Import and export food/heavy metal parameter detection

The detection principle and standards for various heavy metals

1. The detection principle and standards for heavy metal arsenic

The national standard borohydride reduction colorimetric method is used, that is, the sample is digested, potassium iodide thiourea is added, and heated to reduce pentavalent arsenic to trivalent arsenic. Under acidic conditions, potassium borohydride reduces trivalent arsenic to negative trivalent, forming hydrogen arsenide that is introduced into the absorption solution and turns yellow. The arsenic content is determined by instrument detection

2. Detection principle and standards for heavy metal lead

The national standard dithizone colorimetric method is used, which means that after digestion of the sample, under weak alkaline conditions, lead ions and dithizone form a red complex, which is dissolved in trichloromethane and then colorimetric determination is carried out

3. Detection Principles and Standards for Heavy Metal Chromium

After digestion of the sample, in the presence of divalent manganese, chromium ions react with diphenylcarbazide to form a purple red complex. The color depth of the complex is proportional to the content of hexavalent chromium, and the chromium content can be determined by colorimetric measurement.

4. Detection Principle and Standards for Heavy Metal Cadmium

The national standard colorimetric method is used, which means that after digestion of the sample, cadmium ions and 6-bromophenyl thiazolylazo naphthol form a red complex under alkaline conditions, which is dissolved in trichloromethane and colorimetric determination is carried out

5. The detection principle and standards of heavy metal mercury

The national standard dithizone colorimetric method is used, which means that after the sample is digested, under acidic conditions, mercury ions and dithizone form an orange red complex, which is dissolved in trichloromethane and colorimetric determination is carried out

6. Detection Principle and Standards of Heavy Metal Nickel

The national standard dimethylglyoxime colorimetric method is used, which means that after digestion of the sample, a peroxide is added under strong alkaline conditions, and nickel and dimethylglyoxime form a reddish brown complex. The color depth of the complex is proportional to the nickel content. The nickel content can be determined by colorimetric measurement

7. Detection Principles and Standards for Heavy Metal Iron

After digestion of the sample, iron is reduced to divalent iron using a reducing agent. Within the range of pH 2-9, divalent iron reacts with o-phenanthroline to form an orange red complex. The color depth of the complex is proportional to the iron content, and the iron content can be determined by colorimetric measurement

8. Detection Principles and Standards for Heavy Metal Aluminum

The national standard chrome azure S colorimetric method is used. After digestion and treatment of the sample, trivalent aluminum ions react with chrome azure S and hexadecyl ammonium bromide in a buffer solution medium to form a blue ternary complex. The color depth of the complex is directly proportional to the aluminum content, and the aluminum content can be determined by colorimetric measurement

9. Detection Principles and Standards for Heavy Metal Zinc

The national standard dithizone colorimetric method is used. After digestion of the sample, under appropriate pH conditions, zinc ions form a purple red complex with dithizone. The color depth of the complex is proportional to the zinc content, and the zinc content can be determined by colorimetric measurement

10. Detection Principles and Standards for Heavy Metal Manganese

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