FLOW-INJECTION SORBENT EXTRACTION WITH DIALKYLDITHIOPHOSPHATES AS CHELATING AGENT FOR NICKEL, COBALT AND MANGANESE DETERMINATION BY ATOMIC-ABSORPTION SPECTROMETRY

Using octadecyl functional group (C-18) bonded silica gel as sorbent a nd methanol or ethanol as eluent, the extractability of nickel, cobalt and manganese with diethyl-, di-n-propyl-, di-2-propyl-, di-n-butyl-, di-isobutyl-, di-2-butyl-, di-n-pentyl- and di-n-hexyldithiophosphate s, (RO)(2)P(SS-, was investigated in respect of the effects of pH, alk yl substituent group, reagent concentration and masking agent by flame atomic absorption spectrometry. The extractability increases with the chain length of the substituent groups in the reagents and is quantit ative for alkyl groups larger than butyl at pH ca. 3. At a high concen tration of di-n-pentyldithiophosphate, the metals are selectively extr acted from coexisting cadmium, copper, lead and iron. As an analytical demonstration, di-n-pentyldithiophosphate was used for the determinat ion of ultra-trace concentrations of nickel in two certified reference saline water samples (sea water and estuarine water) by graphite furn ace atomic absorption spectrometry. Results were in good agreement wit h the certified values. The detection limit (3 sigma) of peak area mea surement was 0.07 mu g l(-1) with an enrichment factor of 10 for nicke l with 20-s sample loading at 8.7 ml min(-1) and 20-mu l eluate inject ion.