Flow injection analysis with tubular membrane ion-selective electrodes in the presence of anionic surfactants

Abstract

Calcium ion-selective electrodes based on calcium bis{di[4-(1,1,3,3-tetramethylbutyl)phenyl]phosphate} with trioctyl phosphate in poly(vinyl chloride) have improved resistance to interference by anionic surfactants when used in flow injection analysis. Tubular membrane electrodes have been used in flow injection analysis for determining calcium ion levels in selected potable and raw water and the data agree well with determinations by atomic-absorption spectroscopy and EDTA titration.

Tubular membrane electrodes with improved membrane sensor have the potential for the determination of free calcium ions for a concentration as low as 10^–4M in the presence of a moderate background concentration of detergent, but this is poor compared with the concentration of ⩽10^–5M, which can be attained by the conventional type electrode with the same membrane system under static conditions.