Gas chromatographic-mass spectrometric method for quantitative determination of ketotifen in human plasma after enzyme hydrolysis of conjugated ketotifen.

A validated method for determination of total amount of ketotifen (unchanged and conjugated) in human plasma has been presented. An enzyme hydrolysis of conjugated ketotifen was conducted with combination of beta-glucuronidase and arylsulfatase. After the enzyme hydrolysis a solid-phase extraction was applied as a cleaning step. The quantitative determination by gas chromatography with mass-spectrometry detection (GC-MS) was performed. Pizotifen has been used as an internal standard. A reliable hydrolysis as well as a satisfactory accuracy, improved precision in the linear region from 0.500 to 10.0 ng/ml plasma, limit of detection of 0.010 ng/ml and prolonged capillary column life have been achieved.