Determination of Inorganic Arsenic in Fish Oil and Fish Oil Capsules by LC-ICP-MS

Abstract

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.

Method: 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 (LC) inductively coupled plasma (ICP) MS using an octadecylsilane (ODS) column with a mobile phase containing an ion-pair reagent.

Results: The LOD (0.005, 0.004 mg/kg), LOQ (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. A low level of inorganic arsenic was detected only in anchovy oil among all fish oil samples that were 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: Arsenic speciation in fish oil and fish oil capsules was analyzed by LC-ICP-MS using an ODS column with a mobile phase containing an ion-pair reagent. A low level of inorganic arsenic was detected only in anchovy oil. No inorganic arsenic was detected in fish oil capsules.