Organic Elemental Analysis T. S. Ma* Department of Chemistry, City University of New York, Brooklyn, N. Y. 112 10
Milton Gutterson Flavor Application Laboratory, Dragoco, lnc., King Road, Tofowa, N.J.
GENERAL This review on quantitative analysis of the elements present in organic materials follows the last one ( 1 ) but covers only the period from September 1974 to December 1975. For the literature that appeared during the early part of 1974, the reader is referred to the book recently written by the senior author (2). This book also presents summaries of the publications that were cited in the previous reviews. Furthermore, since the Biennial Review covers published papers only, a number of unpublished innovations and modifications, which the senior author has learned on his visits to practicing analysts, will be found in the various chapter of the forthcoming book. Recent research activities in organic elemental analysis fall into several categories. Much attention has been given to the apparatus and techniques of decomposition. This is understandable since, if decomposition of the organic material is not quantitative, all subsequent steps of determination are wasted. Kozlowski (3) described a vertical combustion assembly for the decomposition of heterocompounds and polymeric materials by the flash combustion method. The combustion tube, of annular cross-section, is heated by an internal electric heater; the temperature can be regulated externally. It can be used for the determination of C, H, N, halogens, and S. Trutnovsky (4) proposed the determination of nitrogen by combustion in a fast stream of oxygen. The oxygen is produced electrolytically and the hydrogen generated simultaneously is used to reduce the excess oxygen and oxides of nitrogen. Mlejnek ( 5 ) determined N, C, and H by decomposition in glass ampoules; the products were analyzed by gas chromatography. This mode of finish was also studied by other workers (6, 7 ) . Floret (8) designed a vertical combustion tube for the determination of halogens; the sample, contained in an aluminum capsule, is heated at 950-1000 "C in a stream of oxygen. Combustion catalysts such as cobalt oxides ( 9 ) , other metal oxides ( I O ) , and potassium permanganate (11) continued to be investigated. Mass spectrometry was used by Walisch (12) to study combustion procedures. Thurauf employed infrared spectrometry to determine C, H, 0, and S in coal (13). Merz (14) and Hakariya et al. (15)reported on data processing for automated elemental analysis. CARBON A N D HYDROGEN Binkowski ( 1 6 ) described a rapid gravimetric procedure for C and H using the flash combustion method. The specially designed absorption vessels are rapidly transferred and accurately placed on the pan of the adjacent, appropriately shielded, semimicro balance by a simple arrangement operated by two twist knobs. Karlsson (17) performed coulometric determination of both C and H by aquametry based on the Karl Fischer method, C02 being converted to H20 by LiOH at 215 "C. For gas chromatographic determination, H20 is preferably converted to COz in a tube containing a mixture of a-naphthylisocyanate and 1,4-diazabicyclo[2.2.2]octaneimpregnated on Chromsorb P-AW (18). The techniques for handling difficult compounds were reported by several groups of investigators. The samples included highly halogenated substances (19), heterocyclics (201, fluoro and perfluoro compounds (21,22), phosphorus compounds (23,24), and compounds containing sulfur, silicon, and metallic elements (25). Methods were proposed
075 12
for assaying radioactive C and H in biological material (261, and 14C or 3H in organs (27).
OXYGEN A patent was issued to Honma (28) for a method to determine oxygen. The sample is decomposed over platinized carbon in the presence of hydrogen or methane which serves to remove oxygen-containing substances in the catalyst. Helium is used as the carrier gas. The resulting CO from the sample is converted to COz by means of CuO or 1 2 0 5 . The final step involves either gravimetric determination of C02 or titrimetric determination of 12. Imaeda et al. (29) reported on the determination of oxygen by carrier gas methods. Campiglio (30) compared the efficiency of different methods for eliminating interferences Trom sulfur. Maximum reproducibility and accuracy were obtained when the CSz and COS were removed by cooling a t -196 "C, or by use of N-H (9:l) as carrier gas, or by thermal decomposition on Ni a t 600 "C or on Zn at 350 "C. The last method was recommended as most practical.
