(163) Zbid., 413. (164) Sill, C! W., Williams, R. L., ANAL. CAEM.,41, 1624 (1969). (165) Simon, H Rauschenbach, P., Znt. J . Appl. Rad&. Zsotop., 20, 725 725 (1969); (166) Skakun N . A,, Kharkov, 0. N., A t . Energ. (USSR), 27, 351 (1969). (167) “Standard Methods for the Exami-
nation of Waste and Waste Water,” 13th Ed, American Public Health Association, New York, N.Y., 1971. (168) State us. Stout. Case No. 31925, Missouri Circuit Court, Cass County, June 29,1970. (169) Symposium on Activation Anal sis in Medicine, Trans. Amer. Nucl.
14,101 (1971). (170) Symposium on
de.,
the Impact of Natural Sciences on Archaeology, London, England, 1969, CONF-691207. (171) Symposium on the Use of Low
Energy Accelerators, London, England, 1970 CONF-700563. (172) ‘hang, C. W., Maletskos, C. J., Science, 167,52 (1970). (173) Trombka, J. I., Senftle, F., Schmadebeck, R., Nucl. Znstrum. Methods, 87,37 (1970). (174) Toe1 wsy, J., Dillinger, P., Pruzienc, J.,?arga, S., Radioanal. Leu., 4, 231 (1970). (175) Toelgyessy, J., Varga, S., Talanta, 17,659 (1970). (176) Toelgyessy, J., Varga, S., Jesenak, V., Lukac, P., Dillinger, P., Radiochem. Radioanal. Lett., 5 , 331 (1970). (177) “Uses of Activation Analysis in Studies of Mineral Element Metabolism
in Man,” Panel Meeting Teheran, Iran. International Atomic Anergy Agency, Vienna, Austria 1970. (178) Velazquez, b., Castrillon, J., Radiochem. Radioanal. Lett., 5 , 243 (1970).
(179) Veres, A., Pavlicsek, I., Radioanal. Chem., 3 , 25 (1969). (180) Verfaillie, G., Euro-Spectra, 8 , 106 (1969). (181) Wa oner, J. A,, Znt. Set. Monogr. Anal. C g m . , 35, 165 (1970). (182) Wakat, M. A., “Catalog of Gamma Rays Emitted by Radionuclides,” Nuclear Data Tables, Sec. A, 8, Nos. 5-6, 445 (1971). (183) Wallace, R. A., Fulkerson, W.,
Shults, W. D., Lyon, W. S., “Mercury in the Environment. The Human Element ” U S . A t . Energy Comm., Rep., ORdL NSF-EP-1 (1971). (184) Wang, Y., Ed.,,, “Handbook of Radioactive Nuclides Chemical Rubber Co., Cleveland, Ohio, 1969. (185) Zeman, A., Stary, J., Kratzer, K.,
Radiochem. Radioanal. Lett., 4, 1 (1970). (186) Zoller, W. H., Gordon, G. E., ANAL. CHEM.,42, 257 (1970).
Organic Elemental Analysis T. S. Ma, Department of Chemistry, City University of New York, Brooklyn, N. Y. 7 12 IO Milton Gutterson, Flavor Applications laboratory, Dragoco Inc., Gordon Drive, Totowa, N .1. 075 12
T
HIS REVIEW SURVEYS recent d e velopments in quantitative analysis of the elements in organic compounds. It follows the previous review (119) and covers the information and publications which came to the attention of writers during the period from October 1969 to October 1971. After vigorous promotion of automatic CHN analyzers by several manufacturers for about a decade (118), two commercial machines are now entrenched in this country. It is of interest to note that foreign instruments have not penetrated the American market and that American manufacturers are not planning to develop automatic analyzers for the other elements. The users of commercial automatic analyzers still make remarks on their “down time,” which necessitates a stand-by instrument in case of emergency. Research publications that appeared in the past two years seem to concentrate on simultaneous determination of several elements with one weighing, organometallic compounds, and the elements with which it is difficult to get accurate results such as oxygen and fluorine. Automated procedures continue to receive attention. This also accounts for the voluminous literature on electroanalytical and other physicochemical methods of finish, since they are amenable to automation.
CARBON AND HYDROGEN
With the emphasis on automated, rapid procedures, a number of papers
have appeared dealing with this topic. Gel’man (76) analyzed various types of compounds by “wide tube” automatic, dynamic combustion. Sels and Demoen (190) have given details of the mechanical and electrical modifications necessary to convert the Coleman Model 33 Analyzer for the determination of C and H. The same authors (191) later modified their method for use with this instrument t o eliminate systematic errors and to reduce the work of the analyst. Stainless steel absorption tubes were used to ensure rapid temperature equilibration and an automated system for connection and disconnection of the absorption tubes and transfer to the balance was developed. Merz (133) reduced the time for analysis to 8 minutes by passing the combustion gases through a cold trap to freeze out the water and then absorbing the carbon dioxide in alkaline solution. This solution was titrated automatically in a nonaqueous system and the volume of titrant was displayed digitally and printed out. In a separate cell, the water was converted to carbon dioxide and titrated as above. The main disadvantages of the ClercSimon method have been overcome (164) and a more accurate determination of the water content of the combustion gas was obtained by collecting a known volume of the gas a t supraatmospheric pressure instead of in an evacuated apparatus. Bailey and Brown (9) recommended covering the aluminum capsules used with the Perkin-Elmer CHN Analyzer with plat-
inum gauze to avoid damage to the combustion tube. Trutnovsky (223) improved the Heraeus micro combustion apparatus by replacing the power relays in the original circuit with triacs. These relays were short-lived and produced noise when switching. Oda, Ono, and Matsumori (162) modified their double tube system for sample decomposition to allow for a more compact apparatus. Either a conventional or gas chromatographic finish was employed. For carbon dioxide, a spectrophotometric’finish could also be used which involved passing the effluent gas through alkaline alizarin yellow GG and measuring the extinction a t 450 nm. While automated procedures received a great deal of interest, studies continued to be made on the nature of the combustion process and the effect of various tube fillings. Buis and Schroder (24) have shown that it is possible t o obtain correct hydrogen values when using an external absorbent for removal of nitrogen oxides, provided that the whole anhydrone filling of the waterabsorption tube was heated a t 8090 “C. Fildes (63) discussed the role of a wide range of fillings and recommended tungstic oxide, silver tungstate, and permanganate as absorptive and oxidative aids for certain refractory compounds. Pechanac and Horacek (162) studied the catalytic efficiency of cobalt(I1, 111) oxide obtained by thermal decomposition of cobalt(I1) oxalate, Methods for the preparation of both the powdered and solid catalyst were given.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
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A number of procedures have a p peared for certain types or classes of organic compounds. Pechanec (161) showed that the formation of nitrogen dioxide during the catalytic oxidation of nitrogen-containing compounds d e pended upon several factors, chief of which are nature of the catalyst, e.g., oxides of manganese, iron, cobalt, or copper give better conversion than silver or platinum; type of compound; temperature; and dimensions of catalyst layer. Klimova and Dubinskii (106) employed a flash combustion technique for aromatic nitro compounds and determined the amount of nitrogen oxides formed. Bazalitskaya (11) determined C and H in organic selenium compounds by igniting the sample in the presence of copper(I1) oxide and magnesium oxide which were also used as the tube filling. The selenium was bound as MgPSe and Cu,Se. For triterpenoids, Gawargious and Farag (73) proposed modifications to three existing combustion methods, In the Vecera method, the c0304 catalyst was activated with nickel oxide and in the method of Korshun and Klimova two silica spirals were introduced into the combustion chamber. In the rapid method of Belcher and Ingram, it was recommended that the sample be covered with powdered co301. For organometallic compounds, Gel'man and Anashina (76) used lead oxide in the combustion zone to ensure complete conversion of the carbon into COZ. For samples containing selenium and a halogen, Shakhova, Zavlokina, and Shish (19.2) pyrolyzed the sample, oxidized the products a t 950 "C over platinum, passed the combustion gases through a layer of heated pumice coated with silver (to remove selenium and halogens) and finally through a Pregl train for absorption of HPO, oxides of nitrogen, and COP. Berezkin, Luskina, Syavtsillo, and Terent'ev, (20) employed a gas chrcmatographic finish for C and H. Combustion took place in a sealed ampoule containing copper(I1) oxide a t 650700 "C. The water content was determined on one column packed with PTFE supporting 10% polyoxyethylene glycol 1540, while the COZwas separated on a second column filled with activated carbon. Campiglio (28) used volumetric titration for both elements. The CO, produced by the combustion was absorbed in dimethylformamideethanolamine and titrated automatically with 0.02N tetrabutylammonium hydroxide in toluene-methanol using thymolphthalein as indicator. The water vapor was adsorbed onto calcium chloride which was subsequently heated and the water absorbed into dimethylformamide containing 1 , l'-carbonyldiimidazole. For each mole of water, 446R
