An alternative method for determination of additives in polypropylene using supercritical fluid extraction and enhanced solvent extraction

The extraction of Irganox 1076, Irgafos 168, and Irganox 1010 from polypropylene (PP) by supercritical fluid extraction (SFE) and enhanced fluid extraction (ESE) was investigated to find an alternative method to the dissolution extraction required by regulators for polymers used for the packaging of liquid pharmaceutical formulations. The maximum recovery with SFE was obtained at a CO2 pressure of 680 bar at a temperature of 100 degrees C, with 10% methanol as modifier and static and dynamic extraction times of 30 and 40 minutes, respectively. This gave a recovery of >= 95% for Irganox 1076 and Irgafos 168 compared to the pharmacopoeial method, and a recovery of 62% for Irganox 1010. With ESE, the maximum extraction was obtained at a temperature of 100 degrees C, a restrictor flow rate of 5mL/min, a static extraction time of 90 minutes, and a solvent mixture of 2-propanol-cyclohexane (75: 25 v/v). The recoveries for Irganox 1076 and Irgafos 168 were 109% and 121%, respectively, compared to the pharmacopoeial method, while the recovery for Irganox 1010 was 86%. When a higher temperature was used with ESE, the recoveries of Irganox 1076 and Irgafos 168 were unchanged but that of Irganox 1010 increased to 96%. Unfortunately, at the higher temperature, the PP partly melted and caused a system blockage. A better recovery than 86% of Irganox 1010 is required for a method to be an alternative to the dissolution extraction method.