Removal of hydrochloric acid from sample solution for determination of alkaline metal ions and ammonium ion by ion chromatography.

A hydrochloric acid solution cannot be easily analysed for alkaline metal ions and ammonium ion by direct injection into an ion chromatograph, because the cation peaks are distorted. This situation may be encountered when crude drug samples extracted with hydrochloric acid are analysed. We presented a facile pretreatment method to remove chloride ion from the sample using silver carbonate. After removal of the AgCl precipitate by centrifugation, the resulting supernatant was applied to the analytical column. Determination of the alkaline metal and ammonium ions was performed with a nonsupressor type ion chromatograph; column, Shim-pack IC-Cl (5 mmi.d. × 150 mm): mobile phase, 5 mM nitric acid: flow rate, 1.0 ml/min: column temp, 40°C : detector, conductivity (4μS/cm FS). When the 1 M hydrochloric acid solution containing 10μg/ml of cations was treated with silver carbonate, relative standard deviations of the peak areas of Na+, K+and NH4+were 2.0, 2.2 and 1.9%, respectively. The present method was employed for the determination of the cations in the hydrochloric acid extract of licorice.