Simultaneous determination of busulphan in plasma samples by liquid chromatography-electrospray ionization mass spectrometry utilizing microextraction in packed syringe (MEPS) as on-line sample preparation method

Busulphan is an alkylating agent used in high doses as preparative regimen before stem cell transplantation (SCT). Busulphan has a narrow therapeutic window and under- or overdosing may have a fatal outcome for the patient. Therapeutic drug monitoring followed by dose adjustment is currently used to adjust the exposure to busulphan. This is an important issue to optimise and individualise high dose therapy with busulphan. However, this approach is limited to centres with experienced personal measuring busulphan plasma concentrations. An automated and easy-to-handle method for measurement of busulphan plasma concentrations may facilitate and wide-spread drug monitoring approach and thus improve the outcome of the patients undergoing SCT. Microextraction in packed syringe (MEPS) in combination with liquid chromatography and electrospray ionization mass spectrometric detection (LC-MS/LC-MS-MS) to quantify busulphan in human plasma samples without derivatization was developed. MEPS is a new miniaturised, solid-phase extraction technique that can be connected on-line to GC or LC without any modifications. In MEPS approximately 1 mg of the solid packing material is inserted into a syringe (100-250 mu L) as a plug. The validation of the method showed that the selectivity, accuracy and precision for the method were satisfactory. This is well in line with the international criteria for the study validation. The present method has shortened extraction time considerably and the method is fully automated, which benefits therapeutic drug monitoring of busulphan in SCT.