectrometry (378).
HALOGENS Chemically treated steel samples were placed in a hot aqueous solution of sodium hydroxide to dissolve the surface films, and the extracted solution was analyzed by liquid-liquid chromatography (227). A new combustion tube has been ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
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designed for the simultaneous determination of the halogens as well as carbon, hydrogen, and sulfur in coal, coke, and steel (34). The tube is said to be leak-free at the ground joint and still permits rapid and convenient sample introduction. Fluorine in chromium plating baths used for the production of TFS is automatically monitored by using ion-selective electrodes (383, 384). Fluoride is added to the bath automatically as required. Neutron activation was used to determine the fluorine content of complex iron ores (145),while Auger spectroscopy was applied to the measurement of chlorine in grain boundaries of stainless steel (40, 41). An argon-flushed optical path has been used to enable the measurement of iodine in iron and steel by ICP emission spectrometry (160).
INDIUM, MERCURY, AND THALLIUM Indium and thallium present at trace levels in iron and iron ores have been determined by atomic absorption spectrometry after dissolution, complexation with ammonium dioethyldithiophosphate, and filtering through an activated carboncoated filter to concentrate the analytes (36). For the neutron activation measurement of mercury in steels at the artsper-billion level, selenium interferencemust be removed Before the determination can be completed (457). Thallium was reportedly determined in steels by a combination of a liquid-liquid extraction of the thallium and subsequent flowinjection introduction of the extract into an air-acetylene flame for atomic absorption spectrometric analysis (204).
IRON Several papers appeared describing the spectrophotometric determination of iron in ores using the following complexing agents: 5-chloro-2,4-dihydroxypropiophenone(569), 2carboxy-2’-hydrox 3’,5’-dimethylazaobenzene-4-sulfonic acid (319),l-phenyl-3-t&obenzoylthiocarbamide(190),thioglycolic acid (362),and phenoxyacetylacetophenone (13). Sensitivities ranged from 0.002 to 0.029 pg/mL Fe. In steel, complexing agents used for color development were N-hydroxy-N-mtolyl-N-m-tol~l-N-(3,4-dimethyl)phenylbenzamidine (487), 2,4,6-tri(2-pyridyl)-l,3,5-triazine and tetrabromophenol blue (561), N-phenylcinnamohydroxamic acid (691, and ophenanthroline (437). In the last application, iron corrosion rates in acid solutions were investigated. X-ray spectrometry-PIXE and Rutherford backscattering spectrometry were used to determine the sputtering yield of iron, nickel, and chromium from thin films of stainless steels bombarded with helium atoms (470,554). Thin iron-nickel foils were analyzed by depth profiling (462). Energy dispersive X-ray spectrometry was reportedly used to analyze steel samples without reference to standdrds (478,479) and the results were independent of geometric form or size and were obtained rapidly. Iron present as the oxide was determined in blast-furnace and open-hearth slags after fusion with lithium tetraborate (364). Atomic absorption spectrometry was used to determine iron in ores and slags and cesium and lanthanum additions were made to eliminate chemical and ionization interferences in the flame (477). Electroplated iron-chromium deposits were analyzed by stripping the electroplate from the substrate with 10 N hydrochloric acid and completing the analysis with atomic absorption spectrometry (282). Iron has been titrated accurately in ores by using ascorbic acid in a sulfuric acid medium and benzohydroxamic acid as an indicator (4) and with titanium chloride and Neutral red indicator (97). The distribution of iron in the metallic, divalent, and trivalent states in ores and ore pellets has been determined by electrochemistry (434) and by oscillopolargraphy (72). Electrochemical methods were also employed for the measurement of iron in ferromolybdenum (234) and ferrovanadium (314). Neutron activation was also investigated for the determination of total iron in ores (148, 410).
