Rapid determination of ranitidine in human plasma by high-performance liquid chromatography without solvent extraction

A simple high-performance liquid chromatographic procedure was developed for the determination of ranitidine in human plasma. The method entailed direct injection of the plasma samples after deproteination using perchloric acid. The chromatographic separation was accomplished with an isocratic elution using mobile phase consisting of 21 mM disodium hydrogen phosphate-triethylamine-acetonitrile (1000:60:150, v/v), pH 3.5. Analyses were run at a flow-rate of 1.3 ml/min using a microbondapak C18 column and ultraviolet detection at a wavelength of 320 nm. The method was specific and sensitive, with a quantification limit of approximately 20 ng/ml and a detection limit of 5 ng/ml at a signal-to-noise ratio of 3:1. The mean absolute recovery was about 96%, while the within- and between-day coefficient of variation and percent error values of the assay method were all less than 8%. The linearity was assessed in the range of 20-1000 ng/ml plasma, with a correlation coefficient of greater than 0.999. This method has been used to analyze several hundred human plasma samples for bioavailability studies.