Simultaneous determination of the enantiomers of leucine and [~2H_7]leucine in plasma by capillary gas chromatography-mass spectrometry

摘要

A method for the stereoselective assay of D- and L-enantiomers of both leucine and [~2H_3]leucine was used as an internal standard.The method involved purification by cation-exchange chromatography using BondElut SCX cartridge and derivatization with hydrochloric acid in methanol to form methyl ester followed by subsequent chiral derivatization with (+)-#alpha#-methoxy-#alpha#-trifuoromethylphenylacetyl chloride to form diastereomeric amide.The derivatization made the separation of the leucine enantiomers possible with good gas chromatographic behavior.Quantitation was performed by selected-ion monitoring of the quasi-molecular ions of the diastereomers on the chemical ionization method.The sensitivity,specificity,accuracy and reprodibility of the method were demonstrated to be satisfactory for application to pharmacokinetic studies of leucine enantiomers.