oxygen, and tin may form monoxide first and then decompose to atoms. The lateral diffusion and the formation of a large amount of the third species other than atom and monoxide would cause errors in the atomization mechanism mentioned above. The lateral diffusion, however, does not seem to have a serious effect, as the flame widths with respect to temperature (2, 1 8 ) , flame components (29, 30) and metal atoms (3,29) do not greatly change in the crucial range of 5- to 20-mm burner height. I t was not confirmed in our experiment if the large amounts of the third species are formed. The formation of a higher oxide of tin, SnO,, or hydroxide may be possible in the acetylene-lean region, but it seems difficult in the acetylene-rich region because of high reduction potential and low concentration of OH.
LITERATURE CITED (1)N. V. Mosshoider. V. A. Fassel, and R. N. Kniseley, Anal. Chem., 45, 1614 (1973). (2)J. B. Willis, Spectrochim. Acta, Part A, 23, 81 1 (1967). (3)J. B. Wiiiis, Spectrochim Acta, Part E, 25, 487 (1970). (4)V. A. Fassel. J. 0. Rasmuson. R. N. Kniseley, and T. G. Cowiey, Spectrochim Acta, Part 8, 25,559 (1970). (5) R . Smith, C. M. Stafford, and J. D. Winefordner, Anal. Chim. Acta, 42, 523 (1968). (6)P. J. Th Zeegers, W. P. Townsend. and J. D. Winefordner, Spectrochim. Acta, Part 5,24, 243 (1969). (7)C. L. Chakrabarti and S. P. Singhal. Spectrochim. Acta, Part 8, 24, 663 (1969). (8)T. J. Vickers, C. R. Cottreil, and D. W. Breakey, Spectrochim. Acta, Part 8,25,437 (1970). (9)A. Ando, K. Fuwa, and B. L. Vallee, Anal. Chem., 42,818 (1970). (10) K. Fujiwara, H. Haraguchi, and K. Fuwa. Anal. Chem., 44, 1895 (1972). (11) K. Fujiwara, H. Haraguchi. and K. Fuwa, Chem. Lett., 1973,461.
(12) K. Fujiwara, Masters thesis, The University of Tokyo, March 1972;K. Fujiwara, H. Haraguchi, and K. Fuwa, 21st Annual Meeting of Japan SOC.for Anal. Chem. at Sendai, Sept. 1972. (13) K. Fuwa, Fourth int. Conf. on Atomic Spectroscopy, Toronto, Canada, Nov. 2,1973. (14)R . K. Skogerboe, A. T. Heybey, and G. H. Morrison, Anal. Chem., 38, 1821 (1966). (15)H. Haraguchi and K. Fuwa, Chem. Lett., 1972,913:. (16) R. W. B. Pearse and A. G. Gaydon, "The Identification of Moiecuiar Spectra," Chapman and Hail, London, 1950. (17)B. W. Bailey and J. M. Rankin, Anal. Chem., 43,219 (1971). (18)W. Sneiieman, "Flame Emission and Atomic Absorption Spectrometry," J. A. Dean and T. C. Rains, Ed., Marcel Dekker, New York. N.Y.. 1969, p 213. (19)R . F. Browner and J. D. Winefordner, Anal. Chem., 44,247 (1972). (20)I. Reif, V. A. Fassel, and R. N. Kniseley, Spectrochim. Acta, Part 8, 29,
79 (1974). (21)A. G. Gaydon, "Dissociation Energies and Spectra of Diatqmic Molecules," 3rd ed,, Chapman and Hall, London 1968. (22)JANAF, Thermochemical Tables, Prepared by Dow Chemical Co., Midland, Mich. 1966,1967,1968. (23)D. R. Jenkins and T. M. Sugden, "Flame Emission and Atomic Absorption Spectrometry," J. A. Dean and T. C. Rains, Ed.. Marcel Dekker, New York, N.Y.. 1969,p 151. (24)C. Th. J. Alkemade, "Analytical Flame Spectroscopy," R. Mavrodineanu, Ed., Springer-Verlag. New York, N.Y.. 1970,p 28. (25)J. E. Chester, R. M. Dagnall, and M. R. G. Taylor. Anal. Chim. Acta, 51,
95 (1970). (26)T. G. Cowiey, V. A. Fassel, and R. N. Kniseley, Spectrochim. Acta, Part 6,23,771(i968). (27)V. K. Paday, Anal. Chim. Acta, 57,31 (1971). (28) S.R. Koirtyohann and E. E. Pickett, Spectrochim. Acta, Part B, 26, 349 11971) \ .I
(29)C. S.Rann and A. N. Hambly, Anal. Chem., 37,879 (1965). (30) S. Musha and S. Shimomura, "Atomic Absorption Analysis," Kyoritsu, Tokyo 1972,p 75.
