Simple liquid chromatography–tandem mass spectrometry method for determination of novel anti-methicillin-resistant Staphylococcus aureus fluoroquinolone WCK 771 in human serum

A simple, rapid, specific, precise, accurate and sensitive method for determination of WCK 771 in human serum has been developed. The method uses high performance liquid chromatography with tandem mass spectrometric detection. Sample preparation involves protein precipitation method by addition of acetonitrile. Gatifloxacin was used as internal standard. The response was found to be linear from 0.312 to 40 μg/ml of serum with correlation coefficient greater than 0.99. Limit of detection and lower limit of quantification for WCK 771 was found to be 0.078 μg/ml and 0.312 μg/ml, respectively. The intra-day precision and accuracy from analysis of quality control (QC) samples at four concentrations was in the range of 2.36–2.58% and from 96.71 to 103.2%, respectively. The inter-day precision and accuracy from analysis of quality control samples at four concentrations was in the range of 3.14–6.82% and from 96.84 to 105.76%, respectively. WCK 771 was found to be stable for 24 h at auto-injector environment. WCK 771 was also found to be stable for 2 h in serum at 25 ± 3 °C and for 3 months at −20 °C. Mean absolute recovery at four different concentrations was 86.92% with standard deviation of 1.79. Throughput of the method is approximately one sample every 4 min. The method was also reproduced with monkey serum. The method was employed for estimation of drug serum levels during pre-clinical and clinical trials.