Validation of a novel LC-MS/MS method for the quantitation of colistin A and B in human plasma.
A sensitive method has been developed and validated, using LC/ESI-MS/MS, for simultaneous quantitation of flupentixol and melitracen-antidepressant drugs, in human plasma. The quantitation of the target compounds was determined in a positive ion mode and multiple reaction monitoring (MRM). The method involved a repeated liquid-liquid extraction with diethyl ether and analytes were chromatographed on a C(8) chromatographic column by elution with acetonitrile-water-formic acid (36:64:1, v/v/v) and analyzed by tandem mass spectrometry. The method was validated over the concentration ranges of 26.1-2090 pg/ml for flupentixol and 0.206-4120 ng/ml for melitracen. The correlation coefficients of both analyst were >0.998 for six sets of calibration curves. The recovery was 60.9-75.1% for flupentixol, melitracen and internal standard. The lower limit of quantitation (LLOQ) detection was 26.1 pg/ml for flupentixol and 0.206 ng/ml for melitracen. Intra- and inter-day precision of the assay at three concentrations were 2.15-5.92% with accuracy of 97.6-103.0% for flupentixol and 0.5-6.36% with accuracy of 98.7-101.7% for melitracen. Stability of compounds was established in a battery of stability studies, i.e., bench-top, autosampler and long-term storage stability as well as freeze/thaw cycles. The method proved to be suitable for bioequivalence study of flupentixol and melitracen in healthy human male volunteers.