Rapid and Precise Coulometric Determination of Calcium Based on Electrolysis for Ion Transfer at the Aqueous|Organic Solution Interface

A flow system was developed for the precise determination of Ca2+ based on the electrolytic ion transfer at the aqueous|1,2-dichloroethane, W|DCE, interface. N,N,N′,N′-tetraoctyl-1,3-oxapentanediamide was added to DCE to facilitate the transfer of Ca2+. The determination of Ca2+ could be achieved with an efficiency of 99.9±0.1% based on the coulomb number for the transfer of Ca2+. The coexistence of Mg2+, Na+, or K+ of concentration identical with that of Ca2+ did not give any interference. The interference from a large excess of Na+ was removed at another cell with DCE containing bis[(12-crown-4)methyl]-2-dodecyl-2-methylmalonate placed before the cell for the determination.