The objective of the present work is to develop batch and merging-zone flow injection methods for sensitive and accurate spectrophotometric determination of tetracycline hydrochloride. The methods depend on the oxidation of the studied drug with potassium permanganate in an alkaline medium, and the absorbance of the green oxidation product was measured at 610 nm. The calibration graphs in both procedures were linear in the concentration ranges of 0.5 – 25 and 1 – 25 μg mL⁻¹ using the spectrophotometric and merging-zone flow injection methods, respectively. Specific and molar absorption coefficients, limits of detection and quantification, and Sandell’s sensitivity were calculated. The suggested procedures were further applied to the quantitative determination of tetracycline in pharmaceutical formulations.

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.