DETERMINATION OF THE ENANTIOMERS OF IFOSFAMIDE AND ITS 2-N-DECHLOROETHYL-ATED AND 3-N-DECHLOROETHYLATED METABOLITES IN PLASMA AND URINE USING ENANTIOSELECTIVE GAS-CHROMATOGRAPHY WITH MASS-SPECTROMETRIC DETECTION

A rapid, sensitive, enantioselective gas chromatographic method has be en developed for the quantitation of the enantiomers of ifosfamide (IF F) and its 2- and 3-dechloroethylated metabolites (2-DCE-IFF and 3-DCE -IFF) in human and animal plasma and human urine. IFF and the two dech loroethylated metabolites were extracted into chloroform, enantioselec tively resolved by gas chromatography on a chiral stationary phase bas ed upon heptakis(2,6-di-O -methyl-3-O-pentyl)-beta-cyclodextrin and qu antitated using mass-selective detection with selected-ion monitoring. The limits of quantitation for the enantiomers of IFF, 2-DCE-IFF and 3-DCE-IFF in plasma were 250 and 500 ng/ml respectively. In urine, the limits of quantitation for the enantiomers of IFF, 2-DCE-IFF and 3-DC E-IFF were 500 ng/ml. The method can detect concentrations as low as 2 50 ng/ml of each enantiomer of 2- and 3-DCE-IFF in plasma and urine. T he intra- and inter-day coefficients of variation for this method were with one exception less than 8%. The assay was validated for enantios elective pharmacokinetic studies in humans and rats and is the first r eported enantioselective assay for the measurement of the enantiomers of 2- and 3-DCE-IFF in plasma.