Biomedical subjects
Publications and source records attributed to F A Gunther.
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A colorimetric technique has been developed which is suitable for use as a field-screening method for detecting above-tolerance levels of parathion on and in citrus fruits. By using this method, a grower should be able to postpone harvesting a crop until parathion residues are below tolerance level, so that the crop is safe to market. The method depends on the reaction of parathion with 4-(p-nitrobenzyl)-pyridine. Parathion is extracted by mixing chopped citrus rind with acetone in a hand-operated homogenizer. The extract is partially cleaned by a partitioning step before final cleanup with a Sep-Pak Florisil cartridge. The colored reaction solution is read at 560 nm by using a portable, rechargeable spectrophotometer. A single test can be completed in about 75 min; the average time per test when several are conducted sequentially is considerably shorter. The analytical system responds readily to less than 5 ppm parathion on or in 1 g navel orange rind, which corresponds to less than 1 ppm in the whole fruit. The present U.S. tolerance for parathion on or in citrus is 1 ppm on a whole fruit basis. Preliminary work indicates that the method should also be suitable for apples.
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A field screening method has been developed for detecting above-tolerance residues of dithiocarbamate (DTC) fungicides on fruits and vegetables. A harvested crop might be condemned as unfit for market if above-tolerance DTC residues are present; however, by using this screening method, a grower might be able to postpone harvesting a crop until the screening test indicates that residues have dissipated below the tolerance level. The method depends on carbon disulfide generated from DTC fungicides at an elevated temperature into the headspace gas above the contents of a septum-sealed reaction flask, with hydrochloric acid and stannous chloride present. The syringe-withdrawn, headspace carbon disulfide then reacts with the appropriate chromophore reagent already in the syringe. The lower limit of detectability is about 2 ppm DTC fungicide from 30 g chopped crop. A single test can be completed in about 90 min; the average time per test when several are conducted sequentially is considerably shorter.
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Dialifor and methidathion were added to diluted "Zinfandel" grape concentrate at 25 ppm and dimethoate at 1.0 and 25 ppm prior to fermentation with Saccharomyces cerevisiae. The finished wine 56 days later contained 10% (2.5 ppm) of the dialifor, 46% (12 ppm) of the methidathion and 85% (21 and 0.98 ppm) of the dimethoate added to the grape must. Residues in wine stored at 24 degrees C dissipated by hydrolysis; half-lives in wine were 7 days for dialifor and methidathion and 30 days for dimethoate. Residues were unchanged in wine in frozen storage for one year. Analysis of seven commercial wines for dimethoate indicated less than 0.03 ppm dimethoate was present; identity could not be confirmed by thin-layer chromatography at this level.
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"Semellon" grape juice fortified with a high level of 25 ppm parathion was fermented using Saccharomyces cerevisiae var. ellipsoideus. After 12 days inte parathion levels in the wine and lees were 10.3 and 156 ppm, respectively; the paraoxon, aminoparathion, and p-nitrophenol levels in the wine were 0.16, 0.20, and 4.5 ppm, respectively, and in the lees were 0.04, 3.1 and 10 ppm, respectively. Thus, hydrolysis of parathion to p-nitrophenol and parathion sorption to sedimented particulate matter were important pathways for parathion residue reduction in the wine. The 56-day-old finished wine just prior to bottling contained 8.8 ppm parathion, 0.04 ppm paraoxon, 0.21 ppm aminoparathion, and 3.0 ppm p-nitrophenol. Two months storage at 24 degrees, 12 degrees, 4 degrees, and -20 degrees C had no effect on paraoxon and aminoparathion residue levels in the wine; parathion residues in wine decreased at all storage temperatures.
Several types of fabrics were laboratory-tested for their effectiveness in workers protection to pesticide-laden dust encountered in the agricultural environment. Of the applied less than 100 mesh dust, penetrations through knitted jersey and woven fabrics were greater than 87% and less than 5.8%, respectively. Treatment of woven fabrics with fluorocarbon polymers curtailed penetration by greater than 60%. Nonwoven fabrics allowed less than 0.5% dust penetration. Parathion mixed with 100-mesh sieved dust resulted in increasing "ppm" levels with decreasing particle size; extent of parathion conversion to paraoxon was independent of particle size for the sandy loam dust used.
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