Abstract: A method for precise quantitation of sulfate in standard solutions by ion chromatography with suppression conductivity detection has been developed. The separation of sulfate was conducted on an IonPac AS19 anion exchange column (2 mm×250 mm) with NaOH solution as isocratic eluent. The injection volume was 25 μL. An orthogonally designed experiment was carried out to evaluate the effects of the experiment factors, such as column temperature, concentration of eluent NaOH, flow-rate of the eluent, and cell temperature. The optimal chromatographic conditions obtained were as follows: column temperature, 30 ℃; NaOH concentration,  30 mmol/L; flow-rate of the eluent, 0.25 mL/min; cell temperature, 35 ℃.The detection limit (3σ) was 0.005 mg/L. On the level of 4.5 mg/L sulfate, the relative standard deviation (RSD) was 0.44% (n=8). The linear range of calibration curve was 1.0-50.0 mg/L. The reliability of method was shown by the evaluation of stability of calibration curves. The variance analysis showed that the intercept and slope of 7 calibration curves were controlled statistically in the desired range. The reliability of method was shown by quality control samples, where RSD and relative error were less than 0.9%, and 0.8%, respectively. Average recovery of standard addition was 95.5%-105%. The method has been applied to the  quantitation of sulfate in standard solution.

Key words: standard substance , sulfate, ion chromatography (IC)