one mole of carbon dioxide was produced which was titrated as above. For the determination of hydrogen only in organic compounds, Jurecek, Cervinka, and Cejka (99) decomposed the sample by mixing with magnesium powder and heating in a stream of argon. The hydrogen produced was converted into water vapor by passage over CuO a t 700 "C, the water was absorbed in Mg(C10&, and weighed. Anisimova and Klimova (4)developed a simple and reliable coulometric cell for determining this element. Chumachenko and Levina (4g) modified their combination gas chromatographic and coulometric method for C, H I and N to the determination of hydrogen only. Wexler (245) employed a spectrometric procedure for the determination of the carbon-linked proton content of alkylated aromatic and unsaturated compounds. Childs and Henner (36) compared the Pregl, Dumas, Perkin-Elmer, and Hewlett-Packard (F & M) procedures for determining carbon-hydrogen and nitrogen. The data indicate that the classical Pregl and Dumas procedures, although slower, gave the most reliable results followed by the Perkin-Elmer and the Hewlett-Packard in that order. Acceptable results can be obtained with any of the four procedures. Several papers have been published concerned with the determination of the radioactive elements. Lloyd-Jones (116) employed flask combustion and precipitated the carbon as CaC03. The dried precipitate was weighed, mixed with Cab-0-Si1 and conventional phosphor solution, and the suspension was transferred to a scintillation counter. Ford (64) decomposed the sample containing carbon-14 in a Parr peroxide bomb with Naz02-KC104 and subsequently analyzed for 14C content by liquid scintillation counting. For the same element, Watson and Williams (243) combusted the sample in the presence of K1O3-KzCr207, fuming HP SO4-HaP04and W02was absorbed in ethanolamine and determined by liquid scintillation counting. For tritium, Barakat and Zahran (10) converted the sample into COz and aHzOand the 3H20 was reduced to a H by passage over hot iron. The tritium was swept out with argon, mixed with butanebutene and passed into a flow-measuring system and counted. Fenton, Mackey, and Creedon (62) combusted the sample and absorbed the products in liquid nitrogen. The latter was then shaken with a solvent to absorb the radioactive material (tritium), which was subsequently counted in standard toluene scintillator solution. NITROGEN
Rapid combustion procedures, with the emphasis on automatic techniques,
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
continued to draw the greatest interest. Dindorf and Hoecker (@) burnt the sample a t 1100 "C in oxygen, swept the products of combustion over cobalt oxide and then over copper metal in a stream of carbon dioxide, and measured the nitrogen produced in a nitrometer. Gautheret, Kubiak, and Nicco (72) used a modified HewlettPackard CHN analyzer to decompose the sample. COZ and nitrogen were separated on a copper column containing Polypak a t 100 OC while a mixture of paraffin wax and dimethyldecylamine was used to obtain the calibration graph for nitrogen content (rectilinear for 0.01 to 0.50% N). Thuerauf and Assenmacher (218) rapidly combusted the sample in pure oxygen a t 800-1000 "C. The combustion gases were swept with helium over copper oxide, then copper, and through 50% potassium hydroxide solution. The gases, now containing only nitrogen and helium, were passed through one arm of a thermistor bridge with pure helium as reference. The amplified signal voltage was applied to a recorder or to an electronic integrator with print out. One determination took four minutes. Leaton (114) analyzed pharmaceutical preparations for nitrogen content using the Coleman Nitrogen Analyzer'Mode1 29A. The method was a combustion process with activated copper oxide-platinum as catalyst and the nitrogen gas was measured volumetrically. Merz (136) developed a new, automatic unit consisting of a vertical quartz tube for combustion in oxygen a t 850 "C, a series of tubes packed, respectively, with copper oxide a t 750 "C, silver wool at 600 "C, and copper a t 500 "C. The nitrogen gas was swept into an automatic print out nitrometer by a stream of COZ. All operations were controlled to a set program. In a patented procedure (201), the sample was combusted and the gases were passed over a catalyst (nickel on magnesium oxide) in a stream of humidified hydrogen to produce ammonia gas, which was then titrated automatically in a micro-titration cell with hydrogen ion generated coulometrically. iiwad and Hassan ('7) studied the fate of nitrogen in various compounds after combustion by a closed flask technique and by reaction in a stream of oxygen with cobalt oxide as catalyst. The amount of nitrogen present as nitrate in the combustion products was considerably increased by the latter met hod. Wet combustion procedures such as the Kjeldahl technique were also of considerable interest. Cedergren and Johansson (SO) digested the samples by the normal technique using HzSO4K2S04 and HgO as catalyst. The acid residue was diluted with a reagent consisting of KBr-NaB407 and the NH3
was then determined coulometrically with a platinum-foil indicator electrode, with the BrO- produced from the bromine generated a t the anode. Davidson, Mathieson, and Boyne (46) reported their experience with an automatic digestion unit. Since in some cases low recoveries were obtained, they recommended manual digestion followed by determination of the ammonia by the indophenol method in the AutoAnalyzer with final calculation by computer. A precision of better than 1% was achieved and a hundred samples per day could be handled. Urban (229) modified a conventional procedure by using p-hydroxybenzoic acid in place of boric acid as absorbent for ammonia. Ashraf, Siddiqui, and Bhatty (6) determined the ammonia by an indirect precedure. T o the digestion flask was added a standard solution of KBr08-KBr, the solution was made alkaline, and the excess reagent was determined iodimetrically. A blank had to be run. Fedoseev and Osadchii (61) proposed a diffusional displacement technique for the liberation of the ammonia after mineralization of the sample. Alkali-impregnated filter paper was placed on the surface of the solution of the ammonium salt, while filter-paper impregnated with 0.01N acid solution was placed 3-5 mm above the surface to absorb the ammonia. The excess of acid was titrated in the same apparatus. Apparatus for carrying out Kjeldakl digestions have been described. Reardon (171) digested the samples in an insulated test-tube rack on a hot-plate. Faithfull (69) used an aluminum block placed on top of a hot plate, insulated with asbestos board. The samples were placed in test tubes which fit into holes drilled into the block. A p proximately 150 digestions could be carried out per day. Strauch (206) used an electrically heated aluminum block with holes to accommodate 30 tubes of approximately 50-mm diameter. Morris, Carson, and Jopkiewicz (141) compared the automated Dumas method for nitrogen in fertilizers to the official A.O.A.C. Kjeldahl method. The Kjeldah1 method was more precise and more determinations per hour could be performed. However, costs and space requirements were less for the Dumas method. Stitcher, Jolliff, and Hill (203) found that the automated Coleman Nitrogen analyzer gave results in close agreement with those given by the Kjeldahl method. The automated Dumas method gave rather higher recovery of nitrogen than the Kjeldahl method. Zelenina and Shemayakin (263) determined total nitrogen in polyamides by mercurimetric titration.
