Pioglitazone hydrochloride (PGH) is an oral anti-hyperglycemic agent used in the treatment of type-2 diabetes mellitus. Potassium permanganate was found to oxidize PGH both in acidic and basic conditions, based on which two simple and sensitive methods were developed for its determination in bulk sample and tablets, and validated. In the first method (indirect method), PGH was reacted with a measured excess of standard permanganate in H₂SO₄ medium, and the residual oxidant was determined by measuring its absorbance at 550 nm. The second method (Direct method) entails treating PGH with permanganate in NaOH medium, followed by the measurement of the resulting bluish-green manganite at 610 nm. Experimental variables affecting the reactions were studied and optimized. Under optimum conditions, linear relationships with good correlation coefficients were found between absorbance and concentration in the ranges, 1.25 – 25 µg mL^-1 (Indirect method) and 1-12 µg mL^-1 (Direct method) with respective molar absorptivity values of 1.10 × 10⁴ and 2.77 × 10⁴ l mol^-1 cm^-1. The limits of detection (LOD) and quantification (LOQ) were 0.36 and 1.08 (Indirect method) and 0.23 and 0.69 µg mL^-1 (Direct method). Intra-day and inter-day precisions were satisfactory, with %RSD values of ≤2.11, and the respective accuracies were excellent with %RE values of ≤2. The methods were also validated for robustness, ruggedness and selectivity. The methods were applied to the determination of PGH in its tablets with good accuracy and precision, and no interference from the tablet additives was encountered. The results were also compared with those obtained by a reference method.

A highly sensitive, accurate and simple spectrophotometric method was established for determination of naproxen (NAP). The method involved ion-pair complex formation between naproxen and bromophenol blue (BPB). The colored product was measured at 432 nm. The reaction conditions were optimized. The absorbance was found to increase linearly with increase in concentration of NAP which was corroborated by correlation coefficient value. Beer’s law was obeyed in the concentration range of 1-110 µg mL-1 with molar absorptivity of 9.756×103 L mol-1 cm-1. The limits of detection (LOD) and quantitation (LOQ) for the proposed method are 0.292 and 0.973 µg mL-1, respectively. Recovery of the method was carried out by standard addition method. Recovery studies and statistical data proved the accuracy, reproducibility and the precision of the proposed method. The common excipients did not interfere in this analysis. Hence the method is useful for routine estimation of naproxen in pharmaceutical formulation and human serum samples.

In traditional spectrophotometric determination of stability constants of complexation, it is necessary to find a wavelength at which only one of the components has absorbance without any spectroscopic interference of the other reaction components. In the present work, a simple multi-wavelength model-based method has been developed to determine stability constants for complexation reaction regardless of the spectra overlapping of components. Also, pure spectra and concentration profiles of all components are extracted using multi-wavelength model based method. In the present work spectrophotometric titration of several cationic metal ions with new synthetic ligand were studied in order to calculate the formation constant(s). In order to estimate the formation constants a chemometrics method, model based analysis was applied.