Phosphine gas (PH3) was applied at concentrations of 0.15 to 0.60 mg. per liter to wheat, oats, barley, flax, and milled grain products in closed containers. No free PH3 remained in any of the substrates after accelerated aeration with nitrogen. Irreversible sorption, considered chemisorption by the author, was reproducibly obtained under the experimental conditions employed. The amount of PH3 chemisorbed was mainly affected by the type, moisture content, and physical form of the substrate, as well as by temperature and contact time. With milled wheat products, the uptake of PH3 by wheat gluten powder, middlings, bran, and shorts was greater than that by wheat starch, flour, and wheat germ. For four different concentrations used, the absolute amounts of PH3 sorbed were directly proportional to the amounts applied, as for first-order reactions. Presumptive evidence that PH3 binds with proteins and complexes with mineral components of the substrates is discussed.

No abstract

No abstract

Microcoulometric, thermionic, and flame photometric (phosphorus mode) detectors used with GLC were compared for minimum detectability, accuracy, reproducibility, and rapidity for the measurement of ppb and ppt levels of phosphine, PH3, in foodstuffs, air, and water. Based on a response at 10% of recorder scale with a reproducibility to within ±10%, the lower limits of detectability were: microcoulometric (peak area), 5 nanograms; thermionic (peak height), 20 picograms; flame photometric (peak height), 5 picograms. With a 10-g. sample of foodstuff or water, these amounts correspond to a relative minimum detectability of 500, 2, and 0.5 ppt for the microcoulo-

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.