LEAD Trace Pb in steel has been determined spectrophotometrically using KI and crystal violet as the reagents. A protective colloid was used to stabilize the complex (615). Of three spectral methods studied, X-ray fluorescence techniques were preferred for the determination of micro levels of lead in construction steels (143) although it has also been reported that the vacuum-UV region is acceptable for the ICP deterlOOR
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ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
inination of lead in steel and iron if the optical path is argon flushed (160). Minor and trace levels of P b in ores and steels have been determined by atomic absorption spectrometry following an ion-exchange separation on an anion column ( 4 7 4 , in ores after separation of the Pb traces on a C-coated filter and atomic absorption spectrometric determination of the trace elements absorbed on the dissolved filter (36),and in steels after a TOP0 extraction and atomic absorption analysis of the extract (204). Electrothermal atomizatioil has been required to measure subtraces of Pb in ferrous alloys and steels after acid dissolution (443), although direct electrothermal atomization in a graphite-cup cuvette has also been used for the determination of Pb in single particles of steel (534). Two peaks resulted from the presence of analyte both at the grain boundry and within the grain. Lead has also been determined by electrothermal atomic absorption spectrometry in steels and cast iron samples after fusion and acid dissolution of the sample (570) and in dissolved steel in solution by a pulsednebulization flame atomic absorption spectrometric method (624). Pulsed introduction allows the aspiration of more concentrated sample solutions. Ores have been successfully analyzed for trace elements such as lead by application of atomic absorption spectrometry if the iron is first removed by liquid-liquid extraction (209). P b in ores, carbonyl iron, and cast iron can also be determined by atomic absorption spectrometry if the lead is first separated by precipitation with thioacetamide (115). Sample preparation methods have been studied and reviewed with regard to the determination of Pb by either atomic absorption spectrometry or photometric methods (311). Iron, cast iron, low- and high-alloy steels, and ferroalloys were covered.
MAGNESIUM A new spectrophotometric method for the determination of 1% nickel by using the color of the dimethylglyoxime complex after a specific portion of the steel has been dissolve by acid attack (229). Electrophoreticseparations were used to quantitatively isolate nickel from dissolved steel samples and the isolate was treated directly with dimethyl loxime for the color measurement (464). Triethanolamine 8,proven to be an effective masking agent during the spectrophotometric determination of Ni with dimethylgloxime in high-alloy steels (453). Other spectrophotometric methods for the determination of Ni in steels that have appeared in the literature are those that use the formation of the ternary complex of Ni with cardion and 1,lOhenanthroline (496) and the ternary with 2-(6-bromo-2~enzothiazolylazo)-5-diethylaminophenol and Tween-80 (625). The latter method requires a preliminary extraction of the Ni. Ni in stainless steels has reportedly been determined gravimetrically by quantitative precipitation with 2hydroxy-1-naphthaldoximebetween pH 4 and 9 (270). A sensitive polarographic method has been described that used the catalytic reduction wave of the Ni-dimethylglyoxime complex a t about pH 9 for steel analysis (588). Ni in alloy steels has also been determined by an amperometric titration with dithiocarbamate a t a rotating Pt microelectrode (568) and by a compleximetric titration with EDTA usin 2 (5bromo-2-pyridylazo)-5-diethylaminophenol as the inticat or ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
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(607). In order to prepare iron ores samples for the determination of trace levels of Ni by either atomic absorption spectrometry or inductively cou led plasma emission spectrometry, the iron is first removecf by liquid-liquid extraction and the aqueous phase concentrated before analysis (209), while anion exchange chromatography is used for the preliminary separation step in trace Ni methods used for the analysis of iron ores (474) and the analysis of manganese nodules (254)by atomic absorption spectrometry. Recently, a universal atomic absorption spectrometric method has been developed for the determination of 14 elements, including Ni, in slags, ores, metals, and other materials (477). Relative standard deviations of from 1.4 to 5% were cited in a study of a computer-controlled direct-reading emission spectrometer for the determination of Ni and eight other elements in steels (1821,while two studies have been published comparing hollow cathode and glow discharge radiation sources for the determination of alloying elements and traces in steels in one case (56) and the sputtering parameters of importance in the glow discharge emission spectrometric analysis of some ternary Fe-based alloys and some common stainless steels (576). X-ray fluorescence analysis of Fe-Ni alloy wires was compared to wet chemical methods, and the absolute error obtained was 0.006% in steel by ICP excitation with an echelle monochromator has been enhanced by using wavelength modulation and lock-in amplification to eliminate background interferences (597). Details of the emission spectrometric determination of a number of elements including P by using a vacuum quantometer have been given in a recent Russian paper (331),while a more recent study of the Grimm lamp for the spectrochemical analysis of steel has revealed that the working curves for the determination of P depend on the kind of steel being analyzed (350). Dc arc volatilization and aerosol transfer of the volatile material for subsequent excitation in a capillary arc unit have been combined to produce a mobile spectrometer successfully used for grading steels with regard to their P content (546). Two recent studies have appeared respectively describing the use of computer-controlled XRF for the rapid yet accurate determination of several elements including P in stainless steels (106)and the effect of sample matrix on the XRF analysis of cast irons for their P content (386).
