A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water.

A multiresidue analytical method is described for pesticides, transformation products, and related toxicants based upon high performance liquid chromatographic (HPLC) fractionation of extracted residue on a Partisil silica gel normal phase column followed by selective-detector gas chromatographic (GC) determination of components in each fraction. The HPLC mobile phase gradient (hexane to methyl t-butyl ether) gave good chromatographic efficiency, resolution, reproducibility and recovery for 61 test compounds, and allowed for collection in four fractions spanning polarities from low polarity organochlorine compounds (fraction 1) to polar N-methylcarbamates and organophosphorus oxons (fraction 4). The multiresidue method was developed for use with air samples collected on XAD-4 and related trapping agents, and water samples extracted with methylene chloride. Detection limits estimated from spiking experiments were generally 0.3-1 ng/m3 for high-volume air samples, and 0.01-0.1 microgram/L for one-liter water samples. Applications were made to determination of pesticides in fogwater and air samples.

Comparison of an enzyme-linked immunosorbent assay and a gas chromatographic procedure for the determination of molinate residues.

An enzyme-linked immunosorbent assay (ELISA) was compared to a gas chromatographic method for the analysis of the thiocarbamate herbicide molinate (S-ethyl hexahydroazepine-1-carbothioate). Apparent recoveries from water spiked at 1 ppb to 1 ppm levels were comparable when liquid-liquid extraction was used. Solid-phase extraction was also examined and apparent recoveries by both ELISA and gas chromatography (GC) were comparable to each other as well as to the liquid-liquid extraction method. Methanol, acetonitrile, and ethyl acetate were equally effective in eluting molinate from solid-phase columns. An excellent correlation was obtained between the ELISA and GC method for field-treated water samples extracted by using the solid phase method and either ethyl acetate or methanol as the eluting solvent. Air and soil samples from this same study correlated well when analyzed by ELISA or GC, but ELISA results for soil were generally higher than GC data and of slightly lower precision than GC. Tests with a coated plate, pipettors, and the plate reader amounted to 8.0% error, the majority of which was attributable to the coating antigen binding and to antigen-antibody reactions.

Anaerobic microbial dechlorination: an approach to on-site treatment of toxaphene-contaminated soil.

Enhanced microbial degradation of toxaphene by natural microorganisms occurred in soil and sediment amended with organic matter kept under anaerobic (flooded) conditions. Laboratory experiments yielded a dissipation half-life of approximately 3 and 1 week for soil and sediment, respectively, containing 10 ppm of technical toxaphene and a 1% alfalfa meal amendment. Dissipation was accompanied by an increase in early eluting gas chromatographic peaks and a decrease in later eluting peaks, indicating that dechlorination had occurred. Enhanced anaerobic dissipation also took place in soil containing 500 ppm of toxaphene, although at a lesser rate than at 10 ppm, and when cotton gin waste was used as amendment in place of alfalfa meal. Sediment in a toxaphene-contaminated pesticide waste disposal ditch was amended with 10% steer manure and flooded to ascertain field utility of the technique for on-site decontamination. Toxaphene residues were reduced from 63 to 23 ppm in 120 days, and some degradation activity still occurred up to 8 months after this single treatment.

Cardenolide connection between overwintering monarch butterflies from Mexico and their larval food plant,Asclepias syriaca.

The majority (85%) of 394 monarch butterflies sampled from overwintering sites in Mexico contain the same epoxy cardenolide glycosides, including most conspicuously a novel polar glycoside with a single genin-sugar bridge (aspecioside), as occur in the milkweedsAsclepias speciosa andA. syriaca. This cardenolide commonality was established by isolating aspecioside and syriobioside from the wings of overwintering monarchs and the two plant species, and comparing Chromatographie and NMR spectrometric characteristics of the isolates. When combined with the migratory pattern of monarchs and the distribution of these two milkweed species, this chemical evidence lends strong support to the hypothesis thatA. syriaca is the major late summer food plant of monarchs in eastern North America. This finding may be of ecological importance, forA. syriaca contributes less cardenolide and cardenolides of lower emetic potency to monarchs than most milkweeds studied to date.

Residues of toxaphene, DEF, and paraquat in plant parts and gin waste from a treated cotton field.

The origin and fate of the gin waste residues of three chemicals--toxaphene, DEF, and paraquat--used frequently in cotton production in California were studied. Residues were determined for foliage and bolls in the live plants, for lint and seed in harvested seed cotton, and for gin waste and its lint and non-lint components, following commercial treatments to the cotton crop. Gin waste residues were followed during five months of open storage to ascertain dissipation rates in a typical waste sample. Relatively high residues of each of the three chemicals persisted at harvest, during storage prior to ginning, and in stored gin waste. The major proportion of gin waste residue was associated with the non-lint components--leaf parts, burrs, stems and other foreign matter. Average stored gin residues in the lint and non-lint components were 13 and 60, 11 and 58, and 5 and 10 ppm for toxaphene, DEF, and paraquat, respectively, during the open storage period.