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Physicochemical Testing Checks on Safety of Extracts

By Dallas Dean, Study Director, Chemistry

Physicochemical testing following the USP 661 standard is conducted to ensure potential extracts of plastic drug containers are safe. With all of the different polymers used to manufacturer containers, the physicochemical tests look for potential extractables from the containers.

Four different tests are generally included.

  • The Non-Volatile Residue (NVR) test is performed gravimetrically using a 50mL aliquot of extract from a sample. The extract is evaporated below the boiling point of the solvent and then subjected to 105ºC. The remaining residue is weighed and the result is applied to the pass/fail criteria found in USP 661. The test is not an identification test – it shows how much non-volatile material is present in the extract.
  • Residue On Ignition (ROI) –If the non-volatile residue is above the 5mg the ROI test is performed.  The residue is subjected to an acid digestion and then 600ºC. Residues that remain after this process are generally salts or metals. This test is also a quantitative test.
  • Buffering Capacity – This test is a measurement of the sample extracts’ resistance to a change in pH.
  • Heavy Metals Test – Using a positive control and a lead standard at a known concentration, the colorimetric heavy metal test the extract is reacted under the same conditions as the control. The sample extract is visually compared to the control and the pass/fail criteria are applied.

These physiochemical tests will help manufacturers know if their device fulfills USP 661 limits. Nelson Laboratories can help determine the right test to perform based upon their needs.