IC Determination of Nitrate and Oxalate in Vegetables with Simultaneous Extraction of the Analytes

In the extraction of nitrate and oxalate from samples of vegetables (i.e.,leaf mustard and shallot),pure water containg 2 mL of 0.5 mol ·L-1 HCl was found to be the most effective among the 3 extractants tested. In the ion chromatographic determination,the IonPac AS11 column was used as stationary phase,and 8 mmol·L-1 NaOH solution was used as mobile phase to elute the anions (NO-3 and C2O2-4) from the column in succession. Range of linearity was found within 20 mg·L-1 for both the anions,using 25 μL as the amount of sample introduced. Detection limits (3S/N) of the method found were 0.02 mg·L-1 (for NO-3) and 0.05 mg·L-1 (for oxalate). Precision was tested with mixed standard solutions of NO-3 and C2O2-4 at different concentrations by 10 replicate sample introductions,giving values of RSD′s of 1.8% for NO-3 and 2.3% for C2O2-4. Recovery of the method was tested,and the values of recovery found were ranged over 95.1%-103.2% for NO-3,and 95.5%-103.6% for C2O2-4.