Review of Fundamental DeveloDments in Analvsis
Emission Flame Photometry Marvin Margoshes, National Bureau o f Standards, Washington, D. C.
D
the period covered in this review, the beginning of 1960 through February 1962, there has been some change in the emphasis of research in flame photometry. The interest in high temperature flames, such as cyanogen-oxygen, has lessened, while the application of organic solvents as a means of improving sensitivity has become more general. Methods have been developed for elimination of some anion interferences by means of releasing agents ahich prevent the formation of refractory compounds of the analytes. A number of papers on chemiluminescence have been presented a t meetings, although little of this information has yet appeared in print. The determination of sodium and potassium is still by far the most common use made of flame photometry. Because this area of application is so n-ell established, very few of the papers reporting on sodium and potassium determinations are cited in this review. URIKG
BOOKS AND REVIEWS
Four new or revised books on flame photometry h a w been pitblished in the past two years. TIYOof t h e are in English. The one by Dean (21) includes information on the flame source and on othcr equipment. as ~ 1 as1detailed discuqsions of the characteristics of the individual elements in flames. The other book in English (81) is a translation from the Russian n-ork by Poluektov. Two books are in German. The one by Herrniann and Alkemade (66)is a revision of an earlier treatise b y Herrmann. The other new book is b y Schuhknecht (112), the designer of the first commercial flame photometer. clopedia of Spectroscopy” several articles on flame photometry. The one by Gilbert (pp. 346-62) includes one of the fen- discussions of chemiluminescence which has as yet been published. A new edition of “hletliods for Emission Spectrochemical Analysis” ( 3 ) includes suggested practices for flame photometry as well as several specific analytical applications. Gilbert (44) has published a revised table of the flame emission spectra of 6G elements in oxyhydrogen, oxy-acetylene, and air-hydrogen flames with aqueous and organic solvrnts.
Reviews of recent developments in flame photometry have been written by Ohyagi (79), Pungor ( g o ) , Dean (26), Britske ( I S ) , and Gilbert (43). Reviews b y Fischer and Kropp (38) and Margoshes (70) are concerned chiefly with sources of error in flame excitation. Navrodineanu (74) has discussed atomization and the structure and temperature of flame sources. Margoshes (71) has written a n introductory chapter for biological research workers.
strument by placing a 2000-pf. capacitor across the ammeter terminals. Mathieu and Carson (73) use a n air-jet stirrer to agitate the sample being introduced into the burner, allorving continuous mising of solutions during the analysis. Stognil (118) obtained a patent on a burner for liquid fuels. Robinson (103) used a modified Beckman burner to study the properties of the cyanogenoxygen flame. STUDIES OF INDIVIDUAL ELEMENTS
EQUIPMENT
A recording flame photometer is described by James and Fisher (57). Poluektov, Popova, and Ovchar (87) constructed a recording instrument based on a Russian-made monochromator, and Poluektov and Nikonova (84) applied this instrument to the determination of the rare earths. A flame photometer incorporating background correction either by means of a n auxiliary photomultiplier vien ing the background or by means of subtraction of a constant d.-c. signal has been built b y Davis et ul. (19); provision is also made for an internal standard. Isreeli, Pelavin, and Kessler (5:) describe the design and operation of a flame photometer for the continuous determination of sodium and potassium; the pretrcatnient of the samples and the final determinations are performed automatically. Ivanov (66) has descrihcd a filter pliotomcter for the determination of potassium. sodium, calcium. mngnesiuin, lithium, strontium, cesium, barium, arid other elements using a n acetone-air flame. Hinde (65) designed a multichannel instrument which automatically cornpensatcs for some interelement rffects by means of the signal from a detector monitoring the interfering elcment. Euley (53) has obtained a patcmt on modifications to the Beckman DU flame spectrophotometer to integrate tlie signal from the detector over a period of time. A conductivity switch connects and disconnects the integrating circuit as the sample is introduced and removed. A signal from a blank solution can also be integrated and then automatically subtracted from the signal from the sample to compensate for background. hIathieu and Burtch (72) rcduced meter fluctuations in the Beckman DU in-
