USP Tests for Plastic Containers

USP <661> includes tests for leaching plastics with Purified Water (120 cm² in 20 mL at 70^oC for 24 hr) and the analysis for contaminants such as non volatile residue, residue on ignition, buffering capacity, and heavy metals. None of these tests identify specific contaminants. In addition to these non specific tests, we can offer several others which are more comprehensive and identify specific contaminants. We would recommend using the same area/volume ratio and leach time specified in USP <661>, however these additional tests will require different leachate solutions and temperatures. You may wish to test for any or all of the following:

1. pH of the purified water leachate.

2. Volatile Organic Compounds (VOCs) including such compounds as monomers (acrolein, styrene, vinyl chloride, vinyl acetate, acrylic esters) and solvents (acetone, chloroform, 1,4-dioxane, acetonitrile, etc.). This test is based on purge and trap sample concentration coupled with GCMS. The test includes quantitation of more than 25 VOCs (pdf file) and estimates any other compounds identified in the chromatogram. . The preferred leachate liquid is water or methanol. The detection limit is approximately 1-5 ug/L in water

3. Semivolatile Organic Compounds (SVOCs) including plasticizers (phthalates and adipates), phenols, polynuclear aromatic compounds, antioxidants (BHT and BHA), and other organic compounds. Fatty acids used as mold release agents may also be detected.  The test is based upon extraction into methylene chloride followed by GCMS. It includes the quantitation of over 60 target analytes (pdf file)  and estimates of other compounds found in the chromatogram. The preferred leachate liquid is water, saline, or methylene chloride.

4. Antioxidants by HPLC to determine high molecular weight compounds which are not amenable to GCMS. The test is based upon extraction followed by reverse phase HPLC with UV detection. It quantitates approximately 6 antioxidants such as BHT, Irganox products, and Tinuvin. The preferred leachate liquid is water, saline, or acetonitrile.

5. Anions by Ion Chromatography to determine several inorganic and organic anions as follows (separate IC analysis conditions required for each group): (a) fluoride, chloride, bromide, nitrate, nitrite, phosphate, and sulfate; (b) acetate, formate, and butyrate: (c) citrate; (d) ascorbate and oxalate.  The preferred leachate liquid is water or dilute sodium hydroxide. The detection limit is approximately 0.1 ug/mL.

6. Formaldehyde by HPLC which may include other aldehydes and ketones such as acetone*, acetaldehyde, acrolein*, benzaldehyde*, benzophenone*, cyclohexanone*, furfural*, glutaraldehyde, methyl ethyl ketone*, and methyl isobutyl ketone*. Some of these compounds are used in flavors (benzaldehyde) or preservatives (glutaraldehyde), and others are common solvents (MEK, MIBK, cyclohexanone). The test is based upon derivatization with dinitrophenylhydrazine (DNPH) followed by reverse phase HPLC with UV detection at 360 nm. The compounds flagged (*) can also be determined in the VOC and SVOC tests described above. The preferred leachate liquid is water or saline. The detection limit is approximately 10 ug/L.

7. Silicone as polydimethylsiloxane determined by hydrolysis, derivatization, and GC-FID. Silicones are common in containers and medical devices. While such silicones are generally very insoluble in water, lipophilic components may leach low molecular weight fractions of the silicone.  Also, some water soluble silicones such as Simethicone, are used as surfactants and anti-gas additives. The preferred leachate liquid is water or saline. The detection limit is 5 ug/mL.

8. Alcohols such as methanol, ethanol, isopropanol, and butanol determined by direct aqueous injection GC-FID. These compounds are analyzed separately from the VOCs because their water solubility and/or low molecular weight complicate analysis by purge and trap GCMS. The detection limit is approximately 1 ug/mL in water. The preferred leachate liquid is water.

9. Metals determined by ICPMS. This test includes over 60 elements. Some metals such as zinc salts of fatty acids are used as mold release agents; other metals are used as stabilizers in plastics such as vinyls. . The preferred leachate liquid is dilute nitric acid.   The detection limit is 0.1-10 ug/L in the leachate

10. EDTA by HPLC. The preferred leachate liquid is water or saline. The detection limit is 20 ug/mL.

Other tests are also available. In choosing a leachate liquid for these tests, note that organic compounds will leach to a much greater extent into organic solvents. Therefore, leaching with an organic solvent will approximate the total amount of a leachable compound in the sample, while an aqueous leachate may approximate the dose from exposure. The use of a drug product or buffer without active ingredients is generally not possible due to the presence of materials which would interfere with trace level analysis.  For a quotation...