1 Scope of application

2 Methods and Principles

3 Testing Materials

• Special reagent kit: containing A test solution (barium ion control solution, used to establish reference standards), B test solution (reaction promoter), C test solution (sulfate donor, core reaction reagent);

• Auxiliary tools: Precision balance (sensitivity 0.1g), 10mL colorimetric tube (2 tubes/group, with scale), dropper (used with matching reagents), stirring rod.

4 Operation steps

1. Sample processingWeigh 1g of the sample to be tested with a balance, place it in a clean container, add purified water to the 10mL mark, stir thoroughly to dissolve the sample completely; Let it stand for 5 minutes, and after the impurities precipitate, take 5mL of the supernatant and add it to the first 10mL colorimetric tube (referred to as the "sample tube").

2. Comparison control preparationTake the second 10mL colorimetric tube (referred to as the "control tube"), add 5mL of purified water directly, and then add 2 drops (about 0.1mL) of test solution A. Gently shake well to establish a barium ion standard reference system.

3. Reaction operationAdd 4 drops of B test solution to the sample tube and control tube respectively, cover the tube tightly, invert and shake well; Then add 4 drops of C test solution to each of the two tubes, shake well again, and let it stand for 3 minutes.

5 Results Determination

• Salt samplesIf the white turbidity depth of the sample tube exceeds that of the control tube, it is determined that the barium ion exceeds the standard and does not meet food safety requirements.

• Other food samplesWhen the white turbidity of the sample tube is deeper than that of the control tube, it indicates that the concentration of barium ions in the sample is greater than 15mg/kg and further processing is required.

• Poisoning/poisoning residueIf the sample contains a high dose of barium ions, a very obvious white turbidity will appear after the reaction, which can be quickly preliminarily determined as a sample related to barium salt poisoning.

6 Precautions

• The reagent kit should be stored in a cool and dry place away from light and sealed. Before use, check the shelf life. If the reagent changes color or becomes cloudy, it cannot be used.

• The sample dissolution should be sufficient, especially for solid samples other than table salt, to avoid incomplete dissolution that may result in incomplete release of barium ions and affect the detection results.

• When adding reagents, the dropper should be kept vertical to ensure uniform volume of each drop and reduce operational errors; The order and interval of adding two tubes of reagents should be consistent.

• When judging the results, the two tubes should be placed under a white background and observed horizontally to avoid direct light affecting the degree of turbidity judgment; Positive samples should be properly retained and sent to the laboratory for precise quantification using national standard methods.