Analysis of poly(vinyl chloride) additives by supercritical fluid extraction and supercritical fluid chromatography

Abstract

The use of supercritical fluid extraction (SFE) as an alternative to liquid extraction was investigated. Supercritical CO₂ was used to extract additives in poly(vinyl chloride)(PVC). The extraction time, temperature and pressure were varied in order to determine the optimum SFE conditions. The effects of the particle size of the sample and the addition of methanol to the extraction fluid were also investigated. The separation and quantification of individual components in the PVC extracts were carried out off-line using packed column supercritical fluid chromatography (PSFC). This technique combined good resolution, rapid analysis times and linear calibrations over a wide range of additive concentrations. By using SFE, 29.2% m/m of the sample was extracted of which 66.7% m/m was diisooctyl phthalate (DIOP). This compared with the existing liquid extraction method by which 30% m/m of the sample was extracted of which 67% was DIOP. The total extractions varied by 0.9% relative standard deviation (RSD) and the DIOP content varied by 1.2% RSD.