Determination of Celecoxib in human plasma using liquid chromatography with high resolution time of flight-mass spectrometry

A sensitive method for the determination of Celecoxib (CXB) in human plasma samples was developed using liquid chromatography coupled to electrospray ionization and time of flight mass spectrometry (LC–ESI–TOF–MS). A full factorial design of experiments (FF-DOE) methodology was applied to optimize the ESI conditions for CXB determination and also to predict the effects of interactions of multiple parameters affecting ionization (i.e., capillary voltage, fragmentor voltage, electrolyte and electrolyte concentration). The optimum ionization voltages were 4500 V and 220 V for capillary and fragmentor, respectively. Even though the highest ESI efficiency was obtained without electrolytes, the addition of 1.0 mM ammonium acetate was shown to be essential to buffer the matrix effect and ensure a consistent response. In contrast to previous studies, deuterated CXB was used as a recovery (surrogate) standard, which enabled the correction of CXB loss during sample preparation. The extraction recovery using solid phase extraction was 87–98%. The instrumental limit of detection of CXB (LOD), 0.33 ng/mL, and matrix affected LOD, 0.55 ng/mL, were similar and comparable to the previously reported LC–MS/MS LODs. This method was employed to determine CXB concentrations in human plasma samples. Upon administration of 400 mg CXB to the healthy women, the concentrations found in the plasma were 440–3300 ng/mL. The inter-day repeatability was less than 4% RSD.