Determination of Chloride Ion in Panax Notoginseng by Ion Chromatography with Water Bath Extraction and n-Hexane Purification

The fresh Panax notoginseng sample was washed with water, blanched at 80 ℃, dried, crushed and sieved. An aliquot (2.000 0 g) was taken and mixed with 40 mL of water, and the mixture was extracted in 90 ℃ water bath for 60 min. After cooling to room temperature, the mixtue was diluted to 50 mL with water, and centrifuged for 3 min. An aliquot (8 mL) of supernatant was taken, and 2 mL of n-hexane was added. The mixed solution was swirled for 1 min, and centrifuged for 3 min. The lower aqueous phase was taken, and passed through a 0.22 μm aqueous filter membrane. The filtrate was used for ion chromatography analysis. IonPac AS15 chromatographic column was used as the stationary phase, and 30 mmol·L^-1 potassium hydroxide solution was used as the eluent. The chloride ion was obtained by isocratic elution at a flow rate of 1.0 mL·min^-1, and analyzed by the conductivity inhibition detector. As found by the results, values of mass concentration and peak area of chloride ion were linearly related in the range of 0.05-20.00 mg·L^-1, with detection limit (3s) of 0.005 mg·L^-1. The spiked recovery test was carried out on the actual sample at three concentration levels, giving results of recovery of chloride ion in the range of 85.4%-105%, and RSDs (n=6) of the determined values ranged from 2.8% to 4.2%. The proposed method was applied to the analysis of actual sample, and compared with high temperature dry ashing method given from reference. The determined values were basically consistent, and the proposed method had better precision.