Spectrophotometric Determination of Urea in Dermatologic Formulations and Cosmetics

2008 Analytical Sciences  
A rapid, relatively sensitive, and low-cost method for the determination of water-soluble urea content in dermatological therapy products and cosmetics is proposed using a new spectrophotometric assay with water as the only extraction solvent. Spectrophotometric methods involve addition of a known excess of bromate to urea in an acid medium, followed by the determination of residual bromine and chlorine reacting with methyl orange and measurement of absorbance at 505 nm. The absorbance
more » ... linearly with urea concentration (r = 0.9998). The systems obey Beer's law for 6 -90 mg ml -1 . The calculated apparent molar absorbance values are found to be 4.537 ¥ 10 3 dm 3 mol -1 cm -1 and the Sandell's sensitivity is 0.013 mg cm -2 . The variables affecting the rate of the reaction were investigated. The relative standard deviation for five-replication determination of 60 mg ml -1 urea was 2.1% and the detection limit of the method is 0.34 ng ml -1 .
doi:10.2116/analsci.24.769 pmid:18544867 fatcat:oaxotjbehnavbdyx77gzoybnlu