Abstract

A column-switching system between a cation-exchange column (PRP-X200) and an anion-exchange column (PRP-X100) was used for separation of eight arsenic species. The sample was injected on the PRP-X200 column and the species eluted in the void volume of that column [arsenite (As^III), arsenate (As^V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine (AB)] were transferred to the PRP-X100 column and, after separation, were thermo-oxidized on-line and detected by hydride generation (HG) atomic absorption spectrometry (AAS). The species initially retained in the PRP-X200 column were subsequently separated in that column, thermo-oxidized on-line and detected by HG atomic fluorescence spectrometry (AFS). The organoarsenical species present in natural seafood products were extracted with methanol–water and quantified using the proposed method. The analytical features of the method are reported. The highest limit of detection (LOD) for the sample was obtained for AB [3.6 ng g⁻¹, dry mass (dm)], whereas TMAO and DMA gave the lowest LOD (0.9 ng g⁻¹ dm). For all species the methodology developed provides optimum precision, ranging from 1 to 12%, and the recovery percentage was greater than 95% for all species. The method was applied to the following certified reference materials: CRM 627 (Tuna fish tissue, Institute for Reference Materials and Measurements, IRMM), DORM-2 (Dogfish muscle, National Research Council of Canada, NRCC), TORT-2 (Lobster hepatopancreas, NRCC) and NFA-Shrimp and NFA-Plaice (National Food Agency of Denmark). Only CRM 627 is certified for arsenic species (AB and DMA), and the contents obtained for these species were compared with the certified values. The contents of the other arsenic species present in CRM 627 and the species in the other reference materials were compared with the data reported by other authors.