QUANTITATION OF CREMOPHOR EL IN HUMAN PLASMA SAMPLES USING A COLORIMETRIC DYE-BINDING MICROASSAY

This paper describes an analytical procedure for the quantitative dete rmination of the pharmaceutical vehicle Cremophor EL in human plasma s amples. The procedure is based on rapid binding of Coomassie brilliant blue G-250 to Cremophor EL following plasma protein precipitation wit h acetonitrile and analyte extraction with n-butylchloride. The bindin g of the dye to Cremophor EL causes a shift in the absorption maximum from 465 to 624 nm, which is monitored using an automated microplate-a bsorbance reader. The assay permits estimation of Cremophor EL concent rations in the range 0.05-1.00% (v/v) in 50 mu L of human plasma, with percentage deviation and precision of less than or equal to 12 and le ss than or equal to 15%, respectively. The assay was subsequently used to measure Cremophor EL concentrations in plasma samples in support o f a project to develop a pharmacokinetic model for this compound in pa tients receiving paclitaxel. (C) 1998 Academic Press.