Several workers have presented detailed studies of the emission characteristics of individual elements or small groups of related elementas. The properties of the alkali elements in thf. flame were reexamined by Pungor and Zapp (97). Pungor and Thege (93)studied the emission characteristics of magnesium in a n oxy-hydrogen flame as affected by ethyl alcohol and a number of acids. They conclude that the bands a t 372 and 395 mp are emitted by hfg(OH)2 and that the only effect of tlie added compounds is to a1t.r the eytent of hydrolysis of thiq molecule. Dean et al. (25) h v e exaniincd the line and band spectra of barium in ouyhydrogen and oxy-acrtylene flames, including the effects of varjing gas f l o r , organic solvcnts, and aiiion and cation interferences. The determination of barium and strontium 1)- flanic photometry has been d e c r i b d by Pungor, Zapp, and Thege (9,Q). >hcllcnberqcr et al. (114) have studied the effects of sodium, potassium, and niaqnwium on the emission of light 1ry rubitliuni in an oxy-acetylene flamc. Sodium and POtassiurri had an dianc.inp effwt, while magnesium depres-erl the emission; addition of ‘in e x c ~ c bof pot samples is i w o m n i e n d ~ d . Fallrikova (34) obsrr.crd an enhancement of cesium emission in the prewnce of pot:wiiini. ’These enhanceintats niay he re1:ited to changes in ionization equilibria (see Interference Plienoniena. helon ). Dvofak ( S I ) describes thfl effecats of a number of cations and anions on the emission characteristics of cesium and rubidium. Konopicky and Schmidt (61)observed a specific cnhancernent of emission of aluminum in the presence of hydrofluoric acid. The enhancement could VOL. 34, NO. 5 , APRIL 1962
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be increased further by addition of butanol, permitting the detection of aluminum at a concentration of 10 p.p.m. Pungor and Thege (94)studied the effects of sulfate and ethyl alcohol on emission by cobalt and nickel; sulfate depressed the emission while ethyl alcohol enhanced it. Dean and Stubblefield (25) examined in detail the trvo sensitive lines of silver a t 328 and 338 mp in oxyacetylene and oxyhydrogen flames. The variables considered were burner height, gas flows, organic solvents, and the effects of several cations and anions. llalinorvski, Dancewicz, and Szymczak (68) outline the determination of gallium, indium, and thallium b y flame photometry. Scandium, yttrium. and the rare earths have been studied by a number of groups. Rains, House, and Xenis (100) extract the elements into an organic solvent Ivhich is aspirated into an oxyhydrogen flame. Tables of emission spectra are given for these elements. Bands were found for lanthanum, yttrium. and neodymium which are free from interference by the other elements in this group, a band of europium a t 459 mp is coincident only with bands of terbium and samarium, and only europium and neodymium interfere with the determination of samarium at 6.52 mp. Patrovsky (80) determined scandium, yttrium, erbium, and ytterbium by flame photometry, and Ruf (106) was able to analyze rare earth mixtures for europium. Carnes and Dean (16) studied the emission of yttrium in an oxy-acetylene flame, using a n organic solvent. The effects of gas flo~vand of many anions and cations are described. INDIRECT METHODS
