Selective extraction of iron oxide associated arsenic species from sediments for speciation with coupled HPLC-HG-AAS

A procedure for the extraction of arsenic species from estuarine iron oxide rich sediments was developed based on the use of hydroxylammonium hydrochl oride solution as leaching agent. Different variables such as extractant vo lume, concentration and time of extraction were used. Optimum conditions we re obtained by using 40 ml of 0.4 M hydroxylammonium hydrochloride for 8 h at 95 degrees C with occasional shaking. Speciation of arsenic was performe d with coupled HPLC-HG-AAS, using a strong anion-exchange column for the se paration of arsenite, dimethylarsinic acid, monomethylarsonic acid and arse nate. The influence of the concentration of the extractant on the chromatog raphic separation was also studied. Complete recoveries of arsenic species required several repetitive extractions. Results obtained for CRM 320 River Sediment, certified for total arsenic concentration, were low, which indic ated the influence of the matrix composition on the final extraction.