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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.

An analytical method for the determination of fenhexamid [N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide] in caneberry, blueberry, and pomegranate was developed utilizing acetone extraction, column cleanup, liquid-liquid partitioning, and liquid chromatography-tandem mass spectroscopy (LC-MS/MS) for detection. Method validation recoveries ranged from 91 to 96% for caneberry, from 80 to 91% for blueberry, and from 74 to 95% for pomegranate. Control samples collected from IR-4 trials for all matrixes had residue levels of0.020 ppm. Fenhexamid-treated field samples had residue levels that ranged from 0.46 to 16.11 ppm (caneberry), from 0.87 to 2.91 ppm (blueberry), and from 1.59 to 1.85 ppm (pomegranate). The method was validated to a limit of quantitation of 0.020 ppm, and the limit of detection was 0.009 ppm.

Methoxyfenozide [3-methoxy-2-methylbenzoic acid 2-(3,5-dimethylbenzoyl)-2-(1,1-dimethylethyl) hydrazide; RH-2485], in the formulation of INTREPID, was applied to various crops. Analysis of methoxyfenozide was accomplished by utilizing liquid-liquid extraction and partitioning, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method validations for fruits, vegetables, and mint are reported. Methoxyfenozide mean recoveries ranged from 72 to 129% over three levels of fortification. The overall average of mean recoveries is 97 +/- 10%. The limit of quantitation for fruits, artichoke, cucumber, squash, and refined sugar was 0.010 ppm, with a detection limit of 0.005 ppm. For all other crops, the limit of quantitation was 0.050 ppm, with a detection limit of 0.025 ppm. No residues were found greater than the limit of quantitation in control samples. Residues above the limit of quantitation were found in all matrices except refined sugar. Foliage (bean, beet, pea, and radish) had greater residue levels of methoxyfenozide residue than their corresponding roots or pods. Other crop matrices contained

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.