Micellar HPLC method using monolithic column for the simultaneous determination of linezolid and rifampicin in pharmaceuticals and biological fluids

A simple and rapid micellar liquid chromatographic method was developed and validated for the simultaneous determination of linezolid (LNZ) and rifampicin (RIF). The analysis was achieved using a 50 mm × 4.6 mm i.d., Chromolith® SpeedROD RP-18 endcapped column as the stationary phase. A mobile phase consisting of a mixture of 0.15 M sodium dodecyl sulphate (SDS), 0.3% triethylamine (TEA) and 10% n-propanol in 0.02 M orthophosphoric acid of pH 6.0 was pumped at a flow rate of 1 mL min−1, with ultraviolet detection at 254 nm. Lamotrigine (LTG) was used as an internal standard (IS). The method showed good linearity over the concentration ranges of 2.0–40.0 μg mL−1 and 6.0–120.0 μg mL−1 with limits of detection of 0.65 and 1.40 μg mL−1 and limits of quantification of 1.96 and 4.24 μg mL−1 for LNZ and RIF, respectively. The suggested method was successfully applied for the analysis of the studied drugs in their different dosage forms. The method was further extended to the determination of the studied drugs in spiked human plasma without prior extraction, the mean percentage recoveries in spiked human plasma (n = 4) were 99.94 ± 1.39 and 99.35 ± 4.15 for LNZ and RIF, respectively. Moreover the method was also extended to the in vitro determination of RIF in spiked human urine. Statistical evaluation and comparison of the data obtained by the proposed and comparison methods revealed good accuracy and precision of the proposed method.