Ultraviolet (UV), first derivative, second derivative, and AUC-spectrophotometric methods for the determination of letrozole in pharmaceutical formulations have been developed. For UV-spectrophotometry, the standard solutions were measured at 240.0 nm. The linearity ranges were found to be 0.25–20.0 μgml–1 in methanol and the regression equation was A=1.20×10–1C+2.22×10–2(r2=0.9994). For the first derivative spectrophotometry, the response (dA/dλ) of standard solutions was measured at 224.0 nm. The calibration curve was constructed by plotting dA/dλ values against concentrations 0.25–20.0 μgml–1, of letrozole. The regression equation of the linear calibration graph was calculated as D1=3.89×10–3C+1.85×10–4(r2=0.9987). For the second derivative spectrophotometry, the response (d2A/dλ2) of standard solutions was measured at 241.0 nm. The calibration curve was constructed by plotting d2A/dλ2 values against concentrations 0.5–20.0 μgml–1 of letrozole standards in methanol. The regression equation of the linear calibration graph was calculated as D2=-1.59×10–3C-4.66×10–4(r2=0.9985). The AUC-spectrophotometric method was based on the calculation of Area under Curve (AUC), for analysis of letrozole in the wavelength range of 235.0–245.0 nm. The calibration curve was constructed by plotting AUC values against concentrations 0.25–20.0 μgml–1, of letrozole. The regression equation of the linear calibration graph was calculated as AUC=1.132C+0.2153 (r2=0.9994). The methods were validated by following the analytical performance parameters suggested by the International Conference on Harmonization (ICH). All validation parameters were within the acceptable range. The developed methods were successfully applied to estimate the amount of letrozole in pharmaceutical formulations.

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.

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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.

An isocratic RP-HPLC method was developed for the determination of Cefditoren pivoxil in pharmaceutical formulations using a C-18 column with water–acetonitrile (50:50, v/v) as mobile phase and flow rate 1.2 mL/min (UV detection at 218 nm). Linearity was observed in the concentration range 1.0–250 μg/mL (R2=0.999) with regression equation y=24194x+10749. The forced degradation studies were performed by using HCl, NaOH, and H2O2, and thermal and UV radiation. Cefditoren pivoxil is more sensitive towards oxidation and alkaline conditions and resistant towards acidic and photolytic degradations. The method was validated as per ICH guidelines.