Journal of Chromatography A, 858 (1999) 209–218 www.elsevier.com / locate / chroma Comparison of methods for quantitative analysis of additives in low-density polyethylene using supercritical fluid and enhanced solvent extraction * L.Y. Zhou, M. Ashraf-Khorassani, L.T. Taylor Department of Chemistry, Virginia Tech, Blacksburg, VA 24061-0212, USA Received 12 January 1999; received in revised form 6 April 1999; accepted 10 June 1999 Abstract On-line supercritical fluid extraction–supercritical fluid chromatography (SFE–SFC) with cryogenic trapping was used to extract and separate five additives from a low-density polyethylene (LDPE) sample. A glass tube filled with glass wool afforded excellent collection efficiency for the extracted analytes. Additive spiked sand was employed to optimize the various parameters of the on-line SFE–SFC system. Calibration curves from the spiked sand studies for on-line SFE–SFC were obtained with good linearities for quantitation. Results obtained on additives in LDPE from on-line SFE–SFC were comparable to those from off-line SFE–HPLC and off-line enhanced solvent extraction (ESE)–HPLC for all additives except Irganox 1076. However, the precision obtained with on-line SFE–SFC was lower than that from off-line SFE–HPLC and off-line ESE–HPLC due to the small sample size employed in the on-line system. Considerable clean-up of the ESE extract was required prior to chromatographic analysis. On-line SFE–SFC minimized the sample handling and eliminated the use of organic solvent. Despite the lower than expected precision, the on-line SFE–SFC method for quantitation of polymer additives appears to be reliable and robust for application in routine quality control analysis.  1999 Elsevier Science B.V. All rights reserved. Keywords: Supercritical fluid extraction; Enhanced solvent extraction; Low-density polyethylene; Polyethylene 1. Introduction time-consuming and uneconomical. They involve dissolution of the polymer in a hot solvent such as As the purity and amount of additives incorporated toluene [1], chloroform, or decalin [2], followed by into a polymer product affect the properties of the precipitation of the high molecular weight fraction polymer, there is a need for reliable and rapid with an alcohol or by cooling. Further separation of analytical methods to characterize the additives and the extractables is usually required prior to analysis. to determine the amount of additive present. Tradi- Analysis by conventional GC is limited [3] because tional liquid solvent–polymer extraction methods are many additives are non-volatile and high molecular weight. Aluminum-clad high-temperature capillary GC columns have been used but such methods have been found to lack reproducibility [4]. Owing to the *Corresponding author. Tel.: 11-540-231-6680; fax: 11-540-231- relatively high molecular weight, reactivity, polarity, 3255. E-mail address: ltaylor@chemserver.chem.vt.edu (L.T. Taylor) thermolability, and volatility of certain additives, LC 0021-9673 / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0021-9673(99)00729-3