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Title: Application of bromate-bromide mixture and methyl orange in the titrimetric, spectrophotometric and kinetic assay methods for cyproheptadine in pharmaceuticals
Authors: Basavaiah, K
Keywords: Bromate-bromide mixture;Methyl orange;Cyproheptadine;Pharmaceuticals
Issue Date: Jul-2006
Publisher: CSIR
IPC Code: G01J3/00
Abstract: Three new methods have been developed for the assay of cyproheptadine in bulk drug and in tablet formulation based on the bromination of cyproheptadine hydrochloride (CPH) by bromine generated in situ by the action of acid on bromate-bromide mixture. In titrimetry, the drug is treated with a known excess of bromate-bromide mixture in hydrochloric acid medium followed by the determination of unreacted bromine iodometrically. Spectrophotometry involves the addition of a measured excess of bromate-bromide reagent in acid medium to CPH, and after the reaction is ensured to be complete, the residual bromine is determined by reacting with a fixed amount of methyl orange, and measuring the absorbance at 520 nm. In kinetic method, a mixture containing CPH and methyl orange dye in 1 M sulphuric acid is mixed with bromate-bromide reagent at 4-5°C and time required for bleaching of methyl orange colour is measured. In titrimetry and spectrophotometry, the amount of bromine reacted corresponds to the amount of CPH, and in the former method, quantitation is based on a 1:1 reaction stoichiometry (CPH:KBrO3) and the method is applicable over 2-15 mg range. The spectrophotometric method permits the determination of CPH in 0.5-4.0 μg mL-1 range with an apparent molar absorptivity of 5.25× 104 L mol-1 cm-1 and a Sandell sensitivity of 0.0062 μg cm-2. The limits of detection (LOD) and quantification (LOQ) are calculated to be 0.04 and 0.12 μg mL-1, respectively. Quantitation in kinetic method is based on the linear relationship that exists between the CPH concentration and the time for bromination as indicated by the bleaching of methyl orange acid color. The method is applicable over 10-50 μg mL-1 range with LOD and LOQ values being 1.42 and 4.74 μg mL-1 , respectively. The methods were statistically evaluated by calculating the relative error for accuracy and intra-day and inter-day coefficients of variation for precision, and were applied successfully to the determination of CPH in tablets and syrup with mean recoveries in the range of 97.58-100.9%. The accuracy and reliability of the methods were further ascertained by performing recovery tests via standard-addition technique. There was no interference from tablet excipients and additives.
Page(s): 360-366
ISSN: 0975-0991 (Online); 0971-457X (Print)
Appears in Collections:IJCT Vol.13(4) [July 2006]

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