A new, simple and sensitive spectrophotometric method for the determination of catechol and resorcinol has been developed. The method is based on the reaction of catechol and resorcinol with2,4-di nitrophenyl hydrazine to yield orange-colored products respectively. catechol and resorcinol showed maximum absorbance at385 nm and 404nm with linearity was observed in the concentration range of (1-40 µg/mL) for catechol, and (1-25 µg/mL) for resorcinol with correlation coefficient (0.9982) for both compounds, Sandell's sensitivity 0.0216 (μg cm -2 ) and 0.025 (μg cm -2 ) respectively.
Loperamide hydrochloride (LopH) has been determined by oxidative -coupling reaction using phenothiazine reagent in the presence of potassium dichromate as an oxidant to create a greenish-blue soluble complex measured at 625 nm., linearity range is from0.8 to 40 µg.ml -1 of LopH. The molar absorptivity is 0.3799×10 4 l.mol -1 .cm -1 , Sandell's sensitivity is 0.1351µg cm -2, limit of detection and limit of quantitation are 0.33918, and 1.1306 µg.ml -1 respectively. The method is new ,simple, sensitive and it has been applied successfully for determination of LopH in pharmaceutical preparation of three dosage forms of LopH; Loperamide 2 mg/tablets Medochemie Ltd, Limassol-Cyprus (Europe), Loperamide 2 mg/tablets Safa Co. -Diala (Iraq) and Loperamide 2 mg/capsules Janssen pharmaceuticals (Belgium).
A simple, rapid and sensitive spectrophotometric method has been developed for the determination of captopril in aqueous solution. The method is based on reaction of captopril with 2,3-dichloro 1,4- naphthoquinon(Dichlone) in neutral medium to form a stable yellow colored product which shows maximum absorption at 347 nm with molar absorptivity of 5.6 ×103 L.mole-1. cm-1. The proposed method is applied successfully for determination of captopril in commercial pharmaceutical tablets.
A sensitive, accurate and easy indirect spectrophotometric method was developed for the determination of mesalazine in its pure form and in pharmaceutical preparations (tablets, capsules). The method was based on the oxidation of the mixture of the drug compound with the hydralazine reagent by using the oxidizing agent potassium periodate in an acidic medium and in the presence of the surfactant triton (x-100), absorption was measured at 380 nm for the drug compound, and the molar absorbance of mesalazine was 1147.5 liters. Mol-1. cm-1. With a recovery rate of 99.38, the method was developed to be simple, inexpensive and fast because it does not include any solvent extraction. The method has been successfully applied to pharmaceutical preparations.
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