RARE EARTHS Cerium has been separated from ferrous sample solutions by sorption on an azoantipyrine sorbent and released to form an Arsenazo complex for a spectrophotometric determination of the Ce (30),while extraction with TOP0 has also been used to precede an Arsenazo I11 finish for the analysis of steels and cast iron for their Y, La, Ce, Pr, and Nd content (202). The latter four elements were also separated on a Dowex 1XB column before a comparable Arsenazo I11 spectrophotometric determination of these rare earths (499). A cationic resin, Zerolite-225, has also been used in the same manner to isolate the rare earths and yttrium to enable an Azoarsine I11 spec-
FERROUS ANALYSIS
trophotometric finish (71). In a recent study details have appeared on the use of various ligand buffer masking systems for enhancing the spectrophotometric determination of rare earths with the reagents Arsenazo 111, Dicarboxyarsenazo 111, Chlorophosphonazo 111, carboxynitrazo, and Semixylenol Orange-cetylpyridinium bromide (74). For the direct determination of microamounts of Ce group rare earths in steels, the use of the p-acetylarsenazo either alone (614) or as a derivative of bisazochromotropicacid was recommended (611), while another group recommended a procedure using Chlorophosphonazo-mNfor both totalRE and the Ce group (147). In the presence of tetradecylpyridinium chloride, amino-J acid chlorophosphonazo reacts to form a blue complex with the rare earths and has been used satisfactorily for steel analysis (293). RE metals in nodular cast iron have been complexed and measured spectrophotometrically with Chlorophosphonazo-m-sulfonic acid (307). A new reagent, Nitrophosphonazo-mA has been shown to be highly selective and sensitive for the determination of the Ce group directly in the presence of the Y subgroup RE elements and has been applied to cast irons and steels effectively (295). Microamounts of the Cegroup elements in high-alloy steels have been determined by use of the ion association complexes of rn-Formylchlorophosphonazo-RE and cetyltrimethylammonium bromide (303). Ce in cast iron and steels has been separated by copreci itation with La oxalate, the precipitate oxidized, and Ce(1V) measured spectrophotometrically (205) according to a recent publication. Fe ores have been successfully assayed for their RE content by a preliminary extraction of the lanthanides with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone followed by an Arsenazo I11 colorimetric determination (411). Low levels of Ce were determined kinetically in a ferroalloy by the effect of Ce on the reaction rate of the UV-radiationinduced reduction of the ion complex Fez(phen)4(OH)$+(393). La and Ce were reported to be determinable in a series of alloys by using the h e n a z o 111complex to determine the total La-Ce response and then decomposing the Ce-Arsenazo complex with permanganate and measuring the residual La response (511). y group rare earth elements (Y, Er, Yb, Lu, Dy, Gd) have been determined in cast irons, alloy steels, and ores by using the reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a weakly alkaline medium. Interference from the Ce subgroup is removed by the addition of F (585). In another procedure, coprecipitation of the cerium present in iron and steel with LaF and subsequent workup of the ashed, fused and dissolved precipitate for a spectrophotometric analysis with o-tolidine has been described (252). Inductively coupled plasma atomic emission spectrometry has been applied to the determination of major and minor amounts of Ce, La, Nd, and Pr in Fe-based alloys. Detection limits, spectral interferences, and analytical results in comparison to other techniques are discussed (116). In another published report, optimum conditions for the use of a hollow cathode source to determine Ce, Y, La, and Dy a t the 0.001 to 1.0% level in steel have been established (58). Excitation, detection, and surface finish parameters were evaluated in a recent paper describing the use of wavelength-dispersiveXRF spectrometry for the determination of Ce and La in nodular cast iron (11). Two other studies of this analytical technique recommend the use of ion-exchange separation of the rare earths yttrium (77) and Ce, La, Nd, and Pr (211) from steels prior to direct excitation of the ion-exchange resin to finish the analysis, while for Cr/Ni alloys, a liquid-liquid extraction is preferred (77) for the separation.
