A stability-indicating high-performance liquid chromatographic method was developed and validated for the determination of Letrozole in tablet dosage forms. Reversed-phase chromatography was performed on Shimadzu Model LC-Class-Vp with Lichrocart/Lichrosphere 100 C-18 (250 mm×4.6 mm, 5 μm particle size) column with methanol: tetra butyl ammonium hydrogen sulfate (80:20V/V) as mobile phase at a flow rate of 1 mL/min with UV detection at 240 nm. Linearity was observed in the concentration range of 0.5–150 μg/mL (R2=0.9998) with regression equation y=102582x+43185. The limit of quantitation (LOQ) and limit of detection (LOD) were found to be 0.043 and 0.012 μg/mL respectively. The forced degradation studies were performed by using HCl, NaOH, H2O2, thermal and UV radiation. Letrozole is more sensitive towards alkaline conditions and very much resistant towards acidic, oxidative and photolytic degradations. The method was validated as per ICH guidelines. The RSD for intra-day (0.78–0.97) and inter-day (0.86–0.96) precision were found to be lesser than 1%. The percentage recovery was in good agreement with the labeled amount in the pharmaceutical formulations and the method is simple, specific, precise and accurate for the determination of Letrozole in pharmaceutical formulations.

A reverse phase LC method was developed for the determination of Brimonidine in eye drops. Chromatography was carried on an Inertsil ODS 3V column (C18) using a mixture of Octane 1- sulfonic acid sodium salt (0.02M) (pH 3.5 ± 0.05) and acetonitrile (64:36 v/v) as mobile phase at a flow rate of 1 mL/min with UV detection at 254 nm. The drug was eluted at 4.636 min. The detector response was linear in the concentration range of 0.4–72 μg/mL. The limit of detection and limit of quantification were found to be 0.0561 and 0.1848 μg/mL respectively. The proposed method was validated as per the ICH guidelines and can be applied for the routine analysis of Brimonidine in eye drops.

A new, simple and sensitive spectrophotometric method in ultraviolet region has been developed for the determination of Bosentan in bulk and in pharmaceutical formulations. Bosentan exhibits absorption maxima at 273 nm with apparent molar absorptivity of 1.3293×104L/mol.cm in methanol and octane 1-sulfonic acid solvent mixture. Beer's law was found to be obeyed in the concentration range of 0.1-100 μg/mL. The method was validated as per the ICH guidelines.

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A reverse phase HPLC method is described for the determination of Dorzolamide in eye drops. Chromatography was carried on an Inertsil ODS 3V column using Acetonitrile : (0.02M) 1,Octane Sulphonic acid buffer (pH 3.5) (36:64 v/v) on isocratic mode at a flow rate of 1 mL/min with UV detection at 254 nm. The detector response was linear in the concentration range 4-720 µg/mL. The limit of detection and limit of quantification are found to be 0.7041 and 2.3483 µg/mL respectively. The method was validated as per the ICH guidelines. The proposed method is rapid, accurate and precise and can be applied for the routine analysis of dorzolamide in ophthalimic solutions.