Characterization of National Food Agency Shrimp and Plaice Reference Materials for Trace Elements and Arsenic Species by Atomic and Mass Spectrometric Techniques

Abstract

The National Food Agency (NFA) of Denmark has produced and characterized NFA Plaice and NFA Shrimp reference materials (RMs) for the control of the accuracy of trace element and arsenic species determinations in similar seafood samples. The physical preparation of the materials included dissection, drying, milling and sieving to collect the fraction of particles less than 150 µm in size. In this fraction the trace elements were homogeneously distributed using a 400 mg sample intake for analysis. The total trace element concentrations were determined by graphite furnace and cold vapour atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS) and isotope dilution ICP-MS. The contents of arsenobetaine and the tetramethylarsonium ion were determined by cation exchange high performance liquid chromatography (HPLC) coupled with ICP-MS, or coupled with ion-spray (IS) tandem mass spectrometry (MS/MS) for qualitative verification. Based on a rigorous statistical analysis of the analytical data using the DANREF software, it was decided to assign certified values for mercury, cadmium and arsenic in the NFA Shrimp, and mercury, selenium and arsenic in the NFA Plaice. Indicative values were given for selenium, lead and chromium in the NFA Shrimp, and arsenobetaine and the tetramethylarsonium ion in both RMs. It is recommended that the certified mean value and the standard deviation of the distribution of means are used to construct Shewhart control charts ( x -charts) in order to evaluate the accuracy of a single as well as multiple determinations of a certified value in the RMs.