ti;
SAMPLING AND PREPARATION OF SAMPLES A sufficient number of papers have appeared covering various aspects of the sampling process as it pertains to ferrous analysis that they warrant special mention. First on the list are two methods that allow continuous measurement of macrosample compositional variations either with an emission spectral excitation of a moving slab sample and analysis of the emited spectrum (373) or by scanning the sample with an electron beam and measuring the characteristic X-rays with an energy dispersive detector (371). Another recent Japanese patent describes the use of an apparatus for spectrally analyzing the light produced at a molten steel surface by the reaction of oxygen in the probe with carbon in the steel (403).
The method has been used for the determination of carbon. Several reports have been concerned with the sampling of molten metal in order to produce solid, homogeneous, and representative samples; these include a BSC BISPA report on sampling (96),a sampler design that provi es a sample for aluminum (and other elements) analysis almost free of oxide interference (514),a disposable sampling device for producing disks for X-ray analysis ( 4 0 , an evacuated, specially shaped quartz molten steel sampler (389),and a molten metal sampler with a chemically coated interior that confers corrosion resistance, is insoluble in the sample material, and releases the sample readily (377). The automation of sample preparation for process control is discussed in a recent publication (158). In order to prepare thin metal specimens for emission spectrometric analysis, procedures have been patented for the mounting of the sample in a tube with a magnet to hold it while it is being mechanically polished (387) or for mounting it on a solid substrate with molten tin and subsequently polishing the surface exposed to be analyzed spectrometrically (388). For the rapid and routine inductively coupled plasma atomic emission spectrometric determination of major and minor constituents in steels, a high-temperature and high-pressure acid decomposition procedure has been found to be very acceptable (113). The procedure is free of volatilization losses and presents a salt-free matrix for analysis. According to a recent Japanese patent, fine powder samples can be satisfactorily analyzed by XRF techniques by bonding the sample to a substrate with an adhesive (380). Another patent describes the use of an oxidizing flux prepared especially to prevent alloying of any metal present in an ore or slag sample with the Pt crucible by oxidizing the metal at a lower temperature than alloying occurs (379). Sample preparation procedures have been described as applied to the analysis of ores, agglomerates,slags, and refractories (108) and complex ferroalloys (212). Both required a preliminary calcining step and then fusion with lithium tetraborate. In the same vein, a detailed study was performed and reported in which the effects of particle size, sample-to-flux ratio, fusion temperature, and fusion period were investigated for a series of 32 Fe ore standards (112). The samples were analyzed by XRF. Several Japanese patents relate to the specification of conditions that must be met to enable the rapid high-precision XRF analysis of ores and slags by the glass bead method (368, 529). In the latter patent, corrections for the loss of moisture and gain of oxygen during fusion are determined. The samplin and analysis of cast steels and cast iron was the subject o f t ree recent papers. In the first, optimal conditions were established for taking Cu-mold samples of high-alloy cast steels for subsequent X-ray spectrometric analysis (231). The latter two covered melting and sampling of gray and ductile cast iron for emission spectrochemical analysis (62)and the potential for carbon inhomogeniety as determined by spark-sourceemission spectrochemical analysis in improperly cast samples of malleable iron (120). In the area of scrap sorting and analysis of steel products without sampling, most of the published effort has been devoted to the use of mobile spectrometers although one paper described the use of an electrochemical probe for transferring a small, representative sample electrolytically to a sensitized paper (12). The elements Fe, Ni, Cr, Au, and Cu were detected with the procedure. The classification of C steels and low alloy steels for carbon content with two commercially available mobile emission spectrometers was found to be limited to the range 0.15-0.2% C in one paper (248) although another system developed with the aid of the European Coal and Steel Community has shown that a dc arc generated aerosol-based device can by used to produce remote (15 m) analyses comparable to laboratory-produced results (547,548). Combination of a thermal EMF alloy separator, portable spectroscope, and a portable fluorescent X-ray analyzer has been reportedly successful in sorting mixed Ni-alloy, super alloy, and stainless steel scrap (50,460),while just an isotope source X-ray fluorescence spectrometer has been used for the identification of and measurement of the chemical composition of various ferrous, Ni, and Co alloys (68).