RECEIVEDfor review May 9, 1974. Accepted December 5, 1974.
Determination of Methyl Alcohol in Wine by Gas Chromatography C. Y. Lee, T. E. Acree, and R. M. Butts Department of Food Science and Technology, Cornell University, Geneva, N.Y. 14456
Dietary methyl alcohol is derived in large part from fresh fruits and vegetables. It occurs as free alcohol or esterified with fatty acids, or as a product from the hydrolysis of methoxy groups on polysaccharides such as pectin. Methyl alcohol in alcoholic beverages is often of concern to the public because of its toxicity. The conventional colorimetric method for the analysis of methyl alcohol is tedious and time-consuming ( I ) . Dyer ( 2 ) analyzed methyl alcohol by gas chromatography using a polar Carbowax 1500 on Chromosorb W column described by Brunelle ( 3 ) .However, the separation of methyl alcohol from ethyl alcohol was marginal. Di Corcia et al. ( 4 ) achieved a greater separation of the two alcohols by using a column of polyethylene glycol 1500 on graphitized carbon. However, the retention time of acetaldehyde was very close to that of methyl alcohol. Recently, an ethylvinylbenzene polymer (Porapak) has been introduced to separate polar organic compounds. I t gives retention times which are a linear function of the molecular weights of the compounds ( 5 ) . Therefore, the common low molecular weight organic compounds found in alcoholic beverages, i.e. methyl alcohol, acetaldehyde, ethyl alcohol, ethyl acetate, etc., should be easily separated on this packing material. In this note, a simple gas chromatographic procedure using Porapak QS is introduced for the analysis of methyl alcohol in wine a t concentrations as low as 5 ppm by direct injection.
EXPERIMENTAL Apparatus. A Varian Aerograph 200 gas chromatograph equipped with a flame ionization detector was used. A coiled stainless steel column (2-m long X 0.2-cm i.d.) was washed thoroughly (6) and packed with Porapak QS (silylated ethylvinylbenzene polymer). New columns were conditioned at a temperature of 210 "C for 24 hours. The gas chromatograph operating conditions were as follows: the nitrogen carrier gas flow rate was 40 ml/min under a column head pressure 25 psig, the injector port and detector temperatures were 210 and 220 "C, respectively. The column was operated isothermally a t 115 O C . A Hamilton syringe (10 pl) was used to inject samples of 3 GI. Reagents. Methyl alcohol (reagent grade) obtained from Fisher Scientific Company and distilled water were used to prepare solutions of methyl alcohol of varying known concentrations. Procedure. Standard solutions were analyzed every day by injecting 3 pl of aqueous solutions of methyl alcohol of known concentrations in the range of 10 to 1000 ppm. A calibration curve was prepared by plotting the concentration in ppm vs. a response factor (peak height multiplied by the attenuation). T h e concentration of methyl alcohol in 3 p1 of an unknown sample was then determined by calculating the response factor and relating it t o calibration curve values.
RESULTS AND DISCUSSION A 2-m Porapak QS column gave good separation and resolution of the four important low molecular weight volatiles commonly found in alcoholic beverages. These compounds are methyl alcohol, acetaldehyde, ethyl alcohol, ANALYTICAL CHEMISTRY, VOL. 47. NO, 4, APRIL 1975
747
Table I. Recovery of Methyl Alcohol Added to a Wine Sample
+
methanol, PPm
Wine Wine Wine Wine Wine Wine
+ 10 + 25
+ 50 + 75
+ 100
Methanol found, PPm
Recovery, /o
...