Indirect methods of analysis have often been used for elements Fvhich do not have useful emission spectra in the flame. Several papers have appeared describing new or modified techniques. Poluektov and Kononenko (82) determined boron, chromium, germanium, zirconium, hafnium. molybdenum, vanadium, aluminum, or phosphate by their effect of depressing the rmission of calcium and strontium in the flame. Alalinomki, Rutkon ski, and Szgmczak (69) determined selenium, tellurium, and titnnium by their depression of calcium emission, n-hich is ascribed to the formation of CaSe03, CaH4Ti06. CaTe04. or CaTiF6. Srlenium and titanium were found not to affect the emission of strontium. Robinson (109) describes a method for the indirect determination of sulfate by the addition of an excess of barium and measurement of barium in the supernatant after precipitation. Shaw (113) gives a similar method for sulfate, which was also determined by Odler (78). Bernhart, Chess, and Roy ( 9 )
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ANALYTICAL CHEMISTRY
determined phosphate by its effect on strontium emission. INTERFERENCE PHENOMENA
The study of interference phenomena has continued to be an active area of research. hlalinowski (67) has given a general discussion of interferences. which he divides into physical and chemical effects. Physical interferences arise from the properties of the instrument and the solutions. Chemical interferences are divided into two groupsthose caused by formation of compounds in the flame and those due to changes in ionization equilibria Ionization equilibria have been studied in detail. Hofmann, Kohn, and Schneider (54) have made microwave measurements of electron concentrations in the flame in the presence of cesium and potassium. Ionization n as found to be thermally equilibrated. The mutual influence of the alkali clements due to ionization disturbances was studied by Fukushima (42) and by Borovik-Romanova (11). The effects of easily ionized additives on the emission intensities of calcium, strontium, barium, cesium. and rubidium are described by Lyutyr and Bugrim (65). Poluektov and Yitkun (89) have studied the increased radiation intensity of some elements due to repression of ionization. To correct for background in flame photometry. Dobos (27) makes a series of measurements a t increasing slit widths. The data are cvtrapolated to zero slit width to obtain a measure of line intensity above background. Poluektov and coworkers (85,86, 88) used a dual-atomizer burner to study the cause of some anion interferences. The reduction of the emission intensity of some alkaline earths in the presence of zirconium, uranium. molybdenum, vanadium, or titanium is ascribed to the formation of compounds such as calcium zirconate. Poluektov and Ovchar (85\ report that the emission intensities of some of the rare earths are lower for the nitrates, sulfates. or phosphates than for the chloridcs; this was rclated to the volatilities of the compounds formed in the flame. Baker and Carton (8) studied the effect of phosphate on calcium and strontium emission intensities with a flamc photometer and an atomic absorption spwtrometer. LyutyI and Rossikhin (66) give formulas for calculating partial pressures of elements in the flame in the presence of various additives. It has been found possible to reduce or eliminate some anion interferences by adding releasing agents to the samples to prevent the formation of refractory compounds. K r s t and Cooke (126) found (ethylenedinitri1o)tetraacetate (EDTA) to be an effective releasing agent for the determination of calcium
or magnesium in the presence of phosphate or sulfate. Dinnin (26) found strontium and some of the rare earths to be useful for the same purpose. T’ainshtein and Lebedev (121, 113) showed that acetylacetone or 8-quinolinol can be used to eliminate the effect of aluminum on calcium emission. Killianis (127) employed lanthanum to prevent anion interferences in the determination of calcium in soils. Uulewicz. Phillips, and Sugden (15) measured the stability of metal halides in the flame, and obtained data in good agreement with previous work. Factors which influence sample flon- rate in atomizers were investigated by Winefordner and Latz (IZZS), while Pungor and Hangos (92) studied the effect of solution viscosity on atomization. Pungor, K e s z p r h y , and IiovBcs (95) obtained a kinetic equation for the recpmbination of nrrosol particles in a spray chamlier. ORGANIC SOLVENTS AND EXTRACTION PROCEDURES
