Comparing HPLC and UV Spectrophotometric Analysis Methods for Determining the Stability of Sorbic Acid in Nonionic Creams Containing Lactic Acid

This paper describes a comparison between ultraviolet (UV) spectrophotometric and high-performance liquid chromatographic (HPLC) methods of analysis for the determination of sorbic acid in nonionic creams containing lactic acid. Sorbic acid is an antimycotic agent and is used as a preservative in pharmaceuticals, cosmetics, and food products. UV spectrophotