Grain Fumigant Determination. Wheat as a Chromatographic Column toward Methyl Bromide, Ethylene Dibromide, Acrylonitrile, Chloropicrin, and Carbon Tetrachloride in the Vapor Phase

Abstract

Methyl bromide, ethylene dibromide, acrylonitrile, and chloropicrin were applied in the vapor phase, both singly and in admixture with carbon tetrachloride, to the surface of 7-foot columns containing wheat of 12, 16, and 20y0 moisture content, respectively. Air was used as a carrier gas and the composition of the gas-air mixture that emerged from the bottom of each column was assessed polarographically. Chloropicrin, acrylonitrile, and especially ethylene dibromide were strongly sorbed, particularly at 1 6 and 20% moisture. Even up to 13 days at 25' C., ethylene dibromide emerged only in small amounts and at 4.5' C. was consistently zero. Acrylonitrile showed an interesting delayed action. Carbon tetrachloride, which in itself is a mediocre fumigant, increased the peak output of each of the other fumigants at the various temperature and moisture levels under test. Carbon tetrachloride also extended the time when zero concentration was reached. The results were in agreement with earlier work with methyl bromide, ethylene dibromide, and carbon tetrachloride applied in the liquid phase. It is postulated that carbon tetrachloride vapor may act as an eluting agent, with wheat acting as a chromatographic column. The proportions of acrylonitrile-carbon tetrachloride, chloropicrin-carbon tetrachloride, etc., that emerged from the bottom vary with dosage, time, and the temperature and moisture content of the column, and in any event differ considerably from the proportions initially applied. It follows that biological evaluation of fumigants needs analytical data for correct interpretation of results.

Cereal Sorption of Grain Fumigants, Sorption of Ethylene Dibromide, Ethylene Dichloride, and Carbon Tetrachloride by Cereal Products

“…This report deals with the sorption by 51 cereal substrates of ethylene dibromide, ethylene dichloride, and carbon tetrachloride (EDB, EDC, and CT) applied singly and in two admixtures in the vapor phase at 27°C. Methods using gas chromatography (5) were developed which were more specific, sensitive, and rapid than the polarographic methods (1,4,8) used in previous investigations of fumigant behavior (2,3,6,9) and enabled the use of 100-cc. syringes as micro fumigation chambers and smaller gas-air samples for analysis, and more rapid attainment of equilibria.…”

Grain Fumigant Determination, Polarographic Determination of Methyl Bromide, Ethylene Dibromide, Acrylonitrile, Chloropicrin, and Carbon Tetrachloride in Air

“…The gas absorption assembly (Figure 1) worked well, and was modified for sampling of grain columns (7) and glass fumigation flasks (8) to give results reproducible to within ±2.3% in the range 0.25 X 10-4 to 10~4M. The efficiency of gas absorption of a single absorption tube was 98 to 100%, as determined by placing a second tube in series with the first.…”

“…The method for acrylonitrile was adapted for such a purpose (4). Measurement of fumigant residues of grain in columns (7) was not within the terms of reference of the investigation and residues were therefore not determined. In addition to applications for residue problems of concern to agricultural research and Food and Drug Administration agencies, the methods may be applied to research in air pollution, plant and animal toxicology, industrial processing, reaction kinetics, etc.…”

“…In the initial stages of development of the methods, carbon tetrachloride was determined spectrophotometrically by (7) Fallscheer, H. O., Cook, J. YV., J.…”

“…similarly time-consuming and, in addition, the presence of carbon tetrachloride in high concentrations affected the accuracy of measurement. The titrimetric method (7) for acrylonitrile was accordingly replaced in this work by adapting the polarographic method of Fuller and Norris (72) in which the cathodic wave of acrylonitrile (£1/2 = approximately -2.1 volts vs. S.C.E. in aqueous solution with 0.05M tetramethylammonium hydroxide as supporting electrolyte) afforded direct measurement in amounts as low as 1.08 X 10acrylonitrile with no interference from carbon tetrachloride.…”