Determination of the enantiomers of salbutamol and its 4-O-sulphate metabolites in biological matrices by chiral liquid chromatography tandem mass spectrometry.

Sensitive, mass spectrometry based bioanalytical methods are described for the determination of the R- and S-enantiomers of the beta-agonist salbutamol (albuterol) and its 4-O-sulphate metabolite in human plasma and urine. In both methods samples are prepared by 96 well format solid phase extraction using a custom built robotic system. Extracts are then analysed by liquid chromatography tandem mass spectrometry (LC-MS/MS) using a teicoplanin-based chiral stationary phase and selected reaction monitoring. The methods are accurate (bias < +/- 10%), precise (%CV < 11%) and sensitive, providing lower limits of quantitation (LLoQ) in plasma of 100 pg/mL and 5 ng/mL for the enantiomers of salbutamol and its 4-O-sulphate metabolite, respectively. By restricting the chiral method for plasma to the enantiomers of salbutamol only, it was possible to revalidate at an improved LLoQ of 25 pg/mL. A high throughout LC-MS/MS method has also been developed for racemic salbutamol only, which uses a similar extraction procedure but a conventional C8 column. The method has a reduced analysis time of three minutes per sample and using a high sensitivity, triple quadrupole mass spectrometer provides an LLoQ of 5 pg/mL based on extraction of 0.5 mL of plasma.

Determination of the glucocorticoid fluticasone propionate in plasma by automated solid-phase extraction and liquid chromatography-tandem mass spectrometry.

A sensitive, robust and high throughput mass spectrometry based method is described for the determination of the glucocorticoid fluticasone propionate in plasma. The method employs solid-phase extraction in 96 well microtitre plate format which has been automated by means of a custom built Zymark robotic system. The extracts are analysed by liquid chromatography-tandem mass spectrometry using thermally and pneumatically assisted electrospray ionisation and selected reaction monitoring. The method is both accurate and precise with both intra- and inter-assay precision (C.V.) of less than <6%. The method provides a lower limit of quantification of 20 pg/ml from 0.5 ml of human plasma, sufficient to monitor systemic concentrations of inhaled fluticasone propionate at therapeutic doses.