Flow-injection analysis with a coated tubular solid-state copper(II)-selective electrode

Abstract

The incorporation, behaviour and suitability of a home-made coated tubular solid-state copper(II)-selective electrode into the conduits of a flow-injection system is described. The compact tubular sensor (volume 7.8 μl) is constructed from a copper tube and Tygon tubing, treated with ammonium sulphide to give the copper/copper sulphide electrode and conditioned in an ascorbic acid medium. Interferences of foreign ions are similar to those found in batch analysis, but are less severe in the flow-injection system. Changes in carrier stream pH between 1 and 3 affected the electrode response, but sample pH has no or little influence in the range 1–7 depending on the copper(II) ion concentration in the samples. With 30-μl samples the flow-through electrode system covers a working range up to 5000 mg dm −3 with a detection limit of 0.5 mg dm −3. The system is suitable for the determination of copper(II) in effluent and tap water (relative standard deviation < 1.75% for 0.5–912 mg dm −3 copper) and acidic copper sulphate plating solutions (relative standard deviation < 1.21% for 87–4135 mg dm −3 copper) at a sample frequency of about 80 h −1. The results obtained agree well with results by a standard atomic absorption spectrometric method.