EXTRACTION, CLEANUP AND LIQUID CHROMATOGRAPHIC-DIODE ARRAY DETERMINATION OF CARBAMATE PESTICIDES IN SOIL SAMPLES

Significant analytical problems occur during the isolation and assay of carbamate insecticide residues in soils. Nonetheless, liquid-chromatographic diode array can be used to measure species concentrations (e.g., carbofuran, chlorpropham, carbaryl, propoxur, pirimicarb, and oxamyl) in the low ppm range. Low concentrations of the soil-matrix breakdown product, 1-naphthol, can also be measured. Several different extraction mixtures (e.g., acetone-ethyl acetate, acetone-dichloromethane, acetone-methanol, and methanol alone) are compared. Cleanup procedures use Florisil column chromatography and several eluents, mixtures of acetone and dichloromethane. Aminopropylsilica and Florisil cartridges give promising results for routine analyses. Diode array detection is useful for obtaining UV-spectral information of matrix interferences and blanks. Co-eluted peaks may be differentiated using the second derivatives of spectra. The methodology is validated by analyzing residue levels of pirimicarb in real soil samples at the 0.1-mu-g/g level.