Ion Chromatographic Determination of Inorganic Anions in Tea

Ion chromatography was applied to the determination of 6 inorganic anions F-,Cl-,Br-,NO-3,H2PO-4 and SO2-4 in tea.The 6 anions in the sample were extracted ultrasonically with water for 20 min,at 95 ℃.The extract was then passed through the IonPac AS11-HC anion-exchange column with AG11-HC protective column.Gradient elution was used to desorb the anions from the column by KOH solution with its concentration varied from 15 mmol·L-1 to 30 mmol·L-1.Linear relationships between values of peak area and mass concentration of F-,Cl-,SO2-4 were obtained in the range of 0.01-150 mg·L-1,and those of the H2PO4,NO-3,Br-were obtained in the range of 0.05-150 mg·L-1.Detection limits(3/N) of 6 inorganic anions were less than 0.03 mg·L-1.The proposed method was used in the determination of 6 inorganic anions in tea sample,values of recovery found by standard addition method were in the range of 90.9%-100.0%,with values of RSD′s(n=5) less than 3.5%.