950 (2002) 31–39 Journal of Chromatography A, www.elsevier.com / locate / chroma Analysis of citrates and benzoates used in poly(vinyl chloride) by q supercritical fluid extraction and gas chromatography a b b c, * ´ ´ ´ R.M. Guerra , M.L. Marın , A. Sanchez , A. Jimenez a Centre of Biomaterials, University of Havana, BOX 6130, 10600 Havana, Cuba b Institute of Toys Technology (AIJU), Av. Industria s / n, 03440 Ibi (Alicante), Spain c Analytical Chemistry Department, University of Alicante, P .O. Box 99, 03080 Alicante, Spain Received 12 June 2001; received in revised form 9 January 2002; accepted 9 January 2002 Abstract Supercritical fluid extraction (SFE) has been demonstrated to be a useful tool in the determination of additives in polymeric materials. This paper describes the determination of some citrates and benzoates in poly(vinyl chloride) blended with 33–34% of plasticizer using off-line SFE followed by gas chromatography. Experimental factors affecting SFE have been studied by gravimetric analysis, followed by analysis of the extracts using a gas chromatograph equipped with a flame ionization detector. The extraction process is governed by the solubility of the plasticizers in the supercritical fluid or by their diffusion through the polymer matrix, which depend on the pressure and temperature used. Maximum extraction (.99%) is obtained at pressures and temperatures higher than 40 MPa and 80 8C, respectively. Due to purge losses, the collection efficiency of plasticizers into a liquid solvent ranges from 85 to 90%. The applicability of the SFE method is demonstrated using real samples and comparing the results with those obtained by conventional Soxhlet extraction.  2002 Elsevier Science B.V. All rights reserved. Keywords: Supercritical fluid extraction; Citrates; Benzoates; Poly(vinyl chloride); Polymers 1. Introduction ing Soxhlet, are normally used. Although this tech- nique has been shown to be effective for the The analytical determination of low-molecular- extraction of analytes from many different samples, mass molecules used as additives in polymers is a the method is time-consuming and often requires the increasingly studied subject. Conventional extraction use of large amounts of toxic solvents, which is techniques such as liquid solvent extraction, includ- environmentally unsound [1]. For this reason, in the last decade, novel analytical methods, such as super- critical fluid extraction (SFE) and microwave-as- q Presented at the 30th Scientific Meeting of the Spanish Group sisted extraction (MAE), have been developed. of Chromatography and Related Techniques / 1st Meeting of the SFE has been used extensively as a quantitative Spanish Society of Chromatography and Related Techniques, procedure for a variety of analytes including poly- Valencia, 18–20 April 2001. meric materials [2]. For instance, on-line SFE cou- *Corresponding author. ´ E-mail address: alfjimenez@ua.es (A. Jimenez). pled to capillary supercritical fluid chromatography 0021-9673 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0021-9673(02)00051-1