A stability-indicating liquid chromatographic method has been developed and validated for the determination of Diltiazem Hydrochloride (DTZ) together with its six related substances (Diltiazem sulphoxide,Imp-A,Imp-B,Imp-D,Imp-E,and Imp-F) in a laboratory mixture as well as in a novel tablet formulation developed in-house.Efficient chromatographic separation was achieved on a Hypersil BDS C18 (150mm ×4.6mm,5.0μm) with mobile phase containing 0.2％ Triethylamine (TEA) in gradient combination with acetonitrile (ACN) at a flow rate of 1.0 mL/min and the eluent was monitored at 240 nm.In the developed method,the resolution of DTZ from any pair of impurities was found to be greater than 2.0.The test solution and related substances were found to be stable in the diluent for 24 h.The developed method resolved the drug from its known impurities,stated above,and also from additional impurities generated when the formulation was subjected to forced degradation; the mass balance was found close to 99.9％.Regression analyses indicate correlation coefficient value greater than 0.997 for DTZ and its six known impurities.The LOD for DTZ and the known impurities was at a level below 0.02％.The method has shown good,consistent recoveries for DTZ (99.8-101.2％) and also for its six known impurities (97.2-101.3％).The method was found to be accurate,precise,linear,specific,sensitive,rugged,robust,and stability-indicating.

Acitretin is a photosensitive oral retinoid with very limited data available on its degradation. The official HPLC method for acitretin determination was insufficient to resolve the degradation products generated during stability studies. Therefore, an isocratic RP-HPLC-UV method was developed for the determination of acitretin in the presence of its related impurities and degradation products. Efficient chromatographic separation was achieved on a Thermo beta-basic column C18 (100 mm×4.6 mm, 5 μm) with mobile phase containing 0.3% (v/v) glacial acetic acid with acetonitrile (ACN) and isopropyl alcohol (IPA) in an isocratic ratio of 70:30 at a flow rate of 1.0 mL/min with the eluent monitored at 360 nm. The method was validated for specificity, linearity, precision, accuracy and robustness. The calibration plot was linear over the concentration range of 50-150 μg/mL with a correlation coefficient (r (2)) of 0.999. The proposed method was used to investigate the degradation kinetics of acitretin under the different degradative conditions. The degradation rate constant (K), half-life (t 1/2), and t 90 were calculated. Degradation of acitretin followed pseudo-first-order kinetics. The drug was found to be less stable under acidic and photolytic degradation conditions: the photolytic degradation constants for acitretin in sunlight and UV light were 0.002698% and 0.0008402% min(-1), respectively. The LOD for acitretin and the known impurities were at a level below 0.02%. The method shows consistent recoveries for ACTR (99.8%-101.2%) and also for its known impurities (97.2-101.3%). The method was found to be accurate, precise, linear, specific, sensitive, rugged, robust, and useful for characterizing the stability of this chemical.