OXYGEN
A number of modifications and improvements in the direct determination of oxygen have appeared. Stefanac, Sliepcevic, and Rakovic-Tresic (202) minimized blanks in the Unterzaucher method by excluding the permanent carbon packing of the pyrolysis tube. Instead the sample was covered with carbon and pyrolyzed by static flask combustion a t 1120 OC in an empty tube. Sliepcevic and Stefanac (199) improved the above described procedure by employing platinized carbon to cover the sample, thus reducing the pyrolysis temperature to 900 "C. The time for a determination was also shortened Belcher, Ingram, and Majer (18) studied the carbon reduction process in the Unterzaucher method and concluded that the process was not completely satisfactory. Mesaric (137) modified the method by using "decomposed" silver permanganate to oxidize CO to COZ and passed the products of pyrolysis over copper a t 900 "C to remove any sulfur. A number of automated procedures have been described. Merz (136) developed an apparatus for the completely automated determination of oxygen in which approximately five determinations per hour could be performed. Calme and Keyser (26) absorbed iodine vapor in an absorption cone and used an automated titration cell to determine the carbon dioxide produced. The time for an analysis was between 11 and 13minutes. For samples containing elements other than carbon, hydrogen, and oxygen, several special techniques have been proposed. For organometallic compounds, Merz (134) pyrolyzed the sample (5 mg) in the presence of hexamine (10 mg), NH&l (20 mg) and AgCl (20 mg). The COZ produced was absorbed in dimethylformamide and titrated with tetrabutylammonium hydroxide. Terent'ev, Volodina, and Besada (213) hydrogenated samples containing C, H, 0, and N in a mixture of nitrogen and hydrogen gases a t 800-900 "C. As catalyst they used either nickel or nickel-thorium oxide, respectively, on pumice. The water produced was determined gravimetrically. For sulfur-containing samples, the same authors (212) absorbed the sulfur-containing gases on a layer of copper a t 350 "C which preceded the hydrogenation catalyst. Also for sulfur-containing samples, Gel'man and Grigor'yan (77) decomposed the sample in a graphite capsule a t 980 "C and absorbed the HzS and CSz produced in two layers of reduced nickel at 600 and 400 "C, respectively. The sulfur-free gases were passed over a platinum black catalyst layer and then over CuO a t 220 "C to convert CO + COz which
was then determined gravimetrically. For organofluorine compounds, Fadeeva (67) pyrolyzed the sample in a closed system over a layer of platinum black at 1000-1100 "C in an atmosphere of nitrogen and absorbed any HF produced with silica gel. The resulting CO was oxidized to COZ by CuO a t 300 "C and the COZ was determined gravimetrically. Gouverneur and Bruijn (81) described a procedure for compounds containing metals, phosphorus, or boron, which included automated non-aqueous titrations of the COS produced. Several procedures have been d e veloped for the determination of the CO produced from the oxygen-containing sample other than the conventional conversion to COZ and gravimetric measurement. Chumachenko and Khabarova (40) pyrolyzed the sample in helium a t 1100 "C over carbon and conveyed the gases produced to a gas chromatographic column of SKT carbon where the CO peak was recorded with a katharometer. Absolute errors for 250 organic substances were *0,2%. Thuerauf and Assenmacher (217 ) determined the CO by a nondispersive I R gas analyzer without separation of other components. Hozumi and and Tamura (96) studied the effect of operating conditions on their method which utilized an automatic recording analyzer in conjunction with an optical integration method for iodine obtained from the reaction of CO with IzOs. Lakomy, Lehar, and Jurecek (112) converted the CO into COZ by passage over CuO a t 600 "C and absorbed the COz in 0.03M NaOH, the conductivity of which was then measured. Results were obtained by reference to a Calibration graph. Nakamura, Nishimura, and Mitsui (144) treated the COz with lithium hydroxide to produce water which was determined in an electrolytic hygrometer. Several radioactive techniques have been described for the determination of oxygen. Keller and Muenzel (103) irradiated the sample with high energy neutrons and measured the positron decay with a methane flow-counter. Since fluctuations in neutron current occur, reference samples were simultaneously irradiated. For fluorinated samples, Olson and Kulver (163) proposed an isotopic-dilution method. The sample was pyrolyzed together with '%-containing succinic acid and the pyrolysis gases were admitted to a mass spectrometer. Comparison of the m/e 46 to 44 ratio (C1601s0to Cleo,) with the ratio obtained from the pyrolysis of the '%-containing succinic acid provided a means of calculating the oxygen content of the sample. Rafaeloff (17 0 ) developed a neutron-activation analysis method based on counting the "F produced after the sample was
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
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irradiated in the presence of lithium compounds. Taylor and Chen (209) determined radioactive oxygen-18 by converting the sample to COZ which was then measured in a mass spectrometer. Variables which affected the conversion and measurement were studied and suggestions were given for ensuring a reproducibility to within =tO.l%, on samples which differed by a maximum of 10% in their contents of '80. HALOGENS
The flask combustion technique for the decomposition of halogen-containing samples has by far received the most attention. Wiele and Horak (246) improved the design of the Schoniger combustion flask. The apparatus, which is suitable for routine analysis, employed electrical ignition. For chlorine in polyvinyl chloride polymers containing inorganic fillers, Truscott (228) used the flask combustion technique followed by atomic absorption spectrometry. Skorobogotova, Faershtein, and Kravchenko (196) mixed the sample with hydrazine sulfate before the combustion for iodinecontaining samples. Potassium hydroxide solution was used as absorbent and the iodide ion was titrated with 0.005N Hg(NO& in ethanol-water (3:1) medium with diphenylcarbazone as indicator. Celon, Volponi, and Bresadola (33) employed 0.15% NaB& in alkaline solution as absorbent and titrated the halide ion liberated from copper-containing organic complexes with 0.01N Hg(C10& using the sulfur analog of Michler's ketone [4,4' bis- (dimethy1amine)thiobenzophenone] as indicator. Results were as precise as those obtained with diphenylcarbazone as indicator in the absence of copper. Celon and Marangoni (32) also used alkaline sodium borohydride solution as abserbent for samples centaining mercury and antimony in addition to chlorine and bromine. The halides were titrated with 0.01N Hg(C104) using diphenylcarbazone as indicator. Pikulikova, Springer, and Kopecka (166) successfully applied the flask combustion technique to the determination of iodine or bromine in various drug samples. The products of combustion were absorbed in alkaline peroxide solution and the halide ions were titrated with standard mercuric nitrate solution. Secor and White (183) used a coulometric technique for the determination of iodine after oxygen-flask combustion. For the determination of the titration constant (mg of halide per sec) either potassium iodate, potassium hydrogen di-iodate, or potassium iodide were satisfactory standards. A number of other decomposition methods in addition to flask combustion
