Spectrophotometric determination of salicylamide in pharmaceutical preparations Studies on analysis of mixed pharmaceutical preparations. V

• Published in: BUNSEKI KAGAKU Vol. 17; no. 4; pp. 475 - 478
• Main Authors: TATSUZAWA, Masayoshi, HASHIBA, Shigeko, NISHIMURA, Masao
• Format: Journal Article
• Language: Japanese; English
• Published: The Japan Society for Analytical Chemistry 1968
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.17.475

Salicylamide (I) reacts with dimethyl-p-phenylenediamine, and K3Fe (CN)6 in an alkaline medium (phosphate buffer : pH 8.0) to give green coloration (indophenol dye). This chromogen produced is extractable with chloroform, the extract showing an absorption maximum at 650mμ. A new spectrophotometric method, based on this color reaction, has been established to the determination of (I) in pharmaceutical preparations. Influences of 47 compounds were examined. The interferences from acetaminophene, ethoxybenzamide, salicylate, phenylephrine hydrochloride, sulpyrine, ascorbic acid, etc. are eliminated by the extraction with chloroform in an acidic medium. The recommended procedure is as follows. Sample {containing 100mg of (I)} is taken in a separatory funnel. To it are added 10ml of water and 10ml of 0.1 N HCl, and it is extracted 4 times with 30ml portions of chloroform. The extracts are combined and evaporated on a water bath. The residue is dissolved in 50ml of ethanol, and is made up exactly to 100ml with water. A 10ml aliquot is taken into another 100ml volumetric flask, and is made up to 100ml with ethanol. Ten ml of this solution is taken into another 100ml volumetric flask and prepared in the similar way. A 2 ml aliquot is transfered into a 30ml glass-stop-pered test tube. Five milliliters of buffer solution (phosphate buffer : pH 8.0), 2ml of 0.05% dimethyl-p-phenylenediamine solution and 1 ml of 1% K3Fe(CN)6 solution are added. After 5 min., the solution is shaken with 10ml of chloroform. The separated chloroform layer is dried with 2 g of Na2SO4, and is filtered. The absorbance is measured at 650mμ (ET) against chloroform. At the same time the absorbance of standard solution (ES) is determined, and the amount of (I) is calculated by ET/ES.