Willis B. Wheeler

Pesticides in Agriculture and the Environment

Three decades of federal integrated pest management policy biological control economic issues of agricultural pesticide use and policy in the United States risk assessment environmental fate of pesticides pesticide residue procedures for rawagricultural commodities - an international view pest management issues on minor crops arthropod resistance to pesticides - status and overview new technologies for the delivery of pesticides in agriculture evolution of the crop protection industry.

Reaction of chlorine dioxide with amino acids and peptides: Kinetics and mutagenicity studies

Chlorine dioxide (ClO2) is currently being considered as an alternate to chlorine as a disinfectant for water treatment. Many organic compounds present in water and food treated with ClO2 are subject to oxidation. 21 amino acids and 3 peptides (L-aspartyl-L-phenylalanine methyl ester (aspartame), L-glycyl-L-tryptophan and L-tryptophylglycine) were studied for their reactivity with ClO2. Chlorine dioxide reacted only with 6 amino acids in 0.1 M sodium phosphate buffer, pH 6.0. The reaction with cysteine, tryptophan and tyrosine was too rapid to be monitored either iodometrically or spectrophotometrically. The reaction with histidine, hydroxyproline and proline was found to be pseudo-first order. ClO2 readily reacted with L-glycyl-L-tryptophan and L-tryptophylglycine but not with aspartame. Mutagenicity studies with the Salmonella microsome assay of the reaction mixtures of ClO2 with those 6 reactive amino acids and the 3 peptides indicated that the reaction products of the 3 peptides, hydroxyproline, and tyrosine exerted mutagenic activity toward both tester strains of TA98 and TA100 in the presence and absence of rat-liver S9 mix.

Solid-Phase Extraction and Capillary Gas Chromatographic Determination of Triazine Herbicides in Water

Abstract A facile and efficient method is described for the determination of trace quantities of triazine herbicides, terbutryn, prometryn and ametryn in water. The procedure involved preconcentration of water samples by sorption on chromatographic grade silica gel particles with chemically modified surface, being covalently bonded with a nonofunctional C8H17 group. This was followed by solvent desorption with 2-propanol. The determinative step was achieved by capillary gas chromatography on Supelcowax-10 fused silica column using a nitrogen-phosphorus detector. The limit of detection was 0.1 μg-10 μgL−1.

Simplified method for the clean-up and reversed-phase high-performance liquid chromatographic determination of benomyl in mangoes☆

The fungicide benomyl (I)’ J, which is methyl1 -(butylcarbamoyl)benzimidazol-2-ylcarbamate according to the International Union of Pure and Applied Chemistry (IUPAC) system, or methyl-l-[(butylamino)carbonyl]-1H-benzimidazol-2-ylcarbamate according to the Chemical Abstracts (C.A.) system, or commonly called methyl-1-(butylcarbamoyl)-2-benzimidazole carbamate controls a wide variety of diseases of fruits, nuts, vegetables, field crops, turf trees and ornamentals. Because of its relatively low mammalian toxicity coupled with effective fungitoxic action in a wide variety of plants, it has been a highly desired chemical for the agroindustries. Consequently, residue data are needed by the regulatory agencies for registration purposes.

Capillary gas chromatographic determination of terbutryn and its degradation products in sorghum grain and confirmation of the compounds by mass spectrometry.

An analytical method with a limit of detection 0.05 mg kg-1 is described for the determination of the herbicide terbutryn and its three degradation products, GS-26575, GS-11355 and GS-26831 in sorghum grains using fused silica capillary gas chromatography. Electron impact and methane chemical ionization mass spectra are reported to confirm the characterization of the compounds. No residues of these chemicals were found in sorghum harvested 14 weeks following terbutryn treatment at 0-4.5 kg ha-1.

Genotoxicity studies of the reaction of chlorine or chlorine dioxide with l-tryptophan

Non-volatile reaction products generated from the reactions of 70 mM aqueous chlorine or chlorine dioxide with 10 mM L-tryptophan were shown to be direct-acting mutagens to Salmonella typhimurium TA100 and TA98. Several of the fluorescent bands obtained after thin-layer chromatographic fractionation of the XAD-2/8 resin concentrates of the reaction mixtures were shown to be more mutagenic than the reaction mixtures using the Ames Salmonella/microsome assay. In addition, these fractions were shown to be capable of increasing significantly the frequency of sister chromatid exchange in Chinese hamster ovary cells in the absence of rat liver S9 mix. GC/MS analysis of the products in a highly mutagenic fraction of the aqueous chlorine reaction products identified 1,1,3-trichloropropanone, 1,1,3,3-tetrachloropropanone and dichloroquinoline.

Improved derivatisation method for the gas-liquid chromatographic determination of the herbicide oryzalin

A rapid derivatisation method is described for the determination of the herbicide oryzalin. It involves the use of dimethylsulphinyl anion and methyl iodide or ethyl iodide. Gas-liquid chromatography is used with either an N-P or an electron-capture detector. The method was applied to the residue analysis of fortified sweet potatoes, soils and water. With an electron capture detector, residues as low as 0.01 µg g–1 in sweet potatoes and soils and 0.001 µg g–1 in water may be detected. For an N-P detector the limits of detection are 0.05 µg g–1 in sweet potatoes or soils and 0.005 µg g–1 in water. Recoveries ranged from 80–90% from these matrices at fortification levels of 0.08–0.5 µg g–1. The choice of using either the methyl or the ethyl derivative is an added advantage.