SEPARATION AND SPECIATION OF INORGANIC AND METHYLARSENIC COMPOUNDS INMARINE SAMPLES

A combination of an extraction and two-step ion-exchange process has b een developed for the separation and speciation of As(III), As(V) and their methylated forms mono-(MMA) and dimethylarsenic acid (DMA) at tr ace levels in marine samples. As(III) was first separated from all inv estigated As-compounds by extraction with ammonium pyrrolidinedithioca rbamate (APDC) into isobutylmethylketone (IBMK) at pH = 2 and determin ed after backstripping with HCl (1:1) by hydride-generation AAS. The r emaining As species were passed through the cation exchange resin Dowe x 50W-X8, where DMA was quantitatively retained As(V) and MMA, present in the effluent, were subsequently fixed in the anion exchanger AG1-X 8. Experimental conditions, including pH of the sample solutions and c ompeting ions were studied in order to achieve quantitative retention of these As compounds. By sequential elution, a good separation of the individual As species was obtained. The As concentration in each frac tion as well as total arsenic were determined by the hydride generatio n AAS technique. The developed process has been applied to the analysi s of simulated synthetic As mixtures obtained from BCR and of real mar ine samples.