17.1 27.7 42.4 65.9 90.2 117.2
106.1 101.2 97.6 97.4 100.1
Av 100.4
0
2
4
6
8
RETENTION TIME (MlNJ
typical gas chromatogram of Concord wine on Porapak OS column using flame ionization detector (FID) Figure 1. A
I) water, 11) methanol, Ill) acetaldehyde, and IV) ethanol
and ethyl acetate which had retention times of 1.8, 2.8, 4.0, and 19.5 minutes, respectively. Figure 1 shows a typical chromatogram of a Concord wine. The calibration curve for methyl alcohol was linear over the range of 10 to 1000 ppm and good recovery was obtained when methyl alcohol was added to a wine sample, e.g., Table I. The average recovery on 20 runs during a 5-day period was 100.6% with a standard deviation of f4.4%. To prevent interference from the buildup of organic matter in the system, the column was heated overnight at 200 O C and the glass insert in the injector port was changed every 3 days. Using this method, the methyl alcohol contents of 20 commercial wines ranged from 50-325 ppm.
Unlike other chromatographic support and substrate systems, ethylvinylbenzene polymers (Porapak) are durable and require no special handling in their separation and use, and Porapak QS yields an excellent separation of the common constituents of alcoholic beverages. The gas chromatographic procedure presented here can be completed in as little as 7 minutes and is a simple and accurate method for the routine analysis of methyl alcohol in alcoholic beverages. LITERATURE CITED (1) "Official Method of Analysis," Association of Official Analytical Chemists, 1 I t h ed., 1970,p 153. (2) R. H. Dyer, J. Assoc. Offic. Anal. Chem., 54, 785 (1971). (3)R. L. Brunelle, J. Assoc. Off. Anal. Chem., 50, 321 (1967). (4)A. Di Corcia, A. Liberti, and R. Samperi, Anal. Chern., 45, 1228 (1973). (5) R. N. Baker, A. L. Alenty, and J. F. Zack. Jr., J. Chrornatogr. Sci., 7,312 ( 1969). (6)T. R. Mon. Res./Dev., 22 (12),14(1971).
RECEIVEDfor review September 20, 1974. Accepted December 18,1974.
Gas Chromatographic Determination of Carbon in Fertilizer Materials David Bennett Fisons Limited-Ferfilizer Division, Levington Research Station, Ips wich, Suffolk. UK
A fertilizer manufacturing process involving the ammoniation of phosphoric acid in molten ammonium nitrate requires careful monitoring of carbon in the range 0.01 to 0.05%. In the original method of determination, carbon was oxidized to carbon dioxide which was weighed a.fter absorption on soda asbestos. For accurate analysis, it was necessary to separate quantitatively about 3 ml of carbon dioxide from a mixture containing some 8 liters of water vapor and 4 liters of nitrogen and nitrogen oxides, and to absorb the carbon dioxide quantitatively and specifically before weighing. Because of the difficulties involved in performing this analysis satisfactorily, unacceptable delays of 2-3 hours occurred. Several commercial instruments are available for carbon analysis, designed mainly for use with organic materials having significant carbon contents. Normally, these analyzers employ microgram quantities which aid oxidation and result in small gas samples that can be analyzed directly by, for example, gas chromatography. Such small samples of fertilizer would not be representative, and the low car748
ANALYTICAL CHEMISTRY. VOL. 47,
NO. 4 , APRIL 1975
bon contents involved would require equipment of very high sensitivity. The use of gas chromatography for the determination of carbon in various materials has been previously reported. In general, the methods are rapid and the precision and accuracy are similar to classical methods. One difficulty in their use is the need to introduce plug samples of gas into the chromatograph. Previous methods for achieving this involved collecting the oxidation products in liquid nitrogen traps (1-3) or on solid absorbents (4-7), or the use of rapid oxidation methods, e.g., high frequency induction furnaces (8-1 1 ) or direct injection of liquid samples onto heated oxidants (12-15). These methods either add considerably to the analysis time, or to the cost of the equipment, or are unsuitable for fertilizer materials in which the carbonaceous matter can be largely water insoluble. To provide a rapid, accurate analysis the following method was developed, based on the oxidation of carbonaceous material to carbon dioxide, followed by chromatographic analysis of samples of the gas. Wet oxidation using the acid
