At present, the detection methods of sodium metabisulfite mainly include prosaniline hydrochloride spectropho-tometric method, distillation method, ion chromatography and iodometry. The prosaniline hydrochloride spectropho-tometric method requires the use of a large number of toxic reagents; The distillation method has a complex detection process and requires a long time; Ion chromatography has high technical requirements for detection equipment and detection personnel, and the detection cycle is long and the detection cost is high.

In addition, there is an on-site rapid detection kit for sulfur dioxide (iodometry). This quick test box is based on the industry standard GB/T5009.34-2003( (Determination of Sulfite in Food) is developed based on the principle that sulfites and sulfur dioxide in food can quickly react with this reagent to produce purple products. The darker the color, the higher the content of sulfur or sulfite. Visual colorimetric analysis method is used to obtain semi quantitative results of sulfite in the sample compared with standard color scale. It is easy to use, portable, real-time on-site detection, and fast detection speed (10-1 doses have the advantages of low dosage and no pollution, and have broad application prospects. The detection steps are as follows:

Detection Method of Sodium Metabisulfite

1. Weigh 1 g of the sample with a balance and cut it into small pieces as much as possible, and place it in a sample cup; Add 10 ml of distilled or purified water to a plastic graduated pipette and let it stand for more than 10 minutes. Stir or shake with a pipette to accelerate extraction. The supernatant is the sample solution.

2. Add 2 drops of test solution A and 1 drop of test solution B to the hole of the porous colorimetric tube, and mix well; Then use a 3 mI pipette to add 0.5 mI of sample solution, stir or shake well. Leave for 2 minutes to observe color changes and compare with the color chart. Result judgment: The depth of the color. If the color of the sample solution shows obvious purple or magenta, the content of sulfur dioxide in the sample can be determined by comparing the indicated values on the color card.