In-house validation of chromatographic speciation methods for arsenic in fishery products

The relatively high concentrations of arsenic found in shellfish in recent years have contributed to raise the threshold of attention of European Union, in terms of food security. Among the various factors that influence the toxicity of arsenic, the chemical form is of particular significance, given the high toxicity of the inorganic form in respect of the organic that frequently contaminates fishery products. The Expert Committee of FAO / WHO defined a provisional tolerable weekly intake (PTWI) of 15 mg/kg b.w. only for the inorganic form and, in view of definition of residual limits for arsenic in fish, it becomes necessary to have analytical methods able to differentiate inorganic form from the organic ones (e.g. monomethyland dimethylarsenic acid, arsenobetaine, arsenocholine). The purpose of this study was to optimize and validate an analytical method for the speciation of arsenic in fishery products, that could identify and quantify the organic forms of arsenic. Screening of organic forms of arsenic was carried out using HPLC (high performance liquid chromatography) coupled to a tandem mass spectrometry detector, while determination of total arsenic was carried out using the atomic absorption spectroscopy. The validation procedure was conducted according to the requirements of the European Community to allow the use of the present method by the Official Control laboratories. The matrices considered for method optimization and validation have been fish, molluscs and crustaceans from the coasts of southern Italy. Obtained results allowed the method to enter within the routinely activities of the laboratory and require method accreditation.