Detection of potassium permanganate as a food additive

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A. Determination of 5 chlorides (calculated by CI)

A.5.1 Method Summary

After treatment of the sample, chloride ions and silver ions form insoluble silver chloride in nitric acid medium.

. When the chloride ion content is low, silver chloride forms a suspension for a certain period of time, making the solution turbid. It can be used for the visual turbidimetric determination of chloride

A.5.2 Reagents and Materials; Ethanol

A.5.2.2; Nitric acid solution: 1+6

A.5.2.3; Silver nitrate solution: 100g/L

A.5.2.4 Chloride standard solution: 1mL contains 5ug of chloride (Cl), prepared before use. Transfer 5mL of chloride standard solution prepared according to GB/T602 using a pipette, place it in a 100mL volumetric flask, dilute with water to the mark, and shake well

A.5.3 Analysis Steps

A.5.3.1 Preparation of Test Solution

Weigh approximately 1.25 g of the sample to the nearest 0.001 g. Place in a 50mL beaker, dissolve in 40mL of water, add 3mL of ethanol, and heat until boiling for 2min to 3min. Cool and transfer all to a 50mL volumetric flask. Dilute the scale with water and shake well. Dry filter with medium speed quantitative filter paper and collect the filtrate (discard the first 10mL of filtrate). This solution is sample solution A (the solution should be colorless), used for the determination of chloride and sulfate content

A.5.3.2 Determination

Use a pipette to take 20mL of sample solution A, place it in a 25mL colorimetric tube, add 1mL of nitric acid solution and 1mL of silver nitrate solution, dilute with water to the mark, and shake well. Keep away from light for 5 minutes, and the turbidity should not be deeper than the standard turbidimetric solution

Preparation of standard turbidimetric solution: Use a pipette to take 10mL of chloride standard solution and handle it simultaneously with the determination of the test solution

A.6; Determination of Sulfate (Calculated as SO4)

A.6.1 Method Summary

After treatment, the sample generates insoluble barium sulfate from sulfate ions and barium ions in an acidic medium. When the sulfate ion content is low, the barium sulfate forms a suspension for a certain period of time, making the solution turbid. It can be used for visual turbidimetric determination of sulfate

A.6.2 Reagents and Materials; Acetic acid solution: 2+3

A.6.2.2; Barium chloride solution: 250g/L

A.6.2.3; Sulfate standard solution: 1mL contains 0.01mg of sulfate (SO4). Transfer 10mL of sulfate standard solution prepared according to GB/T602 using a pipette, place it in a 100mL volumetric flask, dilute with water to the mark, and shake well

Preparation of standard turbidimetric solution: Use a pipette to take 15mL of sulfate standard solution, place it in a 25mL colorimetric tube, add water to about 20mL, add 0.5mL of acetic acid solution and 1mL of barium chloride solution, dilute with water to the mark, and shake well

A.6.3 Analysis Steps

Use a pipette to take 12mL of sample solution A, and use a pipette to take 15mL of sulfate standard solution. Place it in a 25mL colorimetric tube, add water to about 20mL, add 0.5mL of acetic acid solution and 1mL of barium chloride solution, dilute with water to the mark, and shake well. Leave it for 5 minutes and the turbidity should not be deeper than the standard turbidimetric solution

A.7 Determination of Water Insoluble Matter

A.7.1 Method Summary

Weigh a certain amount of sample to dissolve in water, filter it, and dry it to constant weight under certain temperature conditions. After weighing, determine the content of water insoluble matter

A.7.2 Instruments and Equipment

A.7.2.1 Glass Sand Crucible: Filter plate aperture is 5pm~15um.

A.7.2.2 Electric oven: The temperature can be controlled between 105 ℃ and 110 ℃

A.7.3 Analysis Steps

Weigh approximately 2.5g of the sample to the nearest 0.01g, place it in a 250mL beaker, and dissolve it in 150mL of water at warm temperature.

. Filter with a glass sand crucible that has been pre heated to constant weight at 105 ℃~110 ℃, wash with water until the filtrate is completely colorless, place in an electric oven, and dry to constant weight at 105 ℃~110 ℃

A.7.4 Result Calculation

The mass fraction w2 of insoluble matter in water is calculated according to equation (A.2):

Where:

m - the mass of insoluble matter after drying, in grams (g)

m - The mass of the sample, in grams (g)

Take the arithmetic mean of the parallel measurement results as the measurement result, and the absolute difference of the parallel measurement shall not exceed 0.02%

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