A rapid, simple and sensitive high-performance liquid chromatographic (HPLC) method for determination of Amlodipine (AML) using sodium 1,2-naphthoquinone-4-sulfonate (NQS) has been developed. The method is based on the formation of a brown color product from the reaction between AML and NQS. The nucleophilic substitution reaction proceeds quantitatively at pH 13 buffer solution with absorption maximum at 465 nm. A C 18 column ODS (250mm×4.6mm), 5μm and a mobile phase of combination is potassium dihydrogen orthophosphate (0.05M) in water: acetonitrile (45:55%v/v) were used for separation and quantification. Analyses were run at a flowrate of 1.5mL/min and at 40 °C temperature. The injection volume was 20μL and the photodiode array detector was set at 465nm. Under these conditions Amlodipine-NQS eluted at 3.12 min. Total run time was shorter than 5 min. The developed method was validated according to the literature and found to be linear within the range 2-30μg /mL, describes by the regression equation y =207,082x +1,481.71 with a regression coefficient 0.999. The limit of detection and quantity are 0.01μg/mL and 0.04μg∕ mL respectively. This method is simple and can be applied for the determination of AML in pharmaceutical formulation in quality control laboratories.

A rapid, simple and sensitive high-performance liquid chromatographic (HPLC) method for determination of Amlodipine (AML) using sodium 1,2-naphthoquinone-4-sulfonate (NQS) has been developed. The method is based on the formation of a brown color product from the reaction between AML and NQS. The nucleophilic substitution reaction proceeds quantitatively at pH 13 buffer solution with absorption maximum at 465 nm. A C 18 column ODS (250mm×4.6mm), 5μm and a mobile phase of combination is potassium dihydrogen orthophosphate (0.05M) in water: acetonitrile (45:55%v/v) were used for separation and quantification. Analyses were run at a flowrate of 1.5mL/min and at 40 °C temperature. The injection volume was 20μL and the photodiode array detector was set at 465nm. Under these conditions Amlodipine-NQS eluted at 3.12 min. Total run time was shorter than 5 min. The developed method was validated according to the literature and found to be linear within the range 2-30μg /mL, describes by the regression equation y =207,082x +1,481.71 with a regression coefficient 0.999. The limit of detection and quantity are 0.01μg/mL and 0.04μg∕ mL respectively. This method is simple and can be applied for the determination of AML in pharmaceutical formulation in quality control laboratories.

A simple, specific, accurate and precise, stability indicating HPLC method for the simultaneous determination of antihypertensive drug combination consisting of amlodipine (AML), hydrochlorothiazide (HCT) and valsartan (VAL) was developed and validated. The optimized conditions for the separation of the three analytes was consisted of ODS C-18 (250mm×4.6mm i.d. 5μm) column, mobile phase: acetonitrile-potassium dihydrogen phosphate pH 3. 5-acetonitrile (45:55% v/v). Column temperature was maintained at 40oC; mobile phase flow rate: 1.5mL/ min; wave length : 230 nm; and injection of 20μL. The precision of the method was measured through adequate repeatability or intraday precision (RSD ≤ 2) and interday precision (RSD ≤ 2). The method demonstrated adequate linearity of detector response over the range of 0.5-250%. The limits of detection for AML, HCT and VAL were 0.011, 0.010 and 0.010µg/mL, while the limits of quantification were 0.032, 0.020 and 0.019µg/mL respectively. The method also showed adequate robustness to variations in mobile phase, pH, and column temperature and acetonitrile concentrations. The full recoveries of each working standard for all compounds were within ICH specifications of 98-101% which showed that the method was accurate. The proposed method proved to be stability indicating by resolution of the analytes from their accelerated storage conditions products. The developed method is rapid (run time 8min), selective, requires simple sample preparation procedures and simple mobile phase combinations. It is also cost effective and represents a good procedure for determination of AML, HCT and VAL in bulk raw materials and pharmaceutical dosage forms. Figure 1C). KeywordsLiterature survey revealed that a number of methods have been reported for estimation of AML, HCT and VAL individually or in combination with other drugs. However, there is very few analytical methods reported for the simultaneous analysis of these drugs in a combined dosage formulation. The reported methods are UV spectrophotometric [7][8][9][10][11][12] Stability testing is an important issue in the process of drug product development. The purpose of stability testing is to provide evidence on how the quality of a drug substance or drug product varies with time under the influence of a variety of environmental factors, such as temperature, humidity, and light, and enables recommendation of storage conditions, retest periods, and shelf lives to be established. The two main aspects of a drug product that play an important role in shelf life determination are assay of the active drug and degradation products generated during the stability study. The drug product in a stability test sample needs to be determined using a stability indicating method, as recommended by the International Conference on Harmonization (ICH) guidelines [33] and U.S. Pharmacopia (USP) [34]. Although stability indicating methods have been reported for assay of various drugs in drug products, most of them describe assay procedures for drug products c...