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
Monitoring results of food grain contamination with fusariotoxins-deoxynivalenol (DON), zearalenone (ZEN), fumonisins (FB1&FB2), T-2 and HT-2 toxins-are presented. Harvests of 2005-2010 in different regions of Russia were investigated. The occurrence of DON in wheat was 8%, barley 9%, oats 4%, rye 2% and maize 2%. The highest frequency of ZEN contamination was found in oats, the lowest in wheat. Calculated average daily intake of DON varied from 0.066 to 0.096 µg/kg body weight, the highest being found in the Southern region, but substantially lower than the provisional maximum tolerable daily intake. The results of enzyme-linked immunosorbent assay and high-performance liquid chromatography-mass spectrometry analysis demonstrated the presence of T-2 toxin in 14% and HT-2 toxin in 17% of all samples. The maximum level of T-2 toxin was exceeded only in one sample of barley. Relatively high frequency and levels of FB1&FB2 contamination were found in maize.
The simultaneous extraction of relatively polar and nonpolar pesticides has been problematic in multiresidue analysis using supercritical fluid extraction (SFE) with carbon dioxide. In fruit and vegetable samples, which typically contain 80-95% water, moisture acts to increase SFE recoveries of many polar pesticides, but a drying agent should be used to control water in SFE. Hydromatrix, a prevalent drying agent, has many desirable characteristics, but it reduces recovery of certain important pesticides, such as methamidophos, acephate, and omethoate. MgSO 4 has been shown previously to be applicable for the extraction of methamidophos and six other pesticides, but MgSO 4 has practical disadvantages in its use. In this study, properties and SFE results with the individual drying agents and their combination were evaluated. Simultaneous recoveries for polar and nonpolar pesticides were achieved for 71 pesticides fortified in apple using a mixture of 2 + 1 + 2 MgSO 4 •H 2 O-Hydromatrix-sample for extraction. The advantages of each drying agent were maintained by their combination. The analysis of real samples, however, showed that more study was needed to improve recoveries of nonpolar pesticides.
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