Sulfurous acid is a weak acid and can be separated by ion exclusion chromatography using RSpak KC-811. (A) is a chromatogram of standards. (B) is a chromatogram of directly injection of diluted wine and only free sulfurous acid is detected. (C) is a chromatogram of diluted wine to which NaOH is added before injection. By the addition of NaOH, all sulfurous acid in the wine is converted to free sulfurous acid and the amount of total sulfurous acid can be analyzed.