Streamlined sample preparation procedure for determination of perchlorate anion in foods by ion chromatography-tandem mass spectrometry

A rapid, sensitive, and specific method was developed for the determination of perchlorate anion in foods. The foods included high moisture fruits and vegetables, low moisture foods (e.g. wheat flour and corn meal), and infant foods. Improvements to existing procedures were made in sample preparation that reduced sample test portion size from 100 to 5 or 10 g, extraction solvent volume from 150 to 20-40 ml, and replaced blending extraction-vacuum filtration and their associated large glassware with a simple shakeout-centrifugation in a small conical tube. Procedures common to all matrices involved: extraction, centrifugation, graphitized carbon solid phase extraction (SPE) cleanup, and ion chromatography-tandem mass spectrometry (IC-MS/MS) analysis. A Waters IC-Pak Anion HR column (4.6 mm × 75 mm) was eluted with 100 mM ammonium acetate in 50:50 (v/v) acetonitrile/water mobile phase at a rate of 0.35 ml/min. A triple stage quadrupole mass spectrometer, equipped with electrospray ionization (ESI) in the negative ion mode, was used to detect perchlorate anion. An ¹⁸O₄-labeled perchlorate anion internal standard was used to correct for any matrix effects. The method limit of quantitation (LOQ) was: 1.0 μg/kg in fruits, vegetables, and infant foods; 3.0 μg/kg in dry products. Fortified test portions gave 80-120% recoveries. Determination of incurred perchlorate anion residues agreed well with results for comparable commodities or products analyzed by published methods.