Imidazole: fungitoxic derivatives.

Study of several new types of fungitoxic derivatives of imidazole reveals that imidazoles substituted on the imine nitrogen atom are likely to be active if the substituent is electron-attracting, and if the atom connecting it to the imidazolyl moiety has tetrahedral geometry. Fungitoxicity is high with phosphinamidothionate and triarylmethyl groups as substituents. The presence of an asymmetric phosphorus atom in the substituent has no effect on fungitoxicity, but affects mammalian toxicity.

Solubilities of pesticide chemicals in water. Part I: Environmental physical chemistry.

It is hoped that this review of the equilibrium aqueous solution thermodynamics and environmental partitioning tendencies of chemicals will be valuable in elucidating the behavior of pesticide chemicals in the environment and in promoting the development of more reliable correlations between physical chemical measurements and environmental partitioning coefficients. Ultimately the success of both the thermodynamic and environmental interpretations depend on having reliable, critically reviewed data from both laboratory and the "field."

Quantitative integration of the Salmonella microsuspension assay with supercritical fluid extraction of model airborne vapor-phase mutagens.

Vapor-phase mutagens are potentially a major class of toxic contaminants in ambient and indoor air. These compounds are not routinely analyzed due to a lack of an established integrated methodology to quantitatively trap, extract and test the compounds in a bioassay. In a previous report, we emphasized the trapping of volatile and semi-volatile mutagens and the extraction of these compounds using supercritical carbon dioxide (CO2). In the present study, we discuss the use of a bioassay for the quantitation of the model mutagens, ethylene dibromide(EDB) and 4-nitrobiphenyl (4-NB), trapped from an airstream. The compounds EDB and 4-NB were released into a controlled airstream, trapped on XAD-4 adsorbent, and were extracted using supercritical CO2. The extract was tested in a microsuspension modification of the Ames Salmonella/microsome test adapted for volatile compounds. Linear dose-response relationships were obtained for supercritical CO2-extracted EDB using tester strain TA100 (+/- S9) and for 4-NB using tester strains TA98 and TA100 (-S9). Standard dose-response curves with known amounts of the compounds were also determined for comparison with measured amounts of the model compounds collected in an airstream. The gas chromatographic (GC)- and bioassay-determined quantities of EDB and 4-NB were highly correlated, accurate and precise. For example, bioassay-determined EDB concentrations were within 10% of the GC-determined concentrations. Our results demonstrate that the integrated methodology for vapor-phase mutagens developed in this study would be useful for quantitative analysis of these and related airborne vapor-phase mutagenic compounds.

Predicting pesticide emissions and downwind concentrations using correlations with estimated vapor pressures.

Pesticide emissions to air have been shown to correlate with compound vapor pressure values taken from the published literature. In the present study, emissions correlations based on vapor pressures derived from chemical property estimation methods are formulated and compared with correlations based on the literature data. Comparison was made by using the two types of correlations to estimate emission rates for five herbicides, a fungicide, and an insecticide, for which field-measured emission rates from treated soil, foliage, and water were available. In addition, downwind concentrations were estimated for two herbicides, three fungicides, four insecticides, and two fumigants, for which concentration measurements had been made near treated sources. The comparison results demonstrated that correlations based on vapor pressures derived from chemical property estimation methods were essentially equivalent to correlations based on literature data. The estimation approach for vapor pressures is a viable alternative to the inherently more subjective process of selecting literature values.

Integration of immunochemical methods with other analytical techniques for pesticide residue determination.

The growing volume of literature concerning immunoassay analysis for trace levels of agrochemicals and other low molecular weight contaminants in various matrixes is indicative of the tremendous interest in and utility of this analytical technique. Most immunoassay methods described in the literature analyze compounds directly, for example, a herbicide in water, or involve solvent exchange of an organic sample extract or dilution of an aqueous-based sample to minimize the matrix effect. As immunoassay for small molecules becomes widely accepted and applied, new challenges involving more complex chemicals in more difficult matrixes arise. The integration of "classical" analytical chemistry with immunochemistry can provide new techniques and approaches useful in discovering the movement, mode of action, and ultimate impact of certain chemicals on humans and the environment.

Loss of carbofuran from rice paddy water: chemical and physical factors.

The loss of carbofuran was studied from rice paddy water treated with a granular formulation of the insecticide, and from ponds filled with drainage from the paddy. The average half-life (t 1/2) for carbofuran loss was 57 hr. Controlled experiments indicated that pH was the predominating factor governing carbofuran loss from water in the environment studied. The loss due to hydrolysis was over 700 times more rapid at pH (t 1/2 = 1.2 hr.) than at pH (t 1/2 = 864 hr.) in buffered deionized water. The average pH of the rice paddy was 8, but diurnal fluctuations of 7 to 9.5 are common in similar environments. Impurities in the water, sunlight, and temperature influence the rate of carbofuran loss but not nearly so much as pH. There was no evidence for significant loss due to evaporation or oxidation. The results have important implications for the duration of the insecticide's activity and the effect on fish within or downstream from treated paddies.

