Ionic imprinted polymer solid-phase extraction for inorganic arsenic selective pre-concentration in fishery products before high-performance liquid chromatography - inductively coupled plasma-mass spectrometry speciation.

Low levels of inorganic arsenic [As(III) and As(V)] in fishery products have been selectively isolated from fish extracts (1.0 g of wet fish samples pre-treated with 10 mL of 1:1 methanol/water under sonication at 25 °C for 30 min) by ionic imprinted polymer (IIPs) based solid phase extraction procedure (on-column mode). The selective adsorbent was synthesized using sodium (meta) arsenite as a template, 1-vinyl imidazole as a functional monomer, divinylbenzene as a cross-linker, and 2,2'-azobisisobutyronitrile as an initiator. Optimized pre-concentration conditions imply fish extract (10 mL) pH adjustment at 8.5 before loading (flow rate of 0.25 mL min-1), and elution with ultrapure water (2 mL) at 0.50 mL min-1. A pre-concentration factor of 50 was finally obtained after evaporation to dryness (N2 stream) and re-dissolution in 0.2 mL of ultrapure water before HPLC-ICP-MS. Synthesized material was found to pre-concentrate inorganic arsenic species; whereas organic arsenic compounds, mainly arsenobetaine (the major organoarsenic compound in fish/seafood products), were not found to interact with the adsorbent. The developed selective method gave limits of quantification of 1.05 and 1.31 µg kg-1 for As (III) and As (V), respectively, and good precision [relative standard deviations lower than 12% in fish extracts spiked at several As (III) and As (V) levels]. The proposed method was finally applied to the selective determination of As (III) and As (V) species in several fishery products.