d
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SECOND PHASES AND INCLUSIONS A number of reviews have appeared that summarize the methods and instrumentation used for phase analysis and the ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
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composition of phases isolated from steels. These include a review of methods used for high-speed steels (273), a methodical study of precipitate behavior through a quantitative study with microchemical analytical techniques (301),a review of various isolation techniques and methods of analysis of the isolates (357),several progress reports from the Joint Research Society of the Iron & Steel Institute of Japan on the certification of standards for the isolation of carbides from steel (221) and the isolation and determination of nitrides and carbides in steels (358), the application of electrochemical methods of isolation of second phases from steels and alloys (48.9, and a review of the last 30 years of rogress in the isolation and analysis of sulfide inclusions (562y Three papers deal with the analysis of isolated residues from steel with regard to their metallic content and include procedures for the use of AAS (Mn, Cr, Fe, Ca, Mg) (44),the use of hollow cathode discharge excitation for the determination of both the isolated components and the dissolved matrix elements (Cr, Mn, Mo, Si, V) (57), and the use of plasma emission spectrometry for the analysis of electrochemically separated precipitates (Al, B, Ce, Co, Cr, Fe, Mn, Mo, Nb, Ti, V, Zr) (167). Vanadium in electrochemically prepared residues was quantitatively determined by XRF spectrometry by the excitation of the samples combined with cellulose in briquets (508). A recent Japanese patent describes a method and apparatus for separating cementite from precipitates formed in steel by use of a sonically vibrated magnet (224) while another patent covers the use of a bag to retrieve inclusions isolated during electrolytic extraction techniques being used for quality control of continuously cast steel (372). A number of papers have appeared describing the use of energy dispersive X-ray analysis or electron energy loss spectroscopy for the in situ study of second phase particles in steels; these include applications to the determination of Fe/Cr ratios (80, go), fine precipitates of Cr oxide, nitride, and carbides (605),carbides and carbonitrides of vanadium (98),and titanium carbide phases (326). Microprobe studies were reported covering the origin of nonmetallic inclusions in steels (341)with emphasis on the slags and refractories used in steel making, and for other inclusions such as MnS (374). STEM-EDX microanalytical techniques were applied in studies of the segregation of elements in thin foils (94) and for the determination of the composition of a series of eutectic carbides (Ni, Fe, Cr, Mo, V) in cast W-Mo high-speed steels (573). Procedures have recently been described for the a plication of SIMS technology for the study of recipitates Al, V, C) in microalloyed and C steels (355f In a recent study of chemical and electrochemical methods, it was determined that although MOBcan be isolated quantitatively, most boride inclusions can only be deduced by difference (392). The determination of the various forms of nitrogen in steels has been critically studied and the preferred sequence of determinations is (1)total N, (2) free N, (3) nitride N, (4) A1 nitride N, (5) acid-soluble N, and ( 6 ) Bee hly N (259). An extensive procedure has been developed anLf described for the determination of the unstable nitrides and dissolved nitrogen in carbonitrided layers in alloy steels (363). Another study gives details for the specific determination of A1 nitride isolated along with other inclusions separated from steels (288). Hydrogen extraction at selected temperatures has been utilized for the discrimination and determination of the labile N and N in the AlN in iron alloys (287) while a combination of vacuum extraction and chemical isolation methods has been developed for the differential determination of A1 and Si nitrides in transformer steels (289). Electrochemical separation of oxide residues, fluxing with KOH, and analysis of a water leach of the flux cake by AAS have been used for the determination of Ca and Mg in oxides from steel and cast iron (366). In another study, a combination of chemical treatments after electrochemical isolation of an oxide residue has been used to selectively separate the various oxidic components for final analysis (553). Isotope-dilution mass spectrometry was used to characterized the sulfur present in some steel reference materials, with some values being influenced by the amount of manganese present (587). In this study, the sulfur was converted predominantly to sulfate both in an open beaker and in sealed tube dissoluton methods. By use of the total S values and the stepwise determination of S by hydrogen reduction of the
