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

Soxhlet extraction has been compared to sonication and microwave assisted extraction of arsenite, arsenate, dimethylarsenic, monomethylarsenic and arsenobetaine from biota samples (oyster, cockle, mussel and fresh water alga) and Certified Reference Materials TORT-1 and CRM 627, using methanol and methanol-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 of 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 superior to the other clean-up procedures. Recoveries higher than 71% were obtained depending on the type of sample. An unknown compound was found to be the main arsenic species in the marine samples.