What are the inspection methods for heavy metals? What drugs are suitable for heavy metal detection?

Thioacetamide was used as chromogenic agent in acetic acid solution with pH 3.5. It is suitable for most drugs that are soluble in water or ethanol and stable under acidic conditions.

2. Ignition residue method

Take the residue left under the ignition residue and operate according to thioacetamide method. Suitable for organic drugs that are insoluble in water or ethanol or can form coordination compounds with heavy metal ions.

3, sodium sulfide method

Under alkaline conditions, sodium sulfide is used as chromogenic agent. It is suitable for drugs insoluble in dilute acid but soluble in alkaline aqueous solution.

4, microporous membrane method

According to thioacetamide method, the generated sulfide is enriched on microporous membrane, and the color points are compared. Suitable for drugs with low limit of heavy metals.

Matters needing attention

1, heavy metal in acidic solution, using thioacetamide to produce hydrogen sulfide as chromogenic reagent, such as sodium sulfide test solution, is easy to decompose and separate out sulfur, which causes turbidity and affects colorimetry. In alkaline solution, sodium sulfide reagent is used as chromogenic agent.

2. When the standard lead sampling amount is about 20μg, it is suitable for visual inspection. If it is less than 10μg, the color development is too light. If it is as high as 30μg, the color is too deep to be observed and distinguished.

3. The existence of trace iron ions affects the detection of heavy metals, and vitamin C can be added to reduce them to ferrous ions to eliminate the interference.

4. If the drug itself affects the inspection of heavy metals, a masking agent can be added.

5, in order to eliminate the reagent may be mixed with heavy metals, such as the use of hydrochloric acid more than lml, ammonia test solution more than 2ml, and organic destruction with sulfuric acid or nitric acid, or add other reagents, unless otherwise specified, the control solution should take the same amount of reagent in the crucible or porcelain roar after evaporation, check according to law.

The above contents refer to Baidu Encyclopedia-Test Method for Heavy Metals.