FLOW-INJECTION SORBENT EXTRACTION WITH DIALKYLDITHIOPHOSPHATES AS CHELATING AGENT FOR THE DETERMINATION OF ZINC BY FLAME ATOMIC-ABSORPTION SPECTROMETRY

Dialkyldithiophosphates, (RO)(2)P(SS-, were used as the complexing age nt for flow injection on-line sorbent extraction for the determination of zinc by name atomic absorption spectrometry. The extractability,wi th diethyl-, di-n-propyl-, di-2-propyl-, di-n-butyl-, di-isobutyl-, di -sec.-butyl-, di-n-pentyl- and di-n-hexyldithiophosphates was compared in respect of the effects of pH, alkyl group, masking agent and reage nt concentration. Di-sec-butyldithiophosphate (0.5%, m/v) at pH 3 with 0.1 M citrate as a masking agent for iron, was used for the determina tion of zinc in a number of certified biological and environmental ref erence materials from the Community Bureau of Reference (BCR). All ana lytical results were in good agreement with the certified values. The detection limit (3 sigma) of peak height measurement, using a flow spo iler in the spray chamber, was 0.5 mu g l(-1) with an enhancement fact or of 35 for a 20-s sample loading at 8.7 ml min(-1).