After sample preparation, 25L of the sample solution were injected into the HPLC. The flow rate was set at 0.6mL/min. Detec-tion at the platinum cell was at 200mV at a range of 20nA. One run was finished within 8min. Two chromatograms of a sulfite standard solution (c = 0.4mol/LSO2) analyzed with and without enzyme reactor, respectively, are shown in Fig. 2. A chromatogram of a grape juice sample is displayed in the top right of Fig. 2.