Enantioselective LC/MS method for the determination of an antimalarial agent Fenozan B07 in dog plasma

A chiral liquid chromatography/mass spectrometry (LC/MS) bioanalytical procedure has been developed for the analysis of the antimalaric agent Fenozan B07 in dog plasma. Normal-phase chromatography involving a phenylcarbamate derivative of cellulose coated on silica gel as the chiral stationary phase was used to resolve (-)-(S,S)-B07 from (+)-(R,R)-B07. The enantiomers were detected by a mass spectrometer equipped with an atmospheric pressure chemical ionization (APCI) interface operated in the negative ion mode. A mass spectrum, characterized by a base peak of m/z 285, was obtained for each enantiomer. The m/z 285 ion was very specific for the analysis of both enantiomers in the plasma. The selected ion monitoring analysis of the plasma samples was therefore performed at m/z 285 for quantitative purposes. The enantiomers were extracted from the plasma in a basic medium and purified by solid-phase extraction using a hydrophilic-lipophilic balanced sorbent. A lower limit of quantification of 2 ng/mL in plasma was achieved for both enantiomers. The quantitative procedure reported in this study was highly specific and sensitive, and was validated according to the FDA guidance on bioanalytical method validation.