A fast and simple assay for busulfan in serum or plasma by liquid chromatography–tandem mass spectrometry using turbulent flow online extraction technology

Busulfan is used in myeloablative preparation regimens for hematopoietic bone marrow transplantation. Due to its narrow therapeutic range therapeutic drug monitoring of busulfan is recommended. In this study a fast and simple method for measuring busulfan in serum or plasma by liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed utilizing turbulent flow online extraction technology. Serum or plasma was mixed with acetonitrile containing d8-busulfan. After centrifugation the supernatant was injected onto a turbulent flow preparatory column then transferred to a C18 analytical column monitored by a tandem mass spectrometer set at positive electrospray ionization. The analytical cycle time was 4.0 min. The method was linear from 0.15 to 41.90 μmol/L with an accuracy of 87.9–103.0%. Inter- and intra-assay CVs across four concentration levels were 2.1–7.8%. No significant carryover or ion suppression was observed. No interference was observed from commercial control materials containing more than 100 compounds. Comparison with a well established LC–MS/MS method using patient specimens (n = 45) showed a mean bias 1.3% with Deming regression of slope 1.02, intercept −0.02 μmol/L, and a linear correlation coefficient 0.9883. The LC–MS/MS method coupled with turbulent flow online sample cleaning technology described here offers reliable busulfan quantitation in serum or plasma with minimum manual sample preparation and was fully validated for clinical use.