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have been reported for halogen-containing samples. For water soluble compounds containing labile halogen, Egli (66) decomposed the sample with alkaline sodium borohydride solution in the presence of a palladium salt as catalyst. The halide ions were finally titrated potentiometrically using silver nitrate solution. Hadzija (86) pyrolyzed the sample a t 800 OC in a stream of oxygen and absorbed chlorine or bromine externally with lead chromate at 400 OC. Sulfur was also absorbed but iodine was not and nitrogen did not interfere. For halogen in organoiron or -tin compounds, Strukova and Kashiricheva (206) ignited the sample in an oxygen filled bomb with sodium peroxide. The chloride ion was titrated potentiometrically with silver nitrate solution in the presence of EDTA to mask Fe*+ and Sn4+. Drushel (63) employed empty tube combustion before determining the chloride ion by a coulometric technique. Optimum operating conditions for the combustion were specified. Volodina and Gorshkova (237) heated the sample in a stream of gaseous ammonia at 700 OC. The resulting ammonium halide in aqueous solution was passed through a column of KU-2 cationite (H+ form) and the acid in the percolate was titrated with standard alkali solution. Debal and Levy (@) mineralized the sample instantaneously in a stream of moist oxygen inside an "Ingram" Chamber a t lo00 "C, the conditions being such that hydrochloric acid rather than chlorine was formed. The acid was determined automatically by a coulometric technique. Other halogens and sulfur had to be absent. Osadchii and Fedoseev (166) fused the sample with magnesium silicide and determined the liberated halogen in the extract. The technique was also applicable to the determination of nitrogen. Krijgsman, Griepink, Mansveld, and van Oort (107) developed a semi-automated method in which the sample was combusted in a stream of oxygen at 900-1OOO "C over palladium, quartz, and platinum. The combustion gases were absorbed in a solution of hydrazine sulfate and hydrogen peroxide in 80% acetic acid saturated with the appropriate silver halide. The halide ions were titrated automatically with silver nitrate solution during the absorption, with indication of the end point by an ion-specific electrode. Vitalina, Shipula, and Klimova (2%) have shown that organic halogen compounds completely decompose under the light of a xenon lamp. The minimum time of decay was observed for iodo derivatives, the maximum time for fluoro derivatives. Vinson and Fritz (232) liberated halide ions from organic compounds by reaction with a base in dimethyl sulfoxide medium.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
The rate of reaction in this medium was considerably greater than in aqueous or alcoholic media. The liberated halide ion was determined by the Volhard method. Kusaka and Tsuji (108)used a nondestructive technique for the determination of chlorine. The sample was irradiated with neutrons and the emitted gamma rays were measured. Chlorine, among several other elements, gave prominent peaks suitable for high-sensitivity analysis. The error was less than 5%. Because of the difficulties often encountered in the determination of fluorine, this element wl?l be treated separately in this section. Most techniques involved preliminary combustion in an oxygen-filled flask. Van den Bossche, Haemers, and de Moerloose (330) then determined the liberated fluoride ion spectrophotometrically after reaction with the Ce4+ complex of alizarin fluorine blue. The method was applied to drugs and pharmaceutical preparations. Horacek and Pechanec (94) modified their previously published method to eliminate any interference from the presence of phosphorus and arsenic in the sample. After the combustion, cadmium chloride and acetone were added to precipitate the interfering elements and the fluoride was determined as before. Pavel, Kuebler, and Wagner (16'0) determined the fluoride ion by direct measurement with a fluoride-sensitive electrode. After the combustion, potassium hydroxide and buffer solution was used to make up to 50 ml before the measurement. Sodium fluoride was used to prepare standard fluoride solutions. Larina and Gel'man (113) determined the fluoride ion in the absorption solution spectrophotometrically from the decrease in the extinction of the thorium-arsenazo I complex. Any phosphorus present was precipitated with a zinc salt and the determination run on an aliquot of the filtrate. Excess zinc ion did not interfere. Selig (189) used sodium hydroxide solution as absorbent and after elimination of COz by boiling the acidified solution and precipitation of sulfur with a barium salt, the fluoride ion was titrated potentiometrically with 0.02M lanthanum nitrate solution. Phosphorus interfered and must be separated from the fluoride ion by ion exchange or distillation. The same author (187) eliminated the interference of phosphorus by absorption on zinc oxide which did not have to be removed before the potentiometric titration. Cheng (34) improved his previously described titrimetric procedure using 0.01N thorium nitrate solution and arsenazo I as indicator. His improvements involved introduction of a combustion aid to the flask to ensure complete conversion of the fluorine to hydrogen fluoride; employment of a
glycine-perchlorate b d e r for the titration medium; and use of an automatic titrimeter to simplify detection of the end point. Francis, Deonarine, and Persing (67) used lanthanum or thorium nitrate solution in conjunction with a fluoride specific electrode for the determination of the fluoride ion in the absorbing solution. Shearer and Morris (196) combusted the sample in a polypropene flask and determined the fluoride ion by direct measurement with a fluoride sensitive electrode. Sodium fluoride was used to prepare a calibration graph. Volodina, Gorshkova, and Terent'ev (240) decomposed the sample a t 700 OC in a silica tube in a stream of gaseous ammonia to form ammonium fluoride, which was washed out of the tube with water. The washings were titrated with thorium nitrate solution or alternatively passed through a cation-exchange resin and the resulting H F titrated with standard alkali. Schoenfield (181) adapted a direct spectrochemical technique for fluorine based on the emission of CaF bands in a dc arc to the determination of fluorine in organic compounds. Satisfactory results were obtained with various types of compounds, although the fluorine content of those compounds containing boron or silicon could not be measured because of the volatility of BF3 and SiF4. Sulfur, Selenium, Tellurium, Phosphorus, and Arsenic. For sulfur, several procedures which involved closed flask combustion have appeared. Stoffel (804) improved his previously described method in that the final