(d,
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S, FeS, and MnS to HzS, a measure of the stable sulfides such as CaS and the rare earth sulfides can be effected (369). The distribution of cerium in steels has been discerned by a coupling of radioactive tracer labeling and an analysis of the electrolyticallyisolated second phases and the dissolved matrix (153,593). In another study of the distribution of rare earths in the various phases of construction steels, a series of chemical treatment steps were used to selectively decompose a residue isolated by anodic dissolution (436). Several Cr-Mo steels were characterized as to their second-phase content of carbides and carbonitrides by first electrochemically separating the compounds of interest and subjecting the residues to chemical differentiation (600,563) or to a combined SEM-EDXRF (qualitative) and spectrophotometric (quantitative) analysis for the determination of the various components present (217). Niobium present in the carbonitride phase of a steel containing 0.6 to 0.9% Nb has been determined by a chemical dissolution of the steel and analysis of the isolated residue following various heat treatments of the steel (76). SELENIUM AND TELLURIUM Atomic absorption spectrometry was used to measure selenium in transformer steels by electrothermal atomization (498) and tellurium in low-alloy steel after preconcentration by liquid-liquid extraction. Both elements were determined in stainless steel and cast iron by an isotope-dilution sparksource mass spectrometric method after they had been preconcentrated and collected with a gold carrier (240).
TANTALUM A potentiometric titration procedure that used a hexafluorotantalate ion selective electrode was applied to the determination of Ta in steel. Cetylpyridinium chloride was recommended as the most suitable titrant (617). Extraction spectrophotometry of an ion association complex of Ta and malachite green in the presence of HF has been used for steel analysis (265). Boron interference was eliminated by a preliminary separation of the Ta with Zr phenylarsonate.
SILICON Flame atomic absorption methods were discussed (327) for the determination of silicon up to 1% in steel. A general procedure was proposed using NBS standards for calibration. Silicon and phosphorus in steel alloys were simultaneously determined spectrophotometrically (542) by measuring absorbances at 700 and 790 nm, which are related to reduced a-molybdosilicic acid and @-molybdophosphoricacid, and solving two simultaneous equations. In similar methods, slags and steel may be analyzed for silicon by dissolving 20 mg of the sample in mineral acid, forming silicomolybdic acid and finishing the measurement colorimetrically (162, 163). Silicon in steel was also determined by inductively coupled plasma in conjunction with optical emission spectrometry by forming the volatile chloride with carbon tetrachloride in a sealed glass ampule and transferring the chlorides to the plasma torch (277). X-ray fluorescencespectrometry has been used for this same determination in stainless steel (IO@, cast iron (386),and slag (364). Slag samples were fused in lithium tetraborate before analysis. Ferrosilicon may be analyzed by acidimetric titration of the hydroxyl ions formed when fluoride ions react with silicic acid (267). In another procedure that uses the properties of the fluoride compound, steel samples are dissolved in vacuum in a graphite crucible containing nickel and nickel fluoride. Silicon fluoride is then extracted and the silicon determined by mass spectrometry (218). After separation of iron, silicon was determined in iron and steel by differential pulse polarography as described in a recent publication (183). In the presence of butanone, low concentrations of silicon react with ammonium molybdate to form P-12-molybdosilicicacid and the determination of silicon is completed as above, On-stream monitoring of silicon by neutron activation analysis during the benefication of lowgrade iron ore slurries has been reported (47). Standard pellet samples have been prepared for this determination (110),but the silicon particles must be crushed to less than 0.16 nm to obtain accurate results.
