Improvement of determination method of Metronidazole in human plasma

OBJECTIVE To improve the RP-HPLC method for the determination of metronidazole in human plasma.METHODS Phenomenex C18 column(150 mm × 4.6 mm,5 μm) was used.The mobile phase was methanol-water(25:75) at a flow rate of 1 mL·min-1.Both metronidazole and tinidazole(internal standard) were extracted from 500 μL plasma sample alkalinized by borax buffer(pH9.5) with dichloromethane-acetoacetate(1:1).After evaporation of the organic layer,the residue was dissolved in 50 μL mobile phase,then 20 μL was injected.The detective wavelength was 320 nm.RESULTS The retention time for metronidazole and tinidazole were 4.0 min and 4.8 min,respectively.Standard curve was linear in the concentration range from 0.0125 to 20 μg· mL-1.Lower limit of quantitation was 0.0125 μg·mL-1.The RSD of intra-and inter-day precision was less than 7%.The method recovery was 95.67%-108.21%.The extraction recovery was 70.25%-77.76%.CONCLUSION This method is simple,rapid,sensitive and accurate for determination of metronidazole in human plasma.