A New Method for the Measurement of Complexing Capacity of Natural Water Using Gel Chromatography

Abstract

The mixture of sample and Cu²⁺ solutions was chromatographed with a Sephadex G-10 gel column using O.1 M (1 M=1 mol. dm^-3) Tris-HCl solution (pH 6.9) containing 10 ng/cm³ of Cu²⁺ as eluent solution. Copper complexes, e. g., Cu-EDTA complex, were eluted earlier than free Cu²⁺. Thus only complexed copper concentration, which was defined as "complexing capacity" could be determined accurately. Detection limit for complexing capacity with the present method was 0.3 μM. No apparent interferences with coexisting cations were observed. The present method was applied to the measurement of complexing capacity of lake water. Complexing capacity of freshwater in Lake Kasumigaura was determined to be 0.02 μM. The molecules with molecular weight more than 10000 was preconcentrated by an ultrafiltration technique.