SILVER Liquid-liquid extraction has been used to preconcentrate silver from low-alloy and high-alloy steel prior to an atomic
FERROUS ANALYSIS
absorption spectrometric determination (204),while electrothermal atomization has been ap lied to steels directly (302). The products of mineral aci dissolution of several standard ferrous alloys and steels have also been subjected to flame atomic absorption spectrometry for the determination of the silver (443). Considerably lower detection limits for the determination of silver by AAS were obtained by using ulse-nebulization atomization of the dissolved steel samples gy virtue of the ability to use more concentrated solutions for analysis (624). For the determination of trace levels of Ag in steels ion association complexes of Ag, I-, and Rhodamine B in the presence of poly(viny1alcohol) (299)and Ag, 1,4,8,11-tetrathiacyclotetradecane, and picrate ion in 1,2-dichloroethane (467)have been recommended. In ores, silver has been determined spectrophotometrically as a ternary complex with o-phenanthroline and bromophenol red (441).
B
STANDARDS The work of the Canadian certified materials project (CCRMP) has been summarized and data given on the preparation and certification of a number of standards (516) including a reference iron ore (517). Carbon was determined in 31 European reference steel standards and the results from 28 showed that the certified values were high by an average of 27 pg/g (515).A series of Russian publications describes the preparation and certification of ferromanganese, iron ore, and stainless steel standards (519)and FeP, cast iron, low alloy steel, and steel (520,521).Another paper from Russia highlighted the development, certification, and nomenclature of standard reference materials from the Central Scientific Research Institute of Ferrous Metallurgy (428).Procedures are given for the preparation of pressed reference samples to be used when matrix effects cause problems in the determination of trace levels of impurities by laser microspectral methods (458).Two Hungarian patents describe a detailed melting, casting, forging and remelting process for the production of steel standards for emission, X-ray, or laser spectrometric quality control (456)and the production of alloy chip samples from the standards prepared as above for subsequent use as wet chemical standards (455).
STRONTIUM Atomic absorption spectrometry has been used for the determination of Sr in coals, ores, and slags after chemical and ionization interferences were minimized by the addition of lanthanum and cesium (477). Both atomic absorption spectrometry and ICP-OES were applied to the determination of strontium in ores after the potentially interfering iron was removed by a preliminary extraction (209).
SULFUR For the determination of traces of S in steels, an indirect potentiometric method has been described in which the excess cadmium ion remaining after the sulfide has been precipitated is titrated with EDTA using a Cd-ISE (61).Another procedure for the determination of total S in slags and ores utilized the back titration of excess iodine after reaction with evolved H2S (formed as a result of a treatment with Sn(I1) and H,PO,) from the sample (188). For trace amounts of S below 5 ppm in Fe and steel, the methylene blue procedure for H2Shas been extended by extraction as an ion pair with perchlorate to achieve lower limits (359).The determination of nonmetallics in steels such as sulfur, has been accomplished by heating the sample in a hydrogen stream and introducing a portion of the evolved gas into a mass spectrometer for analysis (385,402). Phases can reportedly be distinguished by the tem erature ran e of evolution. A number of procedures have !,en descri ed in which isoto e dilution-spark-source mass spectrometry has been appied to the determination of sulfur in ferroalloys, iron ore, and pig iron Fe-based alloys (421,4221, (468),and standard steels (50,587). In a study of the application of XRF analysis to the determination of light elements such as s, matrix effects and surface roughness strongly influenced the results obtained (386). Sulfur in pig iron has reportedly been determined with low-voltage spark discharge excitation after the initial spark instability disappears (223),while details have been given for the determination of S in open-hearth steels by using a vac-
%
uum quantometer (331). A study of the application of Grimm-glow discharge emission spectrochemical analysis for the determination of S in a variety of steels has indicated that different working curves will be needed for each steel analyzed (350). Methods for the determination of sulfur in Fe and steels (160),steels (186),and pig iron (269),all have in common the use of ICP excitation with either an evacuated or argon-purged optical path. Aerosol emission spectroscopy has been incorporated into a portable emission spectrometer that has allowed the determination of sulfur in steels within a 10 m radius of the analyzer (546). The modifications of a Leco IR 32 sulfur analvzer were evaluated in a recent paper describing 8 years of gxperience with the instrument (480),while experiences with the application of the Stroehlein CS-MAT 900 analyzer for the analysis of steel, cast, and pig iron and powdered samples have also been given recently (18). New types of sulfur analyzers in combination with a synthetic method of calibration have permitted analyses for S below the 10 ppm level in steels (249). In another paper concerned with the combustion determination of S in cokes, coal, and steels, modifications in the combustion tube design are described that allow very convenient introduction and withdrawal of sample boats without the usual leakage around the ground joint (312). A recent J a anese patent covered the development of a combustion aiffor use during the determination of S in steels and other materials (335).The material consists of a vacuum pelletized mixture of Sn and W 0 3 powder.