titration was performed by a potentiometric recorder to record changes in extinction a t 489 nm and simultaneously to control a piston buret for delivery of the titrant. Bishara (83) treated the absorbing liquid with excess barium chloride solution and determined the unconsumed Ba2+ polarographically. Selig (186) titrated the sulfate ions potentiometrically with lead perchlorate solution using a PbZ+specific electrode and expanded scale p H meter to follow the titration. Phosphorus had to be removed and fluoride was masked with boric acid. Schuessler (182) designed a special flask for the combustion. After the combustion, the gases were equilibrated in a gas-sample loop and then injected into a gas chromatograph. The relative error was 5y0. MendesBezerra and Uden (132) added ammoniacal EDTA to the absorbing solution to prevent precipitation of the barium sulfate and determined the sulfate ion nephelometrically with 4'-chlorebiphenyl-4-amine. Loginova, Baranova, and Nesterova (117) employed potassium chlorate as the absorbing solution and measured the sulfate ion nephelometrically after the
addition of barium chloride and hydrochloric acid. Campiglio (2'7) titrated the sulfate ion present in the absorbing solution (aqueous hydrogen peroxide) with 0.01N Ba(C104)Z using thoron I as indicator. Gersonde (79) used alkaline peroxide solution as the absorbent and precipitated the sulfate ion with strontium chloride. The precipitate was recovered, dissolved in ammoniacal EDTA, and the strontium determined in a flame spectrophotometer (oxyhydrogen flame) a t 681 nm. Yih and Mowery (262) improved the reproducibility of the end point in the titration of sulfate with barium chloride using tetrahydroxyquinone as indicator by use of a filter photometer with a recorded output. Other combustion techniques for sulfur have been investigated. Do(62) kladalova and Nekovarova modified a method wherein the combustion was performed in an empty silica tube. In their modification, the conditions were such that partial oxidation of SOz to SO3 which caused errors was prevented. Dokladova and Banas (61) studied the empty tube combustion and reported that nitrogen derivatives altered the ratio of SO2 to SO, in the gas phase, while halogen compounds affected the spectrophotometric determinations of the sulfur dioxide as pararosaniline methanesulfonic acid. Drushel (63) specified optimum o p erating conditions for the oxidation of sulfur in the empty tube combustion and determined the sulfur by a coulometric technique. Several pyrolytic methods for decomposing sulfur-containing samples are of interest. Chumachenko and Alekseeva (39) sealed the sample in a tube with hexadecane as a source of atomic hydrogen and pyrolyzed the sample in a stream of argon. The gaseous products were separated by gas chromatography and the hydrogen sulfide issuing from the column was determined conductimetrically by absorption in mercuric nitrate solution. Mlinka and Dobis (139) heated the sample in a stream of hydrogen and passed the gases over l4C-1abeled cadmium carbonate. The W O Pformed was retained in a liquid air trap for counting with a methane gas counter. Volodina, Abdukarimova, and Ter(236) hydrogenated the ent'ev sample a t 950 O C and absorbed the resulting HZS in a solution of zinc acetate, and finally determined the sulfur iodometrically. Wronski and Bald (860) desulfurized the sample by heating in the presence of Raney nickel. The HzS was liberated from the NiS with acid and distilled into sodium hydroxide solution and titrated with o-hydroxymercuribenzoic acid solution, dithiofluorescein being the indicator. Covic and Sateva (44) also described a
method using Raney nickel as reductant for sulfur in propene tetramer samples. The liberated hydrogen sulfide was determined by a titrimetric procedure. Volodina, Abdukarimova, Gorshkova, Borodina, and Zhardetskaya (234) p y r e lyzed the sample in a stream of nitrogen a t 700-750 "C. The resulting SO2 was absorbed in sodium tetrachloromercurate solution and an aliquot was treated with aqueous fuchsine-formaldehyde reagent and the extinction was measured and compared to a calibration graph. The above method was used to determine the sulfur contents of dimethyl sulfoxide and diphenyl sulfoxide (238). Volodina, Abdukarimova, and Kozlovskaya (236) determined both the oxidized and reduced forms of sulfur in organic compounds by a modification of the method described above. For the oxidized form of sulfur, the pyrolysis was performed in the presence of copper powder, than the powder was heated in a stream of air to yield SOZ equivalent to the reduced form of sulfur. Chumachenko and Alekseeva (38) decomposed the sample in a stream of argon a t 1150-1200 "C in a silica chamber and the gaseous products were absorbed in a cell containing cadmium acetate. The sulfur was then determined titrimetrically by an iodometric procedure. Brinkowski and Wronski (12) improved the Burger-Zimmermann method for sulfur in which the sample is decomposed with potassium and then the hydrogen sulfide is distilled off by a laborious technique. In their procedure, the potassium was dissolved, and then the sample solution was titrated directly with o-hydroxymercuribenzoic acid solution. Strukova and Lapshova (207) used bomb fusion with sodium peroxide to decompose the sample. An extract of the melt was subjected to column chromatography and the sulfate ions eluted from the columns were titrated with 0.01M Ba(N0& using 3,6,-bis-(4nitro-2-sulfopheny1azo)chromotropic acid as indicator. The end point was made more reproducible by use of a filter photometer with a recorded output. Wollin (148)decomposed the sample by wet oxidation using a mixture containing bromine and nitric and perchloric acids. The sulfur was precipitated with a barium salt, the precipitate dissolved in the sodium salt of EDTA and the barium determined by atomic absorption spectrophotometry (airacetylene flame; 553.6 mm). Tiwari, Johar, and Trivedi (119)also employed wet oxidation using potassium permanganate and peroxophosphoric acid (formed by the reaction of deactivated Pz06 and hydrogen peroxide). The resulting sulfate ion was determined gravimetrically as the barium salt. For sulfur in fluorocarbon polymers,
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
449R
