Multi-class multi-residue analysis of pesticides in edible oils by gas chromatography-tandem mass spectrometry using liquid-liquid extraction and enhanced matrix removal lipid cartridge cleanup.

This study presents the development and validation of a method for the multi-class multi-residue analysis of pesticide residues in edible oils using liquid-liquid extraction followed by EMR-Lipid (enhanced matrix removal - lipid) cartridge cleanup, and then analyzed by gas chromatography tandem mass spectrometer (GC-MS/MS). The method was optimized for analyte recovery, matrix removal, and water removal during the sample extraction, sample cleanup and sample drying steps. The extraction efficiency of lipophilic pesticides (i.e. organochlorine) from the hydrophobic oil matrix was improved using a two-step liquid-liquid extraction with a mixture of ethyl acetate and acetonitrile. EMR-Lipid cartridges provided efficient and selective cleanup of the tested oil matrices. The developed method was verified by analyzing four edible oil matrices: olive oil, corn oil, soybean oil and canola oil. The results demonstrated that the method effectively removes unwanted matrix co-extractives better than conventional PSA/C18 dispersive solid phase extraction (dSPE) cleanup, while still delivering acceptable recovery results (recoveries of 60-120%) for the majority of pesticides tested. With the established quantification method, over 95% of the pesticides obtained for 70-120% accuracy, RSD < 20%, and calibration curves from 1 to 500 (400) ng/g in oil with R2 > 0.99.

Extraction of amphetamine and methamphetamine from urine specimens with Cerex Polycrom Clin II solid-phase extraction columns and the Speedisk 48 Pressure Processor.

Extraction of amphetamine and methamphetamine in urine was investigated using Cerex Polycrom Clin II solid-phase extraction columns and the Speedisk 48 Pressure Processor as a replacement for our liquid-liquid procedure. Linearity for urine standards extracted with the Cerex-Speedisk method ranged from 50 ng/mL for methamphetamine and from 150 ng/mL for amphetamine to 10,000 ng/mL for both. The mean recovery at the 500-ng/mL cutoff for three different lots of columns was 96.4% for AMP and 95.7% for MET. The mean of the within-run means for three batches was 495.4 ng/mL with a coefficient of variation (CV) of 1.2% or less for amphetamine and 496.4 ng/mL for methamphetamine with a CV of 1.7% or less. Thirty-six specimens containing amphetamine and the same number for methamphetamine were analyzed by both the Cerex-Speedisk and liquid-liquid methods. The correlation for specimens containing amphetamine gave an r2 of 0.9986 with a slope of 0.99; for methamphetamine, the r2 was 0.9997 with a slope of 0.98. The Cerex-Speedisk method cut extraction time in half, was less costly, and greatly reduced the volume of hazardous waste.