SPECIATION AND PRECONCENTRATION OF TRACE-ELEMENTS WITH IMMOBILIZED ALGAE FOR ATOMIC-ABSORPTION SPECTROPHOTOMETRIC DETECTION

The properties of two covalently immobilized algae, Chlamydomonus rein hartii and Selenestrum capricornutum, were compared for the preconcent ration of Cu2+, Ag+, Cr3+ and Cr6+. These reagents were found to have different properties, with Chlamydomonus reinhartii having a lower cap acity for CU2 + and a higher capacity for Cr6+. With the exception of Cr6+, the maximum preconcentration of the metal ions investigated occu rred at different pH values for the different algae, suggesting that d ifferent binding sites were involved. The accuracy of the preconcentra tion method for the analysis of estuarine sediment (using both reagent s) was illustrated with a reference sample obtained from the National Research Council Canada. A flow system for the speciation of Cr6+ and Cr3+ was then developed using both reagents. It was shown that no inte rference occurred between the two species. Further interference studie s showed that metal ion interferences were minor even when the interfe ring ion was present in excess. The effects of sodium chloride, sodium hydrogencarbonate and humic acid were also studied and these were fou nd to interfere by competing for the metal ions to be complexed.