Simultaneous quantification of linezolid, rifampicin, levofloxacin, and moxifloxacin in human plasma using high-performance liquid chromatography with UV.

A high-performance liquid chromatography method with UV detection was developed and validated for the simultaneous quantification of linezolid (LZD), rifampicin (RFP), levofloxacin (LEVO), and moxifloxacin (MOXI) in human plasma. The method is based on a simple organic protein precipitation that guarantees rapid sample preparation and a direct injection into the high-performance liquid chromatography system. The use of quinoxaline as internal standard improved accuracy (relative standard deviation, RSD% <14.9%) and precision (RSD% <14.3%). The recovery was 75.9% (RSD% = 5.8). The limits of quantification were 0.234 microg/mL for LEVO, 0.312 microg/mL for LZD, 0.156 microg/mL for MOXI, and 0.622 microg/mL for RFP. This method allows the simultaneous measurement of LEVO, LZD, MOXI, and RFP in human plasma and may be used for both routine clinical applications and pharmacokinetic studies.