Multiresidue analysis of 102 organophosphorus pesticides in produce at parts-per-billion levels using a modified QuEChERS method and gas chromatography with pulsed flame photometric detection.

A multiresidue method for the analysis of organophosphorus pesticides in fresh produce at levels down to 1.0 microg/kg (ppb) has been developed using a modification of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. The procedure entails extraction of pesticides from the sample with acetonitrile, salting-out with magnesium sulfate (MgSO4) and sodium chloride, and cleanup of the resulting extracts with dispersive solid-phase extraction using primary-secondary amine, graphitized carbon black, and MgSO4. Fortification studies were performed for 102 organophosphorus pesticides at 1.0, 10, and 100 ppb in 4 different pesticide-free commodities (grape, orange, spinach, and tomato). Recoveries ranged from 63-125%, with >80% being achieved for most of the pesticides tested in each commodity. The procedure was applied to the analysis of 400 produce samples collected from a cohort of children that participated in the Children's Pesticide Exposure Study and the Longitudinal Dietary Pesticide Exposure Study in which selected 24 h duplicate food items were collected throughout a 12-month period. Residues of 15 of the 102 pesticides were detected at levels ranging from <1 to 526 ppb.

Single-laboratory validation of a method for the determination of furan in foods by using headspace gas chromatography/ mass spectrometry, part 2--low-moisture snack foods.

In 2004, a quantitative headspace (HS) gas chromatographic/mass spectrometric method was developed and used to determine furan in approximately 300 foods. This method was modified and validated for the determination of furan in low-moisture snack foods. The modifications include a smaller test portion size and lower HS oven temperature. The limits of detection ranged from 0.4 ng/g in graham crackers to 4.4 ng/g in pretzels. Recoveries from samples fortified at 0.5, 1,2, and 3 times the levels of incurred furan found in the samples ranged from 96 to 102%, and HorRat values showed that the recovery data met the criteria for repeatability. The modified method was shown to be reliable for the determination of furan in foods when test portions were equilibrated for 30 min in a 60 degrees C HS oven. The modified method was used to conduct a survey of furan in 22 low-moisture snack foods. All of the samples were found to contain furan ranging from 3.7 ng/g in graham crackers to 60 ng/g in corn chips. Results from the survey were consistent with results obtained for similar snack foods analyzed by a U.S. Food and Drug Administration field laboratory.