Supercritical fluid extraction for the analysis of liquid poly(alkylene glycol) lubricants and sorbitan ester formulations

Abstract

Additives were selectively extracted from poly(alkylene glycol)(PAG) lubricant formulations using supercritical fluid extraction. The PAG matrix was adsorbed onto silica for the extractions and the extracted analytes were passed through a silica column positioned in-line in the supercritical fluid stream. The selectivity obtained by this method was compared with that obtained by the direct extraction of adsorbed and unadsorbed PAG and by the extraction of unadsorbed PAG through the in-line column. The final procedure was found to be successful in separating additives from all but the lowest molecular mass PAG oligomers. Further use of this procedure was demonstrated by a stepwise extraction of a sorbitan ester formulation. This gave a chemical-class fractionation of the product and so provided a sample preparation technique for further spectroscopic analysis.