Evaluation of electrochemical hydride generation for the determination of arsenic and selenium in sea water by graphite furnace atomic absorption with in situ concentration

A continuous flow electrochemical hydride generation technique coupled with in situ concentration in a graphite furnace has been developed for determination of As and Se in seawater. Lead is used as cathode material for the production of arsine and hydrogen selenide. The efficiency of generation of arsine from As(III) is 86 +/- 6%, that from As(V) ranges from 73% to 86%. The efficiency of generation of hydrogen selenide from Se(IV) is 60 +/- 5% and from Se(VI) is 30 +/- 5%. The hydrides are trapped in an iridium-palladium coated graphite furnace prior to atomization. Absolute detection limits and concentration detection limits of 84 pg (3s(blank)) and 84 pg ml(-1) for determination of As using 1 ml sample volume and 75 pg (3s(blank)) and 7.5 pg ml(-1) for determination of Se using 10 ml sample volumes are obtained, respectively. The precision of replicate measurement for the analysis of reference materials at the 1.3 mu g l(-1) level for As(III) (0.8 ng absolute mass level) and at the 0.042 mu g l(-1) level for Se(IV) (0.42 ng absolute mass level) is better than 4% and 23% (relative standard deviation, RSD), respectively. The RSD values quoted above for Se include errors introduced by the sample preparation procedure.