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Facile and sensitive spectrophotometric methods for the determination of trace and ultra trace amounts of chromium (VI) are described. 4-aminoantipyrine (APP) reacts with 1-naphthol (NPL) in presence of oxidising agent potassium dichromate in acidic medium to produce red coloured product having λmaxof 485 nm. The molar absorptivity and Sandell's sensitivity were 2.07x104l mol-1cm-1and 0.00240 μg/cm2respectively. The colour is stable for more than 6 h. The system obeys Beer's law in the range, 2-18 μg for determination of chromium (VI). The detection limits of chromium (VI) is 0.048 μg mL-1. The method is highly reproducible and has been applied to the analysis of chromium in synthetic, natural water samples and pharmaceutical preparations and the results compared favourably with the reported method.

No abstract

A novel coupling reagent was used for simple, rapid, and sensitive spectrophotometric determination of isoniazid (1NH) and ritodrine hydrochloride (RTH) in pure form or in pharmaceutical preparations of it. The method is based on the diazotization of 4,4-methylene-bism -nitroaniline followed by a coupling reaction with either INH or RTH in hydrochloric acid medium. The resulting colored products have absorption maxima at 495 and 473 nm, respectively. Beer's law is obeyed in the concentration ranges of 0.1-15 µ g/mL and 0.1 − 17 µ g/mL. The method is applied for the analysis of INH/RTH in pharmaceutical preparations and the results agree favorably with the official and reported data. Common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity, and sensitivity without the need of extraction or heating.

A rapid, selective and sensitive spectrophotometric method for the determination of mosarpide in either pure form or in its formulations in pharmaceutical preparations is described. The method is based on the diazotization coupling reaction of mosapride with 1-naphthol in acidic medium to give red azo dye product with theλmaxof 500 nm and is stable for more than 12 hours at optimum condition, Beer's law is obeyed at concentration of 0.2 to 12 μg mL-1at the wavelength of maximum absorbance. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed method. The developed method is highly reproducible and applied to wide variety of pharmaceutical formulation and the results were compared favourably with the reported method.