Separation and identification of stabilizers used in the manufacture of HDPE are necessary in order to correlate performance properties with polymer composition. This test method provides a means of determining BHT, BHEB, Isonox 129, Irganox 1010, and Irganox 1076 levels in HDPE samples. This test method should be applicable for the determination of other antioxidants such as Cyanox 425, Cyanox 1790, Cyanox 2246, Ultranox 236, and Ultranox 246, but the applicability of this test method has not been investigated for these antioxidants.

The additive-extraction procedure is made effective by the insolubility of the polymer sample in solvents generally used for liquid chromatographic analysis.

The lowest level of detection for a phenolic antioxidant is approximately 2 ppm under optimum conditions.

Other procedures that have been used successfully to remove additives from the plastics matrix include thin-film, microwave,¹⁰ ultrasonic,¹¹ and supercritical fluid extractions.^{11 , 12 , 13} Procedures other than HPLC have been used successfully to separate additives, including SFC¹³ and capillary GC.¹⁴