Design of double cell quartz crystal detector for ion chromatography and its applications to determination of organic acids in traditional Chinese herb medicine

A double cell quartz crystal (DCQC) detector in combination with a single-column IC chromatographic flow system has been developed. First, an electrical equivalent circuit model was built, which was used to determine the optimum detector parameters including the cell constants and the background conductance of the adjusting cell. This method has a low temperature coefficient and a high conductance sensitivity independent of the background from 7.2 to 2500 mu S. The detection limit is 0.05 ppm and the linear dynamic range is up to 72 ppm. This detector was applied to determination of citric acid, malic acid and ascorbic acid in Chinese herb medicines including fructus mume and ephedra sinica stapf.