Simultaneous determination of ranitidine and metronidazole in human plasma using high performance liquid chromatography with diode array detection

The development and validation of a simple method for the simultaneous determination of ranitidine and metronidazole in human plasma is described. Plasma samples (250 μL) were deproteinized by precipitation with 60% perchloric acid, centrifuged and the supernatant directly injected into the HPLC. Separation was achieved in isocratic mode with a Shimpak C18 column and a mobile phase consisting of 10 mM potassium dihydrogen phosphate pH 3.5:acetonitrile (90:10, v/v) with UV detection at 315 nm. The method showed good selectivity and sensitivity. Good and consistent recovery for metronidazole and ranitidine was obtained: 96.22 ± 3.52 and 95.00 ± 4.50% for ranitidine (25-1000 ng/mL) and metronidazole (60-10,000 ng/mL), respectively (n = 3). With this one-step sample preparation method, both ranitidine and metronidazole could be quantified simultaneously in human plasma with good precision (R.S.D. < 15%) and accuracy (bias values below 15%). The limit of quantification for ranitidine and metronidazole were 20 and 40 ng/mL plasma, respectively.