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This chapter provides a review of the most current chromatographic methods available for the analysis of carbamate insecticides. Gas chromatography (GC)/mass spectrometry has been used as a confirmation procedure for insecticidal carbamates, particularly supporting multiresidue pesticide screening methods. Sensitive analytical methods for the detection of insecticidal carbamate residues include the use of thin-layer chromatography, GC, high performance liquid chromatography, gas chromatography-mass spectrometry, and liquid chromatography-mass spectrometry. Thin-layer chromatography is a useful qualitative and quantitative tool for analysis of carbamate insecticides, which may not be as amenable to GC analysis due to lack of thermostability. High-performance liquid chromatography methods for analysis of carbamate insecticides are often the preferred methods for these thermally labile compounds. Liquid chromatography with mass spectrometric detection has been widely accepted as the preferred technique for the identification and quantification of polar and thermally labile compounds such as insecticidal carbamates.

Pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine], in the formulation of Prowl (a commercial herbicide), was applied to various crops. Analysis of pendimethalin and its metabolite [4(1-ethylpropyl)amino-2-methyl-3,5-dinitrobenzyl alcohol] was accomplished by utilizing liquid-liquid partitioning, gel permeation chromatography (GPC) for nuts and mint, solid-phase extraction (SPE) cleanup, and gas chromatography (GC) with a nitrogen--phosphorus detector (NPD). Method validation recoveries for fruits, nuts, vegetables, grass, and mint are given for both compounds. Pendimethalin average recoveries ranged from 71% to 126% over two levels of fortification. Pendimethalin metabolite average recoveries ranged from 69% to 123% over two levels of fortification. The quantitation limit for all crops except mint was 0.050 ppm. The quantitation limit for mint and mint oil was 0.10 ppm. Residues greater than the limit of quantitation were found for pendimethalin in apple pomace, fresh and dry fig, grass screenings, mint oil, almond hulls, green onion, and tomato pomace (wet and dry). Residues greater than the limit of quantitation were found for pendimethalin metabolite in grass screenings, grass straw, and almond hulls. All other crop analyses for pendimethalin and its metabolite were below the limit of quantitation.