The use of organic solvents in flame photometry has received considerable attention. Dvokik (SO) has reviewed the influence of organic compounds in flame photometric analysis. A m i and rllkemade ( 7 ) ascribe the increase of emission intensity caused by an organic solvent to changes in atomization, with changes of flame temperature being of lesser importance. Dean and Carnes (24) found that the droplet size in the aerosol is smaller with organic solvents than when water is used, and related this to observed intensity changes. Pungor and Thege (92)ascribed emission intensity enhancement due to organic solvents to increased rate of evaporation of the droplets, and Robinson (104) related the enhancement to increased atomic concentrations in the flame, rather than to temperature changes. Pungor, Weszprkmy, and PBlyi (96) found that sodium emission decreased when sodium and a n alcohol were sprayed into the flame separately through dual atomizers. indicating that changes in flame temperature cannot account for the enhancements observed Then sodium is introduced in the organic solvent. Neeb (77) has also investigated the effect of organic solvents on emission intensity in the flame. Konopicky and Schmidt (BO) observed enhanced emission for 21 elements when 470 butanol was added to the solutions. Buell ( 1 4 ) and van Rysselberge and Leysen (107) describe methods for the flame photometric determination of lead in gasoline. This is a case where the sample itself provides the benefits of an organic solvent. Several nen- analytical techniques have been based on extraction of the analgte into an organic solvent which is
then aspirated directly into the flame. Goto and Sudo (49) report studies of this method, which they have applied to the determination of calcium (47)) manganese and copper ( i s ) , and iron (46). Extraction into an organic solvent has been used by Knox (69)for the dettmiination of magnesium, and by Menis and Rains (76) for iron. Schoffniann and llalissa (110) describe the simultaneous determination of iron, cobalt, copppr, nickel, and vanadium by organic solvent extraction, while Eshelman and Dean (32) hsvc used such a method for tlie determination of nickel in sheet brass and steel. Thallium in urine was determined n-ith an extraction procedure b y Stavinolia and S a s h (116), and Stander (116) analyzed a variety of materials for vanadium by liquid-liquid extraction into an organic solrent. BIOLOGICAL MATERIALS
Bott (12) and Ames and Kesbett (4) employed specially designed flame photometers to determine sodium and potassium in 0.2- to 2-pl. samples of biological fluids. T h e use of three deproteinizing reagents in the determination of potassium in blood serum was studied by Cobe de Celis, hfartin, and Pacheco (18). Procedures for the determination of magnesium in biological materials wcre described by Famcett and Wynn ( W ) ,Montgomery (76), and Alcock, MacIntyre, and Radde ( 2 ) . Werner (124) added isopropanol to the solutions for the determination of magnesium, and found that the results compared well with gravimetric determinations and with the Titan yellow method. Scharrer and Heilenz (108) employed an ion exchange separation for the determination of strontium in plant materials. Schmid and Zipf (109) n-ere able to determine both strontium and calcium in blood serum by flame photometry. Kick (58) employed flame photometry t o analyze agricultural matrrials for cesium and rubidium. Anderson and Weinbren (6) determined chromium and calcium in feces with a flame spectrophotometer, METALS A N D ALLOYS
Dean (80) has reviewed the application of flame photometry to metallurgical analysis, with emphasis on organic solvent extraction procedures. Ramirez-Nuiioz (101) has also reviewed the>use of flame photometry in this field. Pungor and Zapp (98) employed flame photometry to demonstrate that blisters in aluminum sheet are associated with a high potassium content of the metal in the neighborhood of the blisters. A flame photometric procedure for the determination of as little as O.O1iyo lanthanum in steels was developed by
Goto, Ikeda, and Sudo (46, 119). Additional methods for flame photometric analysis of metals and alloys are cited in the section on Organic Solvents and Extraction Procedures.
spectra in the flame. Gunther, Blinn, and Ott (61) detected organic halogen compounds emerging from a gas chromatograph by means of the Beilstein flame test.
