Speciation and preconcentration of trace elements with immobilized algae for atomic absorption spectrophotometric detection

Abstract

The properties of two covalently immobilized algae, Chlamydomonus reinhartii and Selenestrum capricornutum, were compared for the preconcentration of Cu²⁺, Ag⁺, Cr³⁺ and Cr⁶⁺. These reagents were found to have different properties, with Chlamydomonus reinhartii having a lower capacity for Cu²⁺ and a higher capacity for Cr⁶⁺ With the exception of Cr⁶⁺, the maximum preconcentration of the metal ions investigated occurred at different pH values for the different algae, suggesting that different binding sites were involved. The accuracy of the preconcentration method for the analysis of estuarine sediment (using both reagents) 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 interference occurred between the two species. Further interference studies showed that metal ion interferences were minor even when the interfering ion was present in excess. The effects of sodium chloride, sodium hydrogencarbonate and humic acid were also studied and these were found to interfere by competing for the metal ions to be complexed.