Comparison of biota sample pretreatments for arsenic speciation with coupled HPLC-HG-ICP-MS

Soxhlet extraction has been compared to sonication and microwave assisted e xtraction of arsenite, arsenate, dimethylarsenic, monomethylarsenic and ars enobetaine from biota samples (oyster, cockle, mussel and fresh water alga) and Certified Reference Materials TORT-1 and CRM 627, using methanol and m ethanol-water mixtures. A clean-up procedure using hexane partitioning was compared to the use of 0.45 mu m filter membranes, ultrafiltration (10 kDa) and C-18 cartridges. Measurements were carried out using coupled HPLC-(UV) -HG-ICP-MS. The best results were obtained for Soxhlet extraction (150 ml o f a (1:1) methanol-water mixture for 16 h) compared to both sonication (20 ml of methanol or methanol-water mixtures (1:3), (1:1) and (3:1) during 20 min) and microwave (20 ml of methanol or methanol-water mixtures (1:3), (1: 1) and (3:1) during 10 min at 150 W). Hexane partitioning was found to be s uperior to the other clean-up procedures. Recoveries higher than 71% were o btained depending on the type of sample. An unknown compound was found to b e the main arsenic species in the marine samples.