MINERALS
LITERATURE CITED
1-ainshtein and Lebeder (122) have redetermined the lithium, sodium, potassium, rubidium, cesium. calcium, and strontium contents of U. S. Geological Survey Standard G-1 granite and Standard IT-1 diabase by flame photometry, and a new determination of the strontium content of these rock samples n-as made b>- Fornaseri and Grandi (40, 41). Rubinshtein et al. (106) employed an ammonia-oxygen flame to analyze minerals for sodium and potassium. Fabrikova (35) describes a procdure for the determination of rubidium in silicatps, and Fabrikova (36) and Lebedev ( 6 2 ) h a r e analyzed minerals for cesium. Schrenk, Graber, and Johnson (1111 employed an ion exchange separation for the flame photometric determination of copper in mineral mixes. Ford (39) n a s able to determine magnesium. manganese. sodium, and potassium in a single solution of a cement sample n i t h good accuracy and precision in much less time than by standard procedures. MISCELLANEOUS
Factors affecting precision in flame photometry w r e studied by K e s t (166) and b y Dobos and Till (28, 29) Grimaldi (60) outlines a standard additions procedure to compensate for matrix effects in flame photometry. The application of the method of standard additions to the flame photometric determination of the alkaline elements was studied by Stepin and Plyushchev (117 ) , and Beukelman and Lord (10) give a mathematical treatment of the accuracy of this method of standardization. Lebedev and Vainshteh (63) have investigated methods of increasing the sensitivity of detection by flame photometry. There have been several unusual applications of flame photometry. Lengyel, Dobos, and Till (64) measured the rate of dissolution of glasses through determination of lithium, sodium, potassium, calcium, strontium, and barium n-ith a sensitive flame photometer, Lithium was used as a tracer to study the f l o ~of water and sewage by Agg, Mitchell, and Mitchell (1). Magnesium was determined in atmospheric precipitates b y Turkin and Svistov (120), using the method of standard additions. Anderson (5) revierTed the use of flame photomctry to analyze water-formed deposits for a number of elements. Indirect methods can be employed for several anions and for many other elements which do not have useful emission
(1) Agg, A . R.,Mitchell, S . T., lbtchell, ti. L., Iicst. Seuuge €’urij”., J . Proc. 1961,240-5; C. A . 55,251100,(1961). ( 2 ) Al,cock, K., LIacIntyre, I., Radde, I., J . Cl~n.P ~ t h o l 13, . 506-10 (1960). (3) American Society for Testing and Materials, “Methods for Emission Spectrochemical Analysis,” 3rd ed., Philadelohia. 1960. ( 4 ) -4&es, ’Al 111, Sesbett, F. B., Anal. Bzochem. 1, 1-7 (1960). (5) Anderson, C . I I . , i l / i ~ . Soc. Testing _1Iuteiiuls, Spec. Tech. f’ubl. -Yo. 269, 227-43 (1960). ( 6 ) Anderson, J., \‘ieinhreii, I., Clitz. Chinz. Acta 6 , 648-51 (1961I . ( 7 ) Avni, K., Alliemade, C . T. J., Slzkrochim. Actu 196C, 460-71. (6) Baker, C. A,,Garton, F. IT. J., At. Energy Research h t : l k J . ((it. brit.), Kept. AERE-R-3490, 12 pp. (1961). ( 9 j U e r r i h r t , I).S..Chess, K . B D., -4XAL. CHE.\I. 33, 3395-6: (1961 (10) Ueulielman, T. E., Lord, 6. S., -4ppl. Spectroscopy 14, 12--1i (1960). (11) Uorovik-Hornanow, T., Zhrar. .-l/ia/. f h n i . 16, 664-9 (1961). (12) Bott, P. A , , A n d . Biocher,i. 1, 17-22 (1960). (13) Britske, hl. E., Spekti. d n u i i z . t’ Y’svetrmi M e t . (lloscow: Gosudarst. Sauch.-Tekh. Iadatel. Lit. Chernoi i TsvetnoI Met.) Sbornik 1960, 10-IT; C . A. 5 5 , 2 0 5 2 7 e (1961j. (14) Buell, B. E., An2. Soc. Testing dfaterials, Spec. Tech. Ptabl. S o . 269, 157-65 (1960). (15) Bulewicz, E. U.,Phillips, L. F., Yugden, T. &I., Trans. Faruday Soc. 57,921-31 (1961). (16) Carnes, W. J., Dean, J. h., A K ~ ~ I . . CHERI. 33, 1961-2 (1‘361). (17) Clark, G. L., $., “The Encyclopedia of Spectroscopy, Reinhold, New l-ork, 1960.
