A yellow compound was isolated from commercially available, discolored, polyethylene ophthalmic closures containing titanium dioxide and butylated hydroxytoluene (I). This compound was present at 7.46 ppm (w/w). It was identified by UV, IR, and mass spectra as 3,3',5,5'-tetrabis(tert-butyl)stilbenequinone (II), a dimer of I. Further structural confirmation was obtained by NMR. Formation of II is catalyzed by titanium dioxide.