Heslop and Tay (93) irradiated both the sample and a standard with neutrons to convert some into azP. The samples were ignited by closed flask combustion to convert S, P, and F into HzS04, HaPO4, and HF, respectively, and after adding potassium dihydrogen phosphate as phosphorus carrier to both the sample and standard solutions, part of the phosphorus was precipitated as molybdovanadophosphoric acid which was extracted into isobutyl methyl ketone. A portion of the extract was counted for szP in a Geiger-Mueller liquid counter. M a and Zoellner (110) digested organo-tellurium compounds with a mixture of nitric and sulfuric acids. The Te(1V) was then oxidized to Te(V1) by excess 0.02N potassium dichromate, and the excess was determined spectrophotometrically or by titration with 0.02N ferrous sulfate. For phosphorus, Romer and Griepink (174) studied the losses occurring in a closed flask combustion technique. These losses were avoided by simply putting the platinum gauze in the absorption solution and hydrolyzing in basic and acidic solution. There remained no platinum-phosphorus compounds after this procedure. Selig (188) used closed flask combustion with alkaline bromine solution as absorbent. Excess 0.02N cerium nitrate solution was added and the excess titrated with standard EDTA solution using methylthymol blue or xylenol orange as indicator. For compounds difficult to decompose, Tysganova and Novikova (916)added paraffin wax to the sample before closed flask combustion and then titrated the resulting phosphate with 0.01N La(NOa)a, using Chrome Azurol S as indicator. Shanina, Gel’man, and Bychkova (193) applied a previously described closed flask procedure for phosphorus, in which the phosphorus was determined spectrophotometrically as reduced molybdophosphate, to over 800 compounds containing a great variety of other elements. The error in all cases was *0.3%. Dindorf and Luckenbach (50) reported that in the Carius fusion of certain organophosphorus compounds, the decomposition did not proceed to the phosphate. For example, tertiary phosphine oxides with a methyl group attached to the phosphorus atom, produced methylphosphoric acid. Slanina, Frintrop, Mansveld, and Griepink (198) digested the sample in PTFE tubes with a mixture of perchloric and nitric acids and osmium tetroxide as catalyst. The p H change caused by the reaction 2H20 Laa+ HzPO4- + Lap04 -i2Ha0f was used as the basis of a semiautomated potentiometric titration with lightly buffered lanthanum nitrate solution as titrant. Hayton and Smith (98) oxidized the sample and titrated P(II1)
+
450R
+
with Karl Fischer reagent. Kirpichnikov, Kolyubakina, Minsker, Mukmeneva, and Chebotareva (106) reacted esters of phosphorus acid with cumene hydroperoxide to form the corresponding P(V) acid. The unconsumed reagent was determined polarographically with use of a dropping mercury electrode. For arsenic, Shanina, Gel’man, and Mikhailovskaya (194) employed closed flask combustion with KMn04 in N-HzS04 as absorbent. The arsenic was then determined photometrically at 850 nm as the blue molybdoarsenate complex. Arnold, Davis, and Jordan (6) developed a radioisotope-dilution method for arsenic in which the sample was decomposed by wet oxidation with nitric and sulfuric acids. The - 4 ~ 0 4 ~ was reduced to AsOZ- with iodide solution, radioactive “As labeled solution added, and the mixture extracted with zinc diethyldithiocarbamate solution. Finally this solution was shaken with chloroform and the gamma activity of the organic layer measured. Recoveries of >98% were achieved. Dean and Fues (47) proposed flameemission spectrophotometry for organoarsenic compounds. The sample was burned in an acetylene-oxygen flame and the absorption was measured a t 235 nm and compared to a calibration graph. For difficulty-volatile substances, Griepink, Krygsman, LeenaersSmeets, Slanina, and Cuijpers (84) burnt the sample mixed with poly(methylmethacrylate) and potassium nitrate in an oxygen filled flask. The As048- were titrated potentiometrically with standard lead nitrate solution. ORGANOMETALLICS
For silicon-containing samples, Wetters and Smith (844) improved previously described procedure in which the samples were decomposed by alkali fusion. For siloxane polymers, a pretreatment step with alcoholic alkali was proposed. Terent’ev, Bondarevskaya, and Gradskova (110)fused the sample with sodium peroxide in an oxygen-filled bomb. The melt was dissolved, ( N & ) ~ M ( ~ O Z ~ added and .4H@ the extinction of the molybdosilicic acid compared to a solution containing a known amount of silicon and the reagents. The same authors (111) improved the above procedure by using a solution of K2Cd4 as the color standard, Prey, Teichmann, and Bichler (168) determined silicon directly in a solution of the organic compound by atomic absorption a t 250.6 nm (NzO-acetylene flame). Results were considerably influenced by the solvent used and butyl ether containing a small proportion of hydrochloric acid was the most suitable. Obtemperanskaya, Dudova, and Dikaya (150) burnt germanium-containing sam-
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
ples in an oxygen-filled flask. The GeOz formed was determined spectrophotometrically with phenylfluorone or resarson. For the same metal, Remtova and Chvalovsky (171) also used closed flask combustion and determined the germanium content of the absorption solution polarographically (Ellz = -1.34 V us. the S.C.E.). For aluminum-containing samples, Hagen, Biechler, Leslie, and Jordan (88) employed hydrolysis with concentrated hydrochloric acid and then added excess 0.05M 1 ,Sdiaminocyclohexanetetraacetic acid. The unconsumed complexan was titrated with 0.05M ZnSO4 in the presence of dithizone as indicator. Jordan and Leslie (98) improved the above procedure by eliminating several steps. For aluminum, titanium, or tin in organosilicon compounds, Myshlyaeva and Maksimova (143) employed acid hydrolysis to break the metal linkages and determined the liberated metal by a complexometric technique (EDTA backtitrated with ZnSO4 solution, xylenol as indicator). Kyriakopoulos (110) extracted lead from tetraethyl-lead in gasoline containing manganese additives with KClOa solution in nitric acid. The lead was finally determined gravimetrically as the chromate salt For boron-containing samples, Abramyan, Gevorkyan, and Sarkisyan (1) heated the sample in a sealed glass tube a t 400-500 OC with KMnO4. The tube was washed with dilute nitric acid containing hydrogen peroxide and the boron content determined by titration with sodium hydroxide solution before and after the addition of mannitol. Celon and Bresadola (31) determined boron spectrophotometrically with azomethine H, measuring the extinction a t 415 mm. The sample was mixed with sucrose and sodium peroxide before being decomposed by closed flask combustion. For the determination of boron mixed with polyphenyls, Sefidvash (184) employed infrared spectrophotometry between 1600 and 1200 cm-1 making use of the doublet (1412 cm-1 and 1370 cm-l) associated with the B-0 linkage. For solid organoboron compounds, Selecki and Nowakowska (185) used the technique of indirect neutron activation. The detector, an indium plate, was enveloped in a shield of the boron compound and was irradiated with neutrons. The induced activity of the Il6In was measured using a scintillation counter and the boron content calculated from a logarithmic relationship determined by treating known amounts of B203 in a similar manner. Abramyan and Gevorkyan (1) decomposed mercury-containing samples in a sealed tube a t 400-500 OC with KMn04. The mercury in the nitric acid extract was titrated with 0.01N
