Quantification of voriconazole in plasma by liquid chromatography-tandem mass spectrometry.

A convenient liquid chromatography-tandem mass spectrometry method for the quantification of the triazole antifungal agent voriconazole in plasma samples is described. Fenbuconazole is used as an internal standard. After protein precipitation, automated solid-phase extraction is applied. Electrospray ionization in the positive mode is used and the following mass transitions are recorded: voriconazole, 350-->127; and fenbuconazol, 337-->125. The analytical run time is 4 min. The response was linear from 78 to 5000 microg/L. The total coefficient of variation (n=16) was 12.6% for a low-concentration pool (143 microg/L), 4.7% for a medium-concentration pool (419 microg/L), and 5.0% for a high-concentration pool (4304 microg/L). The method is proposed for future investigations that should be performed to test the hypothesis that therapeutic drug monitoring of voriconazole is clinically useful.