Simplified multiresidue method for liquid chromatographic determination of N-methyl carbamate insecticides in fruits and vegetables.
A simplified method is described for determining 7 N-methyl carbamates (aldicarb, carbaryl, carbofuran, methiocarb, methomyl, oxamyl, and propoxur) and 3 related metabolites (aldicarb sulfoxide, aldicarb sulfone, and 3-hydroxy carbofuran) in fruits and vegetables. Residues are extracted from crops with methanol; coextractives are then separated by gel permeation chromatography (GPC) or GPC with on-line Nuchar-Celite cleanup for crops with high chlorophyll and/or carotene content (e.g., cabbage and broccoli). Carbamates are separated on a reverse-phase liquid chromatography column, using a methanol-water gradient mobile phase. Separation is followed by postcolumn hydrolysis to yield methylamine, and the formation of a fluorophore with o-phthalaldehyde and 2-mercaptoethanol prior to fluorescence detection. Recovery data were obtained by fortifying 5 different crops (apples, broccoli, cabbages, cauliflower, and potatoes) at 0.05 and 0.5 ppm. Recoveries averaged 93% at both fortification levels except for the very polar aldicarb sulfoxide for which recoveries averaged around 52% at both levels. The coefficient of variation of the method at both levels is less than 5% and the limit of detection, defined at 5 times baseline noise, varies between 5 and 10 ppb, depending on the compound.
Chaput
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Agriculture Canada, Laboratory Services Division, Ottawa, Ontario.
D002219:Carbamates; D002850:Chromatography, Gel; D002853:Chromatography, Liquid; D005638:Fruit / Q000032:analysis*; D007202:Indicators and Reagents; D007306:Insecticides / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D014675:Vegetables / Q000032:analysis*
D002219:Carbamates; D007202:Indicators and Reagents; D007306:Insecticides; D010573:Pesticide Residues