Comparison of methods for quantitative analysis of additives in low-density polyethylene using supercritical fluid and enhanced solvent extraction

On-line supercritical fluid extraction-supercritical fluid chromatography ( SFE-SFC) with cryogenic trapping was used to extract and separate five addi tives from a low-density polyethylene (LDPE) sample. A glass tube filled wi th glass wool afforded excellent collection efficiency for the extracted an alytes. Additive spiked sand was employed to optimize the various parameter s of the on-line SFE-SFC system. Calibration curves from the spiked sand st udies for on-line SFE-SFC were obtained with good linearities for quantitat ion. Results obtained on additives in LDPE from on-line SFE-SFC were compar able to those from off-line SFE-HPLC and off-line enhanced solvent extracti on (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 a nd off-line ESE-HPLC due to the small sample size employed in the on-line s ystem. Considerable clean-up of the ESE extract was required prior to chrom atographic analysis. On-line SFE-SFC minimized the sample handling and elim inated the use of organic solvent. Despite the lower than expected precisio n, the on-line SFE-SFC method for quantitation of polymer additives appears to be reliable and robust for application in routine quality control analy sis. (C) 1999 Elsevier Science B.V. All rights reserved.