Total Sulfur Dioxide Determination in Red Wine by Suppressed Ion Chromatography with In-Sample Oxidation and SPE

Suppressed ion chromatography (IC) based on in-sample oxidation and SPE is described for total sulfur dioxide determination in red wines. In this method, sulfur dioxide was converted to stable sulfate ion through a simple H2O2 oxidation step and then the impurities were removed with C-18 micro-column SPE pretreatment. Finally, the sulfate was determined by suppressed ion chromatography coupled with conductivity detection and the content of total sulfur dioxide could be obtained through sulfate content by blank deduction method. By using a mixture of NaHCO3 and Na2CO3 as mobile phase, the analysis of one sample with nine anions could be completed within 25 min. For sulfate detection, a linear calibration curve with correlation coefficient of 0.9993 was obtained from the peak area with low detection limit (0.45 mg L−1, 3σ) and excellent repeatability (RSD = 1.12%, n = 6). This method was applied to sulfur dioxide determination in real wine samples and compared with conventional iodometry.