Development of a fast and simple liquid chromatography–tandem mass spectrometry method for the quantitation of argatroban in patient plasma samples

An ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method for the direct measurement of argatroban in human plasma was developed and compared with the activity-based Hemoclot Thrombin Inhibitors assay. UPLC–MS/MS was performed using diclofenac as an internal standard. In summary, argatroban and diclofenac were extracted from 100 μL of plasma using a methanol precipitation protocol, and chromatographic separation was performed on an ACQUITY™ TQD mass spectrometer using a UPLC C18 BEH 1.7 μm column with a water and methanol gradient containing 0.1% formic acid. The detection and quantitation were performed using positive ion electrospray ionization and multiple reaction monitoring (MRM) mode. The UPLC–MS/MS method was linear over the concentration range of 0.003–3.0 μg/mL, with a lower limit of quantitation for argatroban of 0.003 μg/mL. The intra- and inter-assay imprecision was less than 12% at the plasma argatroban concentrations tested. Good correlation was demonstrated between the UPLC–MS/MS method and the indirect activity-based assay for determination of argatroban. However, increased plasma fibrinogen levels caused underestimation of argatroban levels using the indirect activity-based assay, whereas the UPLC–MS/MS method was unaffected. UPLC–MS/MS provides a relatively simple, sensitive, and rapid means of argatroban monitoring. It has successfully been applied to assess plasma argatroban concentrations in hospitalized patients and may provide a more accurate determination of argatroban concentrations than an activity-based assay in certain clinical conditions.