Isotope dilution-gas chromatography/mass spectrometry method for the analysis of alkylphenols, bisphenol A, and estrogens in food crops.

A gas chromatography/mass spectrometry (GC/MS)-based isotope dilution technique was developed for determination of environmental estrogens in vegetables and fruits. The isotopically labeled standards of related environmental estrogens were used as the isotope dilution standards (IDS) to form the following analyte/surrogate pairings: octylphenol/(13)C6-4-n-nonylphenol, 4-n-nonylphenol/(13)C6-4-n-nonylphenol, 4-nonylphenol/(13)C6-4-n-nonylphenol, bisphenol A/(13)C12-bisphenol A, estrone/(13)C6-estrone, 17-α-estradiol/(13)C6-β-estradiol, 17-β-estradiol/(13)C6-β-estradiol, 17-α-ethynylestradiol/(13)C2-17-α-ethynylestradiol, and estriol/D4-estriol. Plant samples were homogenized and extracted ultrasonically with acetone. Acid pretreatment greatly increased peak intensities for the analytes. Acid hydrolysis pretreatment was important for liberating conjugates of estrogenic contaminants in plant materials. Recoveries of the spiked analytes were greater than 90%. Method limits of detection (LOD) ranged from 0.01 to 0.20 μg kg(-1) while limits of quantification (LOQ) ranged from 0.04 to 0.60 μg kg(-1). Bisphenol, nonylphenol, and natural estrogens were detected in vegetable and fruit samples obtained from local markets, illustrating the feasibility of this method for determining trace estrogenic contaminants in vegetables and fruits. The method has significant environmental implications in terms of the simultaneous analysis of estrogenic contaminants in vegetables and fruit.