Gas chromatographic determination of acid‐catalyzed transesterified antioxidant additive irganox 1076® in polypropylene

The transesterification by means of methyl alcohol of a low vapor pressure antioxidant additive, n ‐octadecyl‐β‐(3,5‐di‐ tert ‐butyl‐4‐hydroxyphenyl)propionate‐Iraganox 1076 ® (produced by Ciba‐Geigy) was studied. The classical method to prepare methyl esters from triglycerides in lipids was applied with use of sulfuric acid as a catalyst. The optimum reaction conditions were sulfuric acid concentration of 1 w/v% in methyl alcohol, temperature of 75°C, and time of 2 hours. The contents of the additive were determined by gas‐liquid chromatography (GLC) of a portion of transesterificate using 10% SE‐30 on Gaschrom Q (60–80 mesh) or 5% Silicone OV‐17 on Shimalite W (80–100 mesh) as a packing reagent. Irganox 1076 in polypropylene was extracted with n ‐hexane. Many interfering substances in the GLC could be completely removed by the Florisil column treatment of n ‐hexane extract. The relative standard deviation was 2.7% for Irganox 1076 at levels corresponding to 0.0142 wt% in polypropylene. The limit of detection was 5 μ/g in polypropylene.