Sulfite (free) Test Kits
Visual Kits
| Range | MDL | Method | Kit Catalog No. | Refill Catalog No. |
|---|---|---|---|---|
| 2-20 ppm as SO3 | 2.0 ppm | Iodometric | K-9602 | |
| 5-50 ppm as SO3 | 5.0 ppm | Iodometric | K-9605 | |
| 10-100 ppm as SO3 | 10 ppm | Iodometric | K-9610 | |
| 50-500 ppm as SO3 | 50 ppm | Iodometric | K-9650 | |
| 10-100 ppm as SO2 | 10 ppm | Ripper (Sulfite in Wine) | K-9610W |
Methods
Sulfite is not usually present in surface waters. If sulfite is discharged in effluents or from domestic wastewaters, it readily oxidizes to form sulfate. Sodium sulfite is the most common form of sulfite and is an excellent reducing agent with applications as an oxygen scavenger. Sulfite concentrations in boiler and process waters must be monitored routinely to avoid overtreatment. Waste treatment plants that use sulfur dioxide to remove excess chlorine must monitor their effluents for sulfite.
Sulfites have been used for centuries to sanitize and preserve foods. They are used worldwide in the wine industry as antioxidant and antimicrobial agents. However, sulfites have been identified as causative agents in certain allergic reactions suffered by asthmatics. As a result, the FDA and the Bureau of Alcohol, Tobacco, and Firearms have mandated that sulfites in foods and beverages, at levels of 10 ppm or higher, be identified on the label.
References: ASTM D 1339-84, Sulfite Ion in Water, Test Method C. APHA Standard Methods, 22nd ed., Method 4500-SO32– B – 2000. USEPA Methods for Chemical Analysis of Water and Wastes, Method 377.1 (1983).
CHEMetrics’ sulfite test kits employ the iodometric chemistry in which sulfite is titrated with iodide-iodate titrant in an acid solution using a starch indicator. Thiosulfate will titrate as sulfite. Sulfamic acid is added to the sample to prevent interference from nitrite. Results are expressed as ppm (mg/L) SO3.
References: ASTM D 1339-84, Sulfite Ion in Water, Test Method C. APHA Standard Methods, 22nd ed., Method 4500-SO32– B -2000. USEPA Methods for Chemical Analysis of Water and Wastes, Method 377.1 (1983).
CHEMetrics’ sulfite test kit is based on the Ripper method, which the wine industry has used for years as a standard for rapid sulfite analysis. Sulfite is titrated with an iodide-iodate solution, using a starch end point indicator. Phosphoric acid is used to adjust the pH of the sample.
Results are quantified using direct-reading titration cells. The test determines free sulfite as ppm (mg/L) SO2.Results for this test kit are acceptable for white wines (although they can have an error of up to 10 ppm). This test kit is not recommended for use with red wines or white wines containing ascorbic acid or tannin. These wines often give false high test results.