A microgap impedance sensor for the determination of trace water in organic solvents

Abstract

A microgap impedance sensor with a 50 μm gap was developed for the determination of trace water in organic solvents by coating poly(dimethyldiallylammonium chloride) (PDMDAAC) and ferricyanide/ferrocyanide composite materials on indium tin oxide (ITO). The electrochemical properties of the composite materials were investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We observed that the impedance response of the sensor depended on the concentration of trace water in the organic solvents. Under optimized conditions, the linear range for the determination of trace water was 0–0.06% for chloroform (CHCl₃), 0–0.10% for acetone (CH₃COCH₃), 0–0.12% for tetrahydrofuran (THF), and 0–0.10% for acetonitrile (CH₃CN), and the detection limits were 0.65, 1.54, 0.61, and 1.72 ppm, respectively. The results obtained from the impedance sensors were comparable to those obtained using the traditional Karl Fischer method.