KI in the presence of starch solution. For the same element, Busev and Teternikov (26) digested the sample with concentrated H2SO4 (using hydrogen peroxide if necessary) and precipitated the mercury in the digest with excess nickel diethyl phosphore dithioate. The excess reagent was titrated with 4-dimethylaminophenylmercury acetate either potentiometrically or visually with diphenylcarbazone as indicator. Bromide and iodide interfered. Ehrlich-Rogozinsky and Sperling (56) digested the sample with HN03-HC104 and determined mercury amperometrically with bis-(2-hydroxyethy1)dithio-carbamate in isopropyl alcohol. The rotating platinum electrode was maintained a t -0.2 V us. the S.C.E. Terent'eva and Malolina (216) decomposed manganoorganic compounds with sulfuric acid containing hydrogen peroxide and determined the manganese in the residue polarographically ( d r o p ping mercury electrode, -0.5 V us. the S.C.E.). A standard solution of MnCl.4H20 was used for calibration. For lithium in certain metal complexes, Sarry and Grossman (179) employed an indirect titrimetric procedure in the absence of air. Benes and Tomasek (19) investigated several conventional radiochemical methods for the determination of la7Cs in ashed organic material. Two methods were recommended: precipitation of cesium tetraphenylborate; extraction of cesium by dipicrylamine in nitrobenzene a t p H 10, reextracting with N-HNO, and evaporating to dryness. Macdonald and Sirichanya (121) proposed simple and rapid procedures for calcium, magnesium, barium, zinc, manganese, or cobalt in organic compounds which involved closed flask combustion followed by titration with EDTA solution. Organic compounds containing nickel, copper, iron, or bismuth were best decomposed by wet combustion. Simultaneous Determination of Several Elements. The determination of carbon, hydrogen, and another element, especially nitrogen or the halogens, has drawn the most interest. Wachberger, Dirscherl, and Pulver (242) developed an automatic apparatus for the determination of carbon, hydrogen, and nitrogen. The sample was combusted in oxygen and the combustion products were separated in a stream of helium by means of selective adsorption and desorption. The liberated nitrogen, carbon dioxide, and water were determined successively by means of thermal conductivity measurements. Marzadro and MazzeoFarina (126) used an analyzer with C0304-CuO as oxidation catalyst for the same elements and reported results within =!=0.30/, of calculated values. Chumachenko, Pakhomova, and Ivanchikova (43) developed an im-
proved technique for destructive oxidation of organic compounds in a closed system followed by determination of the elements by gas chromatography. The substances were heated a t 900950 "C in a closed oxygen-filled tube. For organosilicon, organoboron, and organophosphorus compounds, it was necessary to include NiO in the closed system. Res1 (173) pyrolyzed the sample with AgMn04 and reduced copper and passed the combustion products diluted with helium into a gas chromatograph with katharometer detection. Two records, of sorption and desorption, were obtained from a single sample for carbon, hydrogen, and nitrogen, thus increasing the accuracy of the determination. Chumachenko and Levina (41) decomposed the sample by heating in the presence of nickel oxide and then determined the liberated COZ and nitrogen by gas chromatography. The HzO was absorbed on P20s in a cell fitted with two platinum wire electrodes and then electrolyzed in a sealed volume of helium. The products of the electrolysis were subsequently passed through the gas chromatograph. The hydrogen content was obtained from the current consumed during the electrolysis and from the peak height recorded in the chromatograph. Dugan and Aluise (64) employed the technique of dynamic flash combustion using oxygen-helium a t 1060-1080 "C in a silica tube without a catalyst to decompose the sample. Products of combustion were retained and separated in two cold traps, one containing Carbowax 20 M on PTFE to retain Con, SO2, and HzO and the other molecular sieve 5A to retain nitrogen. Sequential heating of the traps released the gases which were measured by thermal conductivity. For carbon, hydrogen, and a halogen (chlorine or bromine), Marzadro and Zavattiero (128) burnt the sample a t 750 "C using granular c0304 as catalyst. The halogen was retained in a quartz tube packed with silver sponge, and carbon dioxide and water were absorbed as usual. Hadzija (87) employed lead dioxide as external absorbent for halogens (or SO2 for sulfur). Nitrogen had to be absent. For compounds containing fluorine and other halogens, Rotzsche and Jurczyk (177) combusted the sample by conventional means in a stream of oxygen or nitrogen. The elements were determined gravimetrically by passing the resulting gases successively through silica wool a t 950-1000 "C which converted the fluorine into SiFa; finely-divided silver a t 350-450 "C to absorb C1 or Br; MgO a t 600 "C to absorb the SiF4; and conventional absorption tubes for water and carbon dioxide. Fadeeva and Diakur (58) showed that combustion in a stream of oxygen for organofluorine
compounds and absorption of the fluorine on AlzO, FezOa, or ZnOz in the decomposition zone was only quantitative for ZnOz although the results were unsatisfactory. They also demonstrated that combustion with a platinum catalyst and a layer of finely divided silica produced HF in addition t o SiF, in compounds containing hydrogen. For organic complexes and salts of palladium and praseodymium, Bazalitskaya and L'dokova (12) pyrolyzed the sample at 800-850 "C in a stream of oxygen. The metals were determined by weighing the remainder (either PdO or PrsO,,), while carbon, hydrogen, and halogen were determined by usual methods. Obtemperanskaya and Dudova (149) used a similar technique for C, H, halogen, and germanium. The metal was determined by weighing the residue (GeO2). The same authors (148) alternatively determined the germanium content by dissolving the the oxide in alkaline solution, treating the solution with phenylfluorone and measuring the extinction a t 530 nm. Terent'ev, Volodina, Fursova, and Martynova ($14) combusted organoselenium compounds in a stream of oxygen over a platinum catalyst. The resulting CO,, H20, and SeOL were determined gravimetrically after absorption on Ascarite, anhydrone, and powdered quartz, respectively. For carbon, hydrogen, and sulfur, Obtemperanskaya and Mullayanov (161) burnt the sample in a special cell with a close-fitting lid carrying platinum electrodes for ignition. The cell was kept at 100-110 "C to avoid condensation of water vapor and the infrared spectrum of the products (C02 and H 2 0 with a lithium fluoride prism and SO2 with a sodium chloride prism) was recorded with reference to another cell filled with pure oxygen. For organic compounds containing a multivalent element that forms a volatile oxide (Re, As, Se, or Mo) in addition to carbon and hydrogen, Gel'man, Sheveleva, and Shakhova (78) combusted the sample a t 900-950 "C and carbon and hydrogen were determined gravimetrically by conventional means, while the Re was weighed a t AgReO4 (formed by reaction of Re207 with metallic silver a t 450 "C) and the other elements were determined by weighing their oxides retained in the combustion tube. For the simultaneous determination of halogens present together in organic compounds, Papay and hlazor (158) employed flask combustion to prepare a stock solution of the sample. In one aliquot, chlorine and bromine together were titrated with O.O2N AgNOa in the presence of Variamine blue as indicator. I n another aliquot, NaC103 was added and the bromine alone determined iodimetrically. For the same
