Determination of Tinuvin 622 in polyethylene samples by liquid chromatography with ultraviolet absorption detection

This work describes the procedure for determining the quantity of the light stabilizer Tinuvin 622 or similar (4-hidroxy-2,2,6,6-thetramethyl-1-piperidine ethanol polymer) in polyethylene samples. The technique used was high performance liquid chromatography (HPLC) in both phases: normal and reverse. Two methodologies to obtain the reference compound (Diol 622) are presented at the beginning of the paper. These methodologies describe the Tinuvin 622 saponification with potassium hydroxide or with thetrabuthylammonium. hydroxide, both in methanol agent. After that, the quantitative analytical determination of diol using HPLC in both phases (normal and reverse). An amino column (4,6 x 250 mm I.D., 5 pm) and n-hexane/ethanol (93:7) mixture as mobile phase were employed in the normal phase. Whereas, an octadecyl silane column (3,9 x 150 mm I.D., 5 pm) and water/ethanol mixture (93:7) were used on the reverse phase. In both methods, an ultraviolet scan at 2 10 nm was the applied. Both chromatographic methods were applied to rothomolding-grade-polyethylene resins. The obtained results shown that both proposed methods could be used for to determine this additive at usual commercial concentrations in these samples (0.20%).