Simultaneous high-performance liquid chromatographic determination of atenolol and amlodipine in pharmaceutical-dosage form.

A simple, rapid and precise method is developed for the quantitative simultaneous determination of atenolol and amlodipine in a combined pharmaceutical-dosage form. The method is based on High Performance Liquid Chromatography (HPLC) on a reversed-phase column, shim-pack CLC, ODS (C18), 4.6 mmx25 cm & 0.5 mm, using a mobile phase of ammonium acetate buffer (the pH was adjusted to 4.5+/-0.05 with glacial acetic acid), acetonitrile and methanol (35::30:35 v/v). The buffer used in the mobile phase contains ammonium acetate in double-distilled water. The chromatographic conditions are- flow rate of 1.5 ml/min, column temperature at 40 degrees C and detector wavelength of 237 nm. Both the drugs were well resolved on the stationary phase and the retention times were around 1.5 minute for atenolol and 3.4 minute for amlodipine. The method was validated and shown to be linear for atenolol and amlodipine. The correlation coefficients for atenolol and amlodipine are 0.999963 and 0.999979, respectively. The relative standard deviations for six replicate measurements in two sets of each drug in the tablets is always less than 2% and mean % error of active recovery not more than +/-1.5%. The method was validated for precision and accuracy. The proposed method was successfully applied to the pharmaceutical dosage forms containing the above-mentioned drug combination without any interference by the excipients.