Determining multifumigants in whole grains and legumes, milled and low-fat grain products, spices, citrus fruit, and beverages

Abstract

Whole grain and legumes, milled and low-fat products, spices, citrus fruit, and dry beverage ingredients are leached with purified, acidified acetone-water solutions. Portions of these leachates are then back-extracted with purified isooctane. Liquid beverages are directly extracted with the isooctane. Six to 10 microL of each isooctane extract is then screened for 11 fumigant residues by gas chromatography (GC) using electron-capture and Hall electroconductivity detectors, and dual 20% OV-101 columns. Further confirmation of residue identity is done on 20% OV-225/20% OV-17 (2.5 + 1 mixed-bed) and 10% SP-1000 columns. The analytes determined include methyl bromide, methylene chloride, carbon disulfide, chloroform, ethylene dichloride, methyl chloroform, carbon tetrachloride, trichloroethylene, chloropicrin, ethylene dibromide, and tetrachloroethylene, using mixed-component reference solutions. Average recoveries from fortified grain range from 25 to 85%; methyl bromide and chloropicrin were recovered the least. Recoveries from the other kinds of food samples range from 43 to 111%. Advantages of this procedure are (1) clean sample extracts, (2) ppb detection limits, (3) residue stability, (4) relative speed, quality control, and safety of the analysis, and (5) results which gave an accurate picture of residual fumigants in grain and food products.