NITROGEN Automated procedures for the Kjeldahl method continue to be evolved (31-34). A rapid coulometric procedure was developed by Bostrom et al. (35). Forty samples are digested simultaneously using the Tecator system. The digestion products are diluted to 75 ml, and 1 ml is coulometrically titrated in 1-2 min: 20-30 determinations can be performed per hour. A number of workers studied the digestion media, conditions, and catalysts. Batey et al. (36) recommended H2SO-HC104 for plant material but the HC104 should be substantially diluted with HzSO4 so as to prevent losses of N due to local high concentration of HC104. Glowa (37) proposed ZrO2 as catalyst in place of the environmental pollutant HgO. Horacek and Sir (38) reported on the influence of halogens and many metals when the digestion was performed in a sealed tube containing sulfuric acid. When Raney nickel and HzS04 were used to reduce N-0 compounds, Tanabe (39) found that hydroxylamine and hydrazine sulfates, and isoniazid were fully decomposed, while semi-carbazones and phenylhydrazones yielded only 1 mol of NH3 per N=N; oximes that volatilize on heating with H2SO4 could not be determined by this method. When phosphinic acid was employed, Chiba and Takata (40) observed that most nitro, nitroso, azo, and hydrazido compounds could be analyzed accurately, but hydrazine derivatives and volatile compounds like p-chloronitrobenzene and m -dinitrobenzene gave incorrect results. Lunder ( 4 1 ) and Kreutzer (42) described automated N analyzers based on the Dumas principle. For the decomposition of amines and hydrazines containing N-methyl or N-ethyl groups, Abramyan et al. (43) recommended CuO in the presence of KMn04. For the gas chromatographic determination of nitrogen in chlorine-containing compounds, Mamina et al. (44) mixed the sample with CuO and combusted at 820 "C in a stream of He in a silica tube packed successively with Ag (4 cm), CuO (4 cm), and Cu ( 5 cm). The C02, HzO, and Clz produced are absorbed by Mg(C104)Z and Ag, respectively, and the Nz is determined on a column (30 cm X 6 mm) packed with active carbon. Another gas chromatographic procedure was described by Sketova et al. (45). ANALYTICAL CHEMISTRY, VOL. 48,
NO. 5,
APRIL 1976
101 R
Table I. Trace Analysis of the Elements in Organic Materials Element determined
Non-metals Nitrogen Oxygen Sulfur Fluorine Chlorine Bromine Iodine Phosphorus Metalloids Arsenic Boron Selenium
Material analyzed
Cadmium Chromium Cobalt Copper Gold Iron Lead Lithium Magnesium Manganese Mercury Molybdenum Plutonium Tha Iliu m Tin Zinc
Color Gasometric Emission spectr. Neutron act. Potentiometric Coulometric Radioactivity Titrimetric Gas chromat. Color Turbidimetric X-ray fluorescence X-ray fluorescence Color Kinetic Color Neutron act.
(116, 1 1 7 ) (118) (119) (120) (121 1 (122, 1 2 3 ) (124-126) (127) (128) (129, 1 3 0 ) (131 1 (132) (133) (134) (135) (136) (137)
Plants, wines, vinegar Biological Biological Plants, papers Biological
Color Atomic absorp. Emission spectr. Fluorimetric Neutron act.
(138, 139 (140, 141 (14 2 ) (143, 144 (145)
Plants Biological Biological Biological Blood, wine Biological, wines Petroleum, foods, biological Biological Blood Biological Pharmaceutical Plants, animal feeds Biological, foods Plants, edible oils Blood Blood, wines, juices Foods, blood, urine Blood Meat
Color Radioactivity Atomic absorp. Gas chromat. Color Atomic absorp. Atomic absorp. Neutron act. Atomic absorp. Chemiluminescence Color Atomic absorp. Color Atomic absorp. Atomic absorp. Color Atomic absorp. Atomic fluorescence X-ray fluorescence Atomic absorp. Atomic absorp. Atomic absorp. Coulometry Atomic absorp. Mass spectr. Color Neutron act. Radioactivity Color Polarography Color Neutron act. Atomic absorp. Atomic fluorescence
(146) (147) (148) (149) (150, 1 5 1 ) (152, 1 5 3 ) (115, 154-157) (158) ( 159,' 1 6 0 ) (161) (1 6 2 ) (1 63, 1 6 4 ) (1 6'5-1 6 7 ) (1 68-1 7 0 ) (1 71 ) (172, 1 7 3 ) (1 74-1 79 )
Blood
Wines Petroleum, biological Biological Foods, biological Plants Plants, biological Biological Urine Biological Urine Foods Biological Petroleum Biological
Carpenter and La Fleur (46)determined nitrogen in biological materials by the nuclear-track technique in which proton tracks from the reaction I4N(n,p)l4C (initiated by thermal neutrons) can be observed in cellulose nitrate. Average values for the analysis of orchard leaves and bovine liver were 2.70 f 0.09 and 10.82 f 0.24%, respectively, the corresponding values obtained by the Kjeldahl method being 2.755 f 0.038 and 10.59 f 0.04%. Scott and Humpherson ( 4 7 ) described the determination of 15N by electrodeless discharge. Nitrogen is generated by the Dumas method from, e.g., a bacterial culture, and is sealed into discharge tubes at a pressure of 2 to 7 Torr. When the concentration of 15N is
