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+1 (801) 290-7500
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Physicochemical USP Plastics Tests

The USP Physicochemical test series is designed to aid in characterizing both the physical and chemical properties of plastics or polymers. This method is intended for homogeneous plastic samples, though it may be applied to other sample types if requested.

Testing is necessary in order to comply with USP General Chapter 32 and National Formulary 27, 2009 regulations. The procedure is described in the USP General Chapter 661. Nelson Labs offers extensive experience testing different types of plastics.

Applicable Standards

  • USP 661

Testing Locations

  • Salt Lake City, UT, USA
  • Leuven, Belgium

Study Outline

USP Physicochemical testing may consist of four analyses: buffering capacity, nonvolatile residue (NVR), residue on ignition (ROI), or heavy metals.

Sample Extraction
The sample is extracted in the required extraction media at 70 ± 2°C (water and alcohol) or 50 ± 2°C (hexanes) for 24 ± 2 hours. Other extraction times and temperatures may be used if requested, but the USP General Chapter 661 limits may not be applicable.

For polyethylene or polypropylene samples, the recommended tests are heavy metals (water extraction only) and NVR (water, alcohol, and hexanes extractions). The buffering capacity test (water extraction only) is also recommended when the samples may be in contact with oral liquids.

For general plastics, all four analyses are recommended using a water extraction. The ROI test is not required when the nonvolatile residue does not exceed 5 mg.

Buffering capacity: This test measures the amount of acid or base that is added to the extract which causes a significant change in ion activity (pH).

Nonvolatile residue (NVR): This test quantifies any substances in the extract which do not volatilize at or above a temperature of 105°C.

Residue on ignition (ROI): This test quantifies any substances from the nonvolatile residue test which do not volatilize at or above 600°C in the presence of sulfuric acid. An NVR test must be performed prior to an ROI test.

Heavy metals: This test detects metallic impurities found in the extract that are colored by the sulfide ion. The metals which normally respond to this test are lead, mercury, bismuth, arsenic, antimony, tin, cadmium, silver, copper, and molybdenum. The total amount of heavy metals cannot exceed 1 part per million (ppm).

If you have additional questions about Physicochemical USP Plastics tests, or would like to consult with the experts at Nelson Labs, just send us a request or call us at (801) 290-7500.