(16) Cobe de Celis, XI. E., Martin, A,, Pacheco, B., Rev. usoc. bioquim. urg. 25, XO. 129-30, (35-102 (1960); C. A . 55, 23655e (1961). (19) Davis, H. &I., Fox, G. P., Webb, R. J., Wildy> P. C., At. Energy Research Estab. (Gt. Brit.) C/R 2659, 1-35 (1960). (20) Dean, J. A,, Snal3st 8 5 , 621-9 (1960). (21) Dean, J. A., “Flame Photometry,” hIcGraw-Hill, Xelr York, 1960. ( 2 2 ) Dean, J. A,, Record C h e w Piog. 2 2 , 1’79-86 (1961). (23) Dean, J. A,, Burger, J. C., Rains, T. C., Zit,tel, H. E., ASAL. CHICM. 33, 1722-6 (1961). (24) Dean, J. A , , Carnes, 11’. J., Ibid., 34, 192-3 11962’)). ( 2 5 ) ’Dean, ‘J. Stubblefield, C. B., Ibzd., 33,382-6 (1961). (26) Dinnin, J. I., Zbzd., 32, 14T5-80 (1960). ( 2 7 ) Dobos, S.,Acta Chim. .-lead. Sci. Hung. 28, 117-24 (1961). (28) Dobos, S., Till, F., Alagyar K i m . Folyo’zrat 66, 526 (1960). (29) Ibzd., 67, 183 (10613. (30) DvoiAk, J., Cheni lzsty 54, 26-33 (1960). ( 3 1 1 Dvofbh, J , C‘heni. p r f i m s y l 11, 122-6 (1961). ( 3 2 ) Eshelman, H. C., Dean, J. A, ASAL. CHEU.33, 1339-42 (1961). ( 3 3 ) Exley, D., (to Xational Research VOL. 34,
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APRIL 1962
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Development Corp.), Brit. Patent 856,442 (Dee. 14, 1960). (34) Fabrikova, E. A., Spektr. Analiz ZJ Tsvetnoi Met. (Mascon-: Gosudarst. Izdatel. Lit. ChernoI i TsvetnoI Met.) Sbornik 1960, 43-5; C . A . 55, 268409 (1961). (35) Fahrikova, E. -I Zhur. ., Anal. Khlm. 15,427-30 (1960). (36) Ibzd., 16, 22-4 (1961). (37) Fawcett, J. K., Wynn, V., J . Clzn. Pathol. 14, 403-9 (1961). (38) Fischer, J., Kropp, R., Glastech. Ber. 33,380-7 (1960). (39) Ford, C. L., ASTM Bull. No. 250, 25-9 (1960). (40) Fornaseri, ll,, Grandi, L., Geochzm. et Cosnzochzm. Acta 19, 218-21 (1960). (41) Fornaseri, AI., Grandi, L., Metalluiyza zlal. 53, 243-6 (1961). (42) Fukushima, S., 31zkrochzm. Bcta 1960, 332-43. (43) Gilbert, P. T., Jr., Am. Soc. Testzng Materzals, Spec. Tech. Publ. KO.269, 73-156 (1960). (44) Gilbert, P. T., Jr., “Flame Spectra of the Elements,” 2nd ed., Bull. 753-A, Beckman Instruments, Inc., Fullerton, Calif., 1961. (45) Goto, H., Ikeda, S., Sudo, E., S z p p o n Kayaku Zasshz 81, 80-3 (1960); C. A . 54, 13972i (1960). (46) Goto, H., Sudo, E., Bunseki Kagaku 9, 213-15 (1960); C. A . 56, 925g (1962). (47) Ibzd., 10, 171-4 (1961); C. A . 55, 23174g (1961). (48) Ibzd., pp. 175-81; C. A . 55, 23174 (1961). (49) Goto, H., Sudo, E., Sci. Repts. Research Inst. Tohoku Univ., Ser. A .
13,284-98 (1961). (50) Grunaldi, F. S., II. S.Geol. Survey, Prqfess. Papers S o . 400-B, 225 (1960). (51) Gunther, F. A., Blinn, R. C., Ott, L). E., ANAL. CHEK 34,302 (1962). (52) Herrmann, R., Alkemade, C. T. J., “Flammenphotometrie,” 2nd. ed., Springer-Verlag, Berlin, 1960. (53) Hinde, A, U. I
