[The problem and improvement of colorimetric method for determination of sulfite in foods containing sulfur compounds].

The modified Rankine colorimetric method for measuring sulfite added to food as a food additive has a low determination limit and is little influenced by interfering substances from foods. However, it can give erroneous results for foods containing Liliaceae Allium. So, four different methods, alkaline titration, a colorimetric method, ion chromatography and qualitative analysis with potassium iodate-starch paper, were examined. It was found that the sodium azide used in the colorimetric method forms sulfur dioxide during bubbling and heating. The proposed colorimetric method can be applied to food containing sulfur compounds, if sodium azide is omitted and 1% triethanolamine solution is used as an absorbent instead of 0.1 mol/L sodium hydroxide solution.