Elemental and Trace Metal Analysis can be carried out in accordance to Pharmacopoeia USP 232 or Ph. Eur. 2.4.8 or USP <231> or to specific customer requirements.
The term "heavy metal" is not scientifically well-defined. Different elements may be classified here depending on the classification criteria (density, number of periods, etc.). Technically, any metal with a density greater than 5 g/cm3 is considered a heavy metal. "Heavy metals" usually means toxic elements, however, this is only partially true, as the small amounts of elements essential to human life also fall into this category.
If testing is not performed for a specific heavy metal, the most common source of evidence nowadays come from a limit test being carried out. After treatment, the heavy metal is complexed with thioacetamide or precipitated as a sulphide. Then, one compares the resulting colouring of the sample solution against that from a reference lead solution.
These limit tests still form the majority of testing for heavy metals in the current national and international Pharmacopoeias (e.g. Ph. Eur. 2.4.8 or USP <231>). Thereby, it is possible however to make only a semi-quantitative statement about the total contents of heavy metals in the sample, and in addition - and additionally, only for those heavy metals that actually form dark coloured complexes or sulphides.
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