P-coumaric acid is a nonflavonoid phenolic acid and is a major constituent of the species Cynodon dactylon Linn. (Pers.). In this study isolation of P-coumaric acid was achieved by preparative TLC and the compound thus isolated was characterised by UV, mass, and H1 NMR spectral analysis. An isocratic RP-HPLC method was developed for the estimation of P-coumaric acid from methanolic extracts of durva grass. The chromatographic separations were achieved by RP-C18 column (250 mm × 4.6 mm, 5 μ), Shimadzu LC-20AT Prominence liquid chromatograph, and a mobile phase composed of water : methanol : glacial acetic acid (65 : 34 : 1 v/v). The flow rate was 1.0 mL/min and the analyses of column effluents were performed using UV-visible detector at 310 nm. Retention time of P-coumaric acid was found to be 6.617 min. This method has obeyed linearity over the concentration range of 2–10 μg/mL and the regression coefficient obtained from linearity plot for P-coumaric acid was found to be 0.999. RP-HPLC method was validated in pursuance of ICH guidelines.

A simple, specific, accurate, rapid, inexpensive isocratic Reversed Phase-High Performance Liquid Chromatography (RP-HPLC) method was developed and validated for the quantitative determination of Amlodipine besylate and Hydrochlorothiazide in pharmaceutical tablet dosage forms and HPLC method was used for an in vitro dissolution study of tablets containing the above drugs. RP-HPLC method was developed by using Welchrom C18 Column (4.6 X 250 mm, 5 µm), Shimadzu LC-20AT Prominence Liquid Chromatograph. The mobile phase composed of 10 mM Phosphate buffer (pH-3.0, adjusted with triethylamine): acetonitrile (50 : 50 v/v).The flow rate was set to 1.0 mL.min-1 with the responses measured at 230 nm using Shimadzu SPD-20A Prominence UV-Vis detector. The dissolution test was performed using 900 mL of distilled water as the dissolution media at 50 rpm using an USP Apparatus II at 37°C. The retention times of Hydrochlorothiazide and Amlodipine besylate were found to be 3.373 minutes and 3.753 minutes respectively. Linearity was established for Amlodipine besylate in the range of 1-5 µg / mL with correlation coefficient 0.9995 and Hydrochlorothiazide in the range of 3-15 µg / ml with correlation coefficient 0.9996. The validation of the developed method was carried out for specificity, linearity, precision, accuracy, robustness, limit of detection, limit of quantitation. The developed method can be used for routine quality control analysis of Amlodipine besylate and Hydrochlorothiazide in pharmaceutical tablet dosage form.