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A simple and cost effective spectrophotometric method is described for the determination of torsemide in pure form and in pharmaceutical formulations. The method is based on the formation of blue colored chromogen when the drug reacts with Folin-Ciocalteu (F-C) reagent in alkaline medium. The colored species has an absorption maximum at 760 nm and obeys beer's law in the concentration range 30 – 150 ug mL−1. The absorbance was found to increase linearly with increasing concentration of TSM, which is corroborated by the calculated correlation coefficient value of 0.9999 (n=8). The apparent molar absorptivity and sandell sensitivity were 1.896×103 L mol−1 cm−1 and 0.183 μg cm−2, respectively. The slope and intercept of the equation of the regression line are 5.4x10−3 and 1.00×10−4 respectively. The limit of detection was 0.94.The optimum experimental parameters for the reaction have been studied. The validity of the described procedure was assessed. Statistical analysis of the results has been carried out revealing high accuracy and good precision. The proposed method was successfully applied to the determination of TSM in pharmaceutical formulations.

In this study, four simple, fast, accurate and sensitive spectrophotometric methods have been developed for the determination of gemifloxacin mesylate in pharmaceutical formulations. The methods are based on the charge transfer complexation reaction of the drug as n-electron donor with sigma (σ)-acceptor iodine, and the pi (π)-acceptors 2, 3-dichloro-5, 6-dicyano-p-benzoquinone (DDQ)-7,7,8,8-tetra cyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE). The obtained charge transfer complexes were measured at 290nm for iodine (in 1, 2-dichloro ethane), at 470, 840 and 420 nm for DDQ, TCNQ and TCNE (in acetonitrile), respectively. Optimization of different experimental conditions is described. Beer's law is obeyed in the concentration range of 6-30, 2-10, 2.5-12.5 and 1-5 μg mL−1 for iodine, DDQ, TCNQ and TCNE methods, respectively. The proposed methods were applied successfully to the determination of GFX in pharmaceutical formulations with good accuracy and precision.

Four simple and sensitive ion-pairing spectrophotometric methods have been described for the assay of gemifloxacin mesylate (GFX) either in pure form or in pharmaceutical formulations. The developed methods involve formation of colored chloroform extractable ion-pair complexes of the drug with safranin O (SFN O) and methylene blue (MB) in basic medium; Napthol blue 12BR (NB 12BR) and azocaramine G (AG) in acidic medium. The extracted complexes showed absorbance maxima at 525, 650, 620 and 540 nm for SFN O, MB, NB 12BR and AG, respectively.Beer's law is obeyed in the concentration ranges 3-15, 4-20, 2-10 and 2-10 μg/mL with molar absorptivity of 2.81 × 104, 2.20 x 104, 4.02 × 104 and 4.15 × 104 L mole−1 cm−1 and relative standard deviation of 0.077, 0.104, 0.080 and 0.103% for SFN O, MB, NB 12BR and AG, respectively. These methods have been successfully applied for the assay of drug in pharmaceutical formulations. No interference was observed from common pharmaceutical adjuvants. Results of analysis were validated statistically and through recovery studies.

Three simple, sensitive and cost effective Spectrophotometric methods are described for the determination of pitavastatin calcium (PST) in bulk drugs and in pharmaceutical formulations. These methods are based on the oxidation of PST by ferric chloride in presence of o-phenanthroline (Method A) or 2, 2’ bipyridyl (Method B) or potassium ferricyanide (Method C). The colored complex formed was measured at 510, 530 and 755 nm for method A, B and C respectively against the reagent blank prepared in the same manner. The optimum experimental parameters for the color production are selected. Beer’s law is valid with in a concentration range of 4-20 μg mL-1 for method A, 7.5-37.5 μg mL-1 for method B and 5 -25 μg mL-1 for method C. For more accurate results, ringbom optimum concentration ranges are 5-18 μg mL-1 for method A , 8.5-35.5 μg mL-1 for method B and 6.0-23.0 μg mL-1 for method C. The molar absorptivities are 3.55x104, 2.10x104 and 3.10x104 L mol-1 cm-1. Where as sandell sensitivities are 0.024, 0.041 and 0.028 μg cm-22 for method A, B and C respectively. The mean percentage recoveries are 99.95 for method A, 101.35 for method B and 100.33 for method C. The developed methods were applied for the determination of PST in bulk powder and in the pharmaceutical formulations without any interference from tablet excipients.

Two simple extractive Spectrophotometric methods are described for the determination of rosuvastatin calcium (RST) in pure form and in pharmaceutical formulations. These methods are based on the formation of ion association complexes of the RST with basic dyes safranin O (Method A) and methylene blue (Method B) in basic buffer of pH 9.8 followed by their extraction in chloroform. The absorbance of the chloroform layer for each method was measured at its appropriate λmax against the reagent blank. These methods have been statistically evaluated and are found to be precise and accurate.