Speciation analysis of arsenic compounds in edible oil by ion chromatography–inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic (IC) detector for the speciation analysis of arsenic in edible oil. The arsenic species studied include arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine. Gradient elution using (NH4)2CO3 and methanol at pH 8.5 allowed the chromatographic separation of all species in less than 8 min. Effluents from the IC column were delivered to the nebulizer of ICP-MS for the determination of arsenic. The concentrations of arsenic species have been determined in several used and fresh vegetable oil samples. In this study, a microwave-assisted extraction method was used for the extraction of arsenic species from oil samples. The extraction efficiency was better than 92% and the recoveries from spiked samples were in the range of 90–105%. The precision between sample replicates was better than 8% for all determinations. The limits of detection were in the range of 0.008–0.024 ng mL−1 for various arsenic species based on peak height, which corresponded to 0.08–0.24 ng g−1 in the original oil sample. The major arsenic species in the used oil samples varied based on the food items cooked.