Metal ion binding by algae and its novel electroanalytical applications

Several inactivated algal species have been screened for their aluminum(III), copper(II), and tetrachloroaurate(III) binding characteristics. All algal species tested were found to adsorb these three metal ions, although the pH dependences, and binding capacities differed amongst certain species. Based on the ability of algae to trap metal ions from dilute solutions and the different affinities of metal ions for algal surfaces, novel types of electroanalytical sensors were developed.;Eight different algal species were found to bind aluminum(III) and copper(II) in a pH-dependent manner, and decreased metal binding occurred as the pH was lowered from 5 to 2. However, the binding of gold(III) to most of these algae was relatively independent of pH.;The algae screened were found to bind more gold(III) than aluminum(III) and copper(II). Chlorella pyrenoidosa was determined to have the highest gold(III) binding capacity. However, Eisenia bicyclis was found to possess the largest aluminum(III) and copper(II) binding capacities. Gold(III) binding by the algae was effectively reversed by acidic thiourea solutions. On the other hand, binding of aluminum(III) and copper(II) to the algae was efficiently reversed by 1 N sulfuric acid solutions.;Sequential metal ion separations were accomplished without a change in solution pH. The sequential binding of gold(III) and aluminum(III), respectively, occurred at pH 2.0 when the metal solution was exposed first to Chlorella pyrenoidosa and then to Eisenia bicyclis. Another separation scheme involved the sequential binding of gold(III) and copper(II) from a solution at pH 2.0 to Spirulina platensis and Cyanidium caldarium, respectively.;Novel algae-modified electrodes for the quantification of copper(II) and gold(III) were developed. The Eisenia bicyclis-modified electrode was found to be a good copper(II) analytical sensor. Rapid and convenient acid renewal allowed use of a single modified electrode in multiple analytical determinations. On the other hand, the high capacity of Chlorella pyrenoidosa for gold(III) ions was used to make an efficient alga-modified electrode. Besides potential analytical applications, performance of such an electrode provided valuable insights into the interaction of gold(III) ions with the Chlorella algal cells.