A method for the trace analysis of naptalam (N-1-naphthylphthalamic acid) in water.

A method for the trace analysis of naptalam, N-1-naphthylphthalamic acid, in water is presented. Naptalam, a pre-emergent, broad-leaf, and grassy herbicide, is used with soybean, peanut, and vine crops. Tap and well water samples are extracted on a cyclohexyl solid phase extraction cartridge, eluted from the cartridge with methanol, and evaporated to dryness. The sample is esterified with diazoethane, evaporated to dryness, reconstituted with methanol, and converted to the stable N-1-naphthyl phthalimide in the gas chromatograph (GC) injector port for detection and quantitation using a nitrogen-phosphorus detector. Sample injection technique and injector port temperature are critical to high derivatization yields. Confirmation of conversion to N-1-naphthyl phthalimide was made by gas chromatograph/mass spectrometer (GC/MS). Spiking tests at levels of 3 to 100 micrograms/L showed good recovery.

Environmental activation of pesticides.

Spray drift from application sites, runoff from agricultural fields, leftover products from home use, and accidental spills have made pesticide contamination ubiquitous in the environment. As a pesticide moves through the environment, it may react through chemical and biotic processes such as hydrolysis, oxidation, or reduction, or be metabolized in microorganisms, animals, plants, and humans. Most reactions will be inactivations, forming degradation products less toxic or persistent than the parent compound. However, some reactions are activations, creating breakdown products equally or more toxic, persistent, or mobile than the parent and posing a greater threat to nontarget organisms and the environment. Examples are drawn from the major classes of pesticides including organochlorine compounds (DDT and aldrin), organophosphorus pesticides (malathion), carbamate pesticides (aldicarb), and fungicides to illustrate the various activation routes.

An analytical method for trifluoroacetic Acid in water and air samples using headspace gas chromatographic determination of the methyl ester.

An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials. Air samples are collected in sodium bicarbonate-glycerin-coated glass denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air. Several environmental air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA.

Comparison of extraction techniques, including supercritical fluid, high-pressure solvent, and soxhlet, for organophosphorus hydraulic fluids from soil.

The efficiencies of three extraction techniques for removal of nonpesticidal organophosphates from soil were determined. Traditional Soxhlet extraction was compared to supercritical fluid extraction (SFE) and a low solvent volume flow through technique referred to here as high-pressure solvent extraction (HPSE). SFE, optimized by varying parameters of temperature, pressure, and methanol polarity modifier, showed at least 90% efficiency in the extraction of OPs from both spiked and native soils. HPSE experiments showed efficient and consistent recoveries over a range of temperatures up to 200 °C and pressures up to 170 atm. Recovery of TCP from spiked soils with HPSE depends on the system variables of temperature and pressure, which dictate density and flow rate. HPSE provided extraction efficiencies comparable to those obtained with Soxhlet extraction and SFE but with substantial savings of time and cost.

Sampling and analysis of airborne residues of paraquat in treated cotton field environments.

A method was developed for the analysis of paraquat residues in airborne particulate matter collected by filtration or impaction. The method is based on extraction of paraquat with 6N hydrochloric acid, transfer of residue to saturated ammonium bicarbonate solution, and reduction of the resulting residue with alkaline sodium borohydride to a mixture of two tertiary amines with subsequent determination by nitrogen-selective gas chromatography (GLC). Recoveries ranged from 74 to 96% for filters spiked at 0.05 microgram and above; the limit of detection is approximately 0.5 ng/m3 for high volume air samples. Paraquat concentrations measured in the air downwind from two commercial applications to cotton during spraying fell regularly from extrapolated interval-average values of 4.31 and 10.7 microgram/m3 at the 1 m downwind edge of the two fields to less than 50 ng/m3 at approximately 400 m downwind. Downwind samples taken 2 to 4 hr after spraying contained 1 to 10% as much paraquat as those during spraying, and by 5 to 7 hr no paraquat was detectable in the downwind air. Paraquat was also found in the airborne particulate matter during mechanical harvesting of one of the fields, the maximum interval-average values being 1,245 and 516 ng/m3 just outside and inside an open cab, respectively. The analytical findings for paraquat are compared with those for S,S,S-tributylphosphorotrithioate (DEF), a component of the harvest aid mixture employed, and discussed in terms of occupational exposure, potential hazard, and recommended occupational practices.