Colorimetric analysis for free sulfite determination
- Kit volume: 250 ml
- Method: Two-reagent differential at 670 nm
- Limit of linearity: 150 mg/l
- Limit of detection: 3 mg/l (ppm)
- Shelf life: 36 months
Advantages
- Stable liquid reagent until the expiration date
- Ready-to-use dedicated reagent
- Liquid calibrator included in the kit
Most sulfur dioxide added to the must or wine combines with different organic compounds. This is the predominant fraction in wine; however, there is another fraction that is not combined, namely, free SO2. Although it is present in lower amounts, its antiseptic and antioxidant properties are superior to those of combined sulfite.
Free sulfite in the sample reacts with 4,4’-(4-iminocyclo- hexa-2,5-dienylidenemethylene) dianiline chromogen (pararosaniline; PR) and formaldehyde (F) in acid medium. In a second reaction, free sulfite is removed by oxidation and the rest of substances (I) that are able to react with the chromogen are measured. The difference between the results obtained from the two reactions is the free sulfite concentration.
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