Determination of total sulfite in liquid and solid foodstuffs is a critical, yet challenging application. A free Metrohm white paper presents 2 improved methods for simplified sulfite analysis using ion chromatographic separation followed by amperometric (method 1) and conductivity detection (method 2). While method 2 is ideally suited for higher sulfite concentrations in foods with low organic load, method 1 excels due to detection limits as low as 0.2 mg/kg as well as outstanding signal stability and repeatability of results for almost all food matrices and varying sulfite concentrations.

Current methods for sulfite analysis are either complex to apply and not reliable (Monier-Williams method) or require frequent cleaning of the working electrode (electrochemical detection applying direct current after ion chromatographic separation). The improved IC methods presented in the present white paper excel due to several reasons:

• A more alkaline stabilization solution is used in method 1 allowing the determination of total sulfite in almost all food matrices.
• A high capacity anion exchange column is used instead of an ion exclusion column for short, stable retention times and good peak shapes.
• Method 1 uses amperometric detection applying a special potential sweep (patent filed) that completely reconditions the electrodes after only 2 minutes thus overcoming the otherwise required frequent cleaning.