Determination of inorganic arsenic in fish oil and fish oil capsules by LC-ICP-MS.

BACKGROUND As inorganic arsenic is a highly toxic compound, its concentration in foods should be determined. OBJECTIVE Develop an analytical method for determining inorganic arsenic in fish oil and fish oil capsules. METHODS Inorganic arsenic was extracted from fish oil by heating at 80 °C in 1.6% tetramethylammonium hydroxide-ethanol. The concentration of inorganic arsenic in fish oil was determined by liquid chromatography-inductively coupled plasma-mass spectrometry using an ODS column with a mobile phase containing an ion-pair reagent. RESULTS The limits of detection (0.005, 0.004 mg/kg), limits of quantitation (0.016, 0.011 mg/kg), repeatability (4.2, 3.5%), intermediate precision (5.4, 3.5%), and trueness (recoveries 94-109% based on spiked samples) of the proposed method were satisfactory for inorganic arsenic in fish oil and fish oil capsules. Low level of inorganic arsenic was detected only in anchovy oil among all fish oil samples we used in this study. Inorganic arsenic levels were below the quantitation limit in all fish oil capsules. CONCLUSIONS Inorganic arsenic was determined after extraction from fish oil by heating at 80 °C in 1.6% tetramethylammonium hydroxide-ethanol. The level of inorganic arsenic in all fish oil samples examined in this study was lower than 0.1 mg/kg of the maximum level defined in the Codex. HIGHLIGHTS