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
451R
elements, Bigois, Levy, and Marlain (91) titrated Br- (after combustion of the sample) with 0.002N AgNO, using as indicator electrode polished silver that had been equilibrated with an aqueous suspension of AgBr until the changes in potential produced by known concentrations of Br- and C1- agreed with calculated values. Total halogen was determined by a similar titration of a separate aliquot using an indicator electrode equilibrated with an aqueous suspension of AgC1. Gawargious, Habashy, and Faltaoos (74)subjected the sample solution after combustion to polarography for bromine and iodine. Waves a t E112 = -1.35 to -1.4 V and E112 = -1.8 to -1.85 V were recorded corresponding to 10s- and BrOs-, respectively. For chlorine and iodine, the solution was polarographed at -0.1 V vs. a mercurous sulfate electrode for chlorine and then in a separate aliquot, I- was oxidized by bromine solution and determined with the same electrode system a t a starting potential of -1.35 V. Volodina, Ivin, and Pal'yanova (241) employed a reduction method for chlorine and bromine in organophosphorus compounds. The sample was heated in a stream of nitrogen and hydrogen and the ammonium halides were recovered and titrated potentiometrically (Ag electrode and S.C.E.) with 0.02N AgNOs. The first inflection corresponded to Br- and the second to C1-. Cassani (29) used a coulometric techniquc for chlorine and bromine following closed 5ask combustion. The Br- and C1were titrated sequentially with electrogenerated Ag+ and the end point was determined by derivative potentiometry with a Ag-measuring electrode us. a mercury-HgzS04 reference electrode. For the simultaneous determination of halogens and some other elements, Fedoseev and Osadchii (60) decomposed the sample with powdered magnesium. Nitrogen was determined in a diffusion apparatus whereby the evolved NH3 was collected on a filter paper treated with boric acid solution and determined by titration. The halogens in a separate aliquot were precipitated with a measured excess of 0.01N AgNO3 which was back titrated with 0.01N NHdSCN in the presence of (NH4)2S04-Fez(S04)3 as indicator. For sulfur and halogens, the same authors (166) decomposed the sample as above and transferred an aliquot to the diffusion apparatus. The solution was covered with filter paper impregnated with 0.5N HzSO~and the evolved HzS was trapped on filter paper in the cover of the apparatus. This paper was impregnated with ZnSO4sodium acetate solution which was back titrated with sodium thiosulfate solution. For chlorine and mercury, Marzadro and Lavattiero (127)used a gravimetric procedure. The sample 452 R
0
was ignited at 900 O C in a stream of oxygen and chlorine and mercury were retained, respectively, on silver wire at 540 OC and on silver sponge at 60 O C . Osadchii and Fedoseev (164) decomposed the sample in a closed tube at 800-650 OC with magnesium silicide. For nitrogen, the tube was ground and transferred to a distillation flssk and the nitrogen determined by a Kjeldahltype distillation. The contents of the flask was filtered, acidified, and any sulfur present was distilled off as &S, absorbed in ZnSOd-sodium acetate solution, and determined iodimetrically. The residual solution was titrated with silver nitrate solution for the halogen content. Nuti and Ferrarini (146) determined iodine and sulfur simultaneously after decomposing the sample by closed 5ask combustion. The iodine was extracted into a carbon tetrachloride layer and titrated with 0.007N Na2S208. The sulfur was determined by titration with 0.01M Ba(C104)z in the presence of sulphonazo I11 as indicator. For halogens and copper, Volodina, Gorshkova, and Erofeeva (Mil) pyrolyzed the sample in a nitrogen-hydrogen atmosphere to produce ammonium halides which were converted into the respective acids by ion exchange and titrated with standard base. The residue was dissolved in nitric acid solution and the copper titrated with EDTA solution using murexide as indicator. For the simultaneous determination of calcium and magnesium, Umemoto, Hirose, Sakamoto, Kouri, and Hozumi (227) burnt the sample by the closed flask technique and added the complexan 1,2,bis-(2aminoethoxy)ethane in excess and back titrated with 0.01N CoClz in the presence of 3 ',3'-bis- (3-carboxy-2-h ydroxy - 1 - naphthy1azo)phenolphthalein as indicator for the calcium content. The magnesium was then determined by successive titration with 1,a-diaminocyclohexane-N,N,N',N'-tetraacetic acid using methylthymol blue as indicator. Nakamura, Ono, Kawada (146) determined hydrogen and nitrogen simultaneously by combusting the sample in a vertical combustion tube and passing the products over CuO, C0304, silver, and copper filings, using COZ as carrier gas. The water was absorbed in a special platinum-Pz05 electrolytic cell and the nitrogen was measured in a dispersion-type nitrometer. The water was then electrolyzed and the evolved hydrogen-oxygen mixture (2 :1) was measured in the same nitrometer. For sulfur and iron, Strukova and Lapshova (207) decomposed the sample by oxidative fusion in a bomb containing sodium peroxide. A dilute hydrochloric acid solution of the melt was subjected to column chromatography and the eluate containing sob2- was titrated with 0.01M Ba(NO& with nitchromazo as
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
,indicator. The iron was determined photometrically with sulfosalicyclic acid in a medium of aqueous ammonia. I n order to assem the effect of quenching on the simultaneous determination by liquid-scintillation counting of tritium and sulfur-35, Roncucci, Lambelin, Simon, and Soudyn (176) ran a series of tests using ditrerent levels of radioactivity and four ditrerent dilutions of scintillator for each level. They concluded that for samples of very low activity, best results were obtained at the lowest dilutions. SUBMILLIGRAM SAMPLES
Most of the methods for the submilligram determination of carbon and hydrogen utilize gas chromatographic detection. Belcher and Fleet (17) determined carbon and hydrogen on W p g samples by burning the substance in the presence of CuO a t 750-800 OC in a stream of helium. The products were passed over a cartridge of calcium carbide, the ensuing COZ and acetylene separated on a silica gel column, the acetylene converted into Cot and water, and these products separated on a silica gel column. The two discrete volumes of COZ were detected with a specially designed flow-through katharometer. Umemoto and Hozumi (228) decomposed the sample in a sealed tube which was opened in an evacuated silica tube. The water and COzwere trapped in acetone-solid COZand liquid nitrogen, respectively. After volatilization, the COz and HzO-were passed to a manometer for measurement of the pressure with liquid paraffin as confining liquid. Scheidl (180) described the preparation of some oxygen donors, e.g., MnO2, AgzO, and infusorial earth, for use in a commercial CHN analyzer. With a purified mixture of MnOz and infusorial earth, very low blank values were obtained and the analyzer could be used for the range of 50-150 fig of sample with an absolute error of