TIN The evolution of tin hydride from steels by treatment with borohydride has been used to isolate this element prior to a spectrophotometric determination with phenylfluorone (178). Microamounts of tin in steels, alloys, and pure metal have also been determined directly by using one of several possible ternary compounds of Sn(IV), salicylfluorone, and cetylmethylammonium bromide (CTMAB) (596) or o-nitrophenylfluorone and CTMAB (493).A combination extraction-differential pulse polarographic procedure has been employed for the determination of tin at the parts-per-million level in nuclear alloy steels with a recovery of 92% (291). Tin has also been assayed in iron and steel directly by atomic absorption spectrometry after acid dissolution (159), after extraction with TOP0 and subsequent analysis of the extract with pulsed introduction into a nitrous oxideacetylene flame (204)and after separation from pig iron samples by hydride generation and atomization from a heated chamber (308).In a study of three spectrochemical techniques for the determination of a number of microimpurities including tin in steel, XRF was recommended as the most promising from the standpont of reproducibility and range (143).This conclusion was shared in another published study of the applicability of XRF to iron and steel analysis (194). Tin has also been determined directly in cast iron and steel by DC arc excitation-emission spectroscopy (3161,with an argon-purged ICP vacuum emission spectrometer (160),and by evolution of tin hydride into an ICP source for spectral analysis (352,509).
TITANIUM Atomic absorption methods were developed for the determination of titanium in ores (209)after separating the iron by liquid-liquid extraction with i-BuCOMe and in steel (159) by dissolving the sample in aqua regia and perchloric acid, adding aluminum to prevent interferences and completing the determination with a nitrous oxide-acetylene flame. Several spectrophotometricmethods were developed for this determination in steel, alloy steels, and cast iron using dibromophenylfluorone and cetylpyridinium bromide (297,592, 6181,Sulfonitrazo E (406),chlorophosphonazo I (595,345), dibromophenylfluorone (73),and salicylfluorone (495) as complexing agents. Ti was also determined in ores with chromotropic acid and diantipyrylmethane (581)as a complexing agent and after separation on an ion-exchangecolumn packed with AGS-768 resin (474). Point to plane optical emission spectrometry has been used for the determination of Ti in steels (182,331) as has the determination of its distribution in weld metal (396).ICP has been applied to the measurement of Ti compounds in steel (186)while an ICP source with an argon-purged optical path ANALYTICAL CHEMISTRY, VOL. 57, NO. 5, APRIL 1985
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has been used with a vacuum emission spectrometer for the determination of Ti in pi iron (269). X-ray fluorescence spectrometry was reporte ly applied to the accurate determination of Ti in steels from trace levels up to about 0.1% concentrations (194, 396). Another trace method for the determination of Ti in carbon steels was based on the use of differential pulse polarography (606). Several surface analytical methods have been described for the measurement of Ti in oxide layers by Auger electron spectroscopy (481),for the determination of Ti hydride with a time-of-fli ht atom-probe field ion microscope (471),and in implante layers in steel by secondary ion mass spectroscopy (135).
d
d
TUNGSTEN Microgram amounts of W can be extracted and spectrophotometrically determined with either phenylfluorone or salicylfluorone in chloroform at the 0.42% level in steels (21). With appropriate masking agents, the cetylpyridinium-Wsalicylfluoronate complex enables the direct spectrophotometric determination of W in refractory steels (360) while a W(V) thiocyanate extraction and ion association with phenyltrimethylammonium bromide serve to form a colored complex that has been used for the determination of 0.003 to 2.4% W in steels (432). Cetyltrimethylammoniumbromide, salicylfluorone, and W also form a 1:2:4 complex that can be used for alloy analysis at the 0 to 25 pg level (494). Tungsten at
