REAL-TIME ANALYSIS BY MICRODIALYSIS-TANDEM MASS SPECTROMETRY(MD-MS/MS)

Abstract

Real-time analysis of R-84760 in blood was achieved by a combination of microdialysis (MD) and tandem mass spectrometry (MS/MS). With this technique, the analyte collected in real time from MD is separated by MS/MS, without any subsequent chromatographic separation. The R-84760 concentration was obtained from the plateau part of the ion intensities or the corrected values using an internal standard, after immersing the MD probe into the dialysis solution containing the drug for a definite time. Since contamination of the ion source was prevented by using an organic solvent for the perfused solution, it was possible to establish a stable analysis method. For a MD membrane of length 4 mm, the R-84760 concentration in saline was linear over the range 5 to 541.1 ng/ml (R²=0.9998). Moreover, the R-84760 concentration in rat whole blood was linear over the range 24.9 to 1868.9 ng/ml (R²=0.9995). As this method allowed the measurement of free drug concentration in rat blood, this analysis was also able to provide data needed for determining the protein-binding ratio. The protein-binding ratio obtained from the calibration curve in saline and rat whole blood was 87-90%, which was close to the result obtained by another analysis method. The concentration profile of R-84760 in blood as obtained by the MD-MS/MS method correlated well with the concentration profile in plasma, which was simultaneously monitored by LC-MS/MS.