A lipid-soluble antioxidant from polyallomer centrifuge tubes.

Santowhite, a commercial antioxidant used in the manufacture of polypropylene, contaminates 12-ml polyallomer tubes to the extent of 0.2-0.3 mg/tube. It is distributed through the plastic and appears as a microscopic dust on the tubes' surfaces. In the preparation of polysomes from rat liver by standard methods, approximately 15% of the antioxidant in previously water-washed tubes was removed by suspension of the polysome pellet with stirring in 1-2 ml of Tris buffer, pH 7.8. The polyallomer impurity has been shown to be identical with Santowhite, which is 4,4'-butylidene-bis(6-tert-butyl-m-cresol), by UV, mass, and NMR spectra. It is not uniformly removed from polyallomer tubes by common detergents but is removed by washing with acetone, to which the plastic is resistant.