About Heavy Metal Limit Testing

A traditional method of heavy metal limit testing is USP 231 in which the sample is brought into aqueous solution and compounds are added that create colored precipitants in the presence of metals. This method has recently been modernized by the United States Pharmacopeia to USP 233, in which an ICP is used to determine the metal content.  This newer method will be coming more into use over the next few years. 

  • Approaches

    The traditional wet chemistry method has several limitations. It is unable to determine what metals are present, only whether or not there is more than the limit. Also in cases of non water soluble samples, mercury cannot be detected due to its volatilization during the charring step. This is the currently required method in most United States Pharmacopeia monographs. 

  • Sample Considerations

    Water samples can be tested directly.  Polymer samples are ashed in crucibles and the metals residue dissolved and tested.

    Contact us to discuss your heavy metal limit testing needs and associated sample considerations.

  • Experience

    We have experience with:

    • PLGA raw material
    • Water and water extracts
    • PEG