No abstract

A multiresidue method using supercritical fluid ex-traction (SFE) and gas chromatography/ion trap mass spectrometry (GC/1TMS) was developed for analysis of 46 pesticides in fruits and vegetables. The SFE procedure used 2 commercial instruments that trapped the extracts on solid-phase material. Silica gel chemically bound to octadecylsi-lane (ODS) collected the extracted pesticides efficiently, and elution of the trap with acetonitrile gave high recoveries. Extracts thus obtained were sufficiently clean for subsequent GC/ITMS analysis. The SFE conditions were 320 atm and 60°C (0.85 g/mL CO2 density) and 1.6 mL/min CO2 flow rate for 6 extraction vessel volumes. Trapping on 1 mL ODS occurred at 10°C, and a 0.4 mL/min flow rate of acetonitrile at 40°–50°C was used to elute the pesticides. Quantitative and qualitative analyses of the 46 pesticides were performed simultaneously by GC/ITMS. Studies of fortified samples gave >80% recoveries for 39 pesticides, and recoveries of >50% for the other pesticides, except methamidophos and omethoate. Grapes, carrots, potatoes, and broccoli were used as samples during method development, and a blind experiment involving incurred and fortified samples was used to test the approach. Results of the blind study compared satisfactorily with results from 7 laboratories using traditional GC detectors and solvent-based extractions.

Conventional extraction procedures with acetonitrile were compared with supercritical fluid extraction (SFE) with CO2 for determining 10 pyrethroids in fortified lettuce and meat samples. Because SFE utilized a minimal cleanup procedure, nonvolatiles may accumulate on the capillary column in both the gas chromatography-ion trap mass spectrometry (GC-ITMS) and electron capture (EC) detection modes shortening the lifetime of the columns after multiple injections. The GC-ITMS method proved satisfactory for analysis of lettuce whereas EC-GC proved more suitable for residue analysis of meat samples. Improvements in multiresidue methods for monitoring of synthetic pyrethroids in raw agricultural commodities should aid in registration and reregistration activities. Keywords: SFE; insecticides; meat; fat; ion-trap