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A selective, specific and stability-indicating gradient reverse phase high-performance liquid chromatographic (HPLC) method was developed for the determination of Ranitidine in presence of its impurities, forced degradation products and placebo substances such as saccharide and parabens. Ultraviolet detection was performed at 230 nm. Separate portions of the drug product and ingredients were exposed to stress conditions to induce oxidative, acidic, basic, hydrolytic, thermal and photolytic degradation. Ranitidine was found to degrade significantly at acidic, basic and oxidative stress conditions but was stable at heat and humidity. The developed method was validated as per International Conference on Harmonization (ICH) guidelines. The method was validated over this range for (i) system suitability (ii) specificity, (iii) precision, (iv) limit of detection and limit of quantification, (v) linearity, (vi) accuracy, (vii) robustness. The method was found to be precise, accurate, linear and robust. The proposed method was successfully employed for estimation of Ranitidine impurities in pharmaceutical preparations.

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A single RP-HPLC method is developed for estimation of isomeric impurities of vitamin D3 analogueCalcipotriol/Calcipotriene (Calci) and impurities of Betamethasone dipropionate (BD). The developed method is capable of separating impurities of Calci and BD, specifically pre-Calcipotriene (Pre-Calci) from other known and unknown impurities. Pre-Calci is isolated and is characterised using few analytical techniques. These impurities are separated using a RP-C18 150 × 4.6 mm, 2.7 µm column maintained at 50˚C. The mobile phase consisted of mixture of water, methanol, acetonitrile and tetrahydrofuran eluted in gradient mode. Detection was done at 264 nm and 240 nm for Calci and BD impurities respectively. The method can be used for determining quality of Calci and BD drugs and ointment based drug products. It is stability indicating related substance method for both the drugs and drug products.

A novel stability-indicating gradient reversed-phase ultra-performance liquid chromatographic (RP-UPLC) method was developed for the determination of purity of dorzolamide hydrochloride and timalol maleate in presence of their impurities, and forced degradation products and placebo. The method was developed using a Waters UPLC BEH C18, 100 × 2.1mm, 1.7 µm column with mobile phase containing a gradient mixture of solvents A and B. Phosphate buffer (0.04M), pH 2.6 was used as buffer. Buffer pH 2.6 was used as solvent A and Milli-Q water, methanol and acetonitrile in 200:300:600, v/v/v ratios were used as solvent B. The gradient program was set as 0/5, 8/8, 10/15, 16/45, 20/55, 24/80, 25/5 and 30/5. The eluted compound dorzolamide hydrochloride and its impurities were monitored at 254 nm, and timalol maleate and its impurities were monitored at 295 nm. The run time was 30 min, within which dorzolamide hydrochloride and its five impurities as well as timalol maleate and its three impurities were well separated, with resolution more than 2.0. Dorzolamide hydrochloride and timalol maleate were subjected to the stress conditions of oxidative, acid, base, photolytic and thermal degradation. The peak purity of dorzolamide hydrochloride, timalol maleate and their related compounds did not show any flag, thus proved the stability-indicating power of the method. The developed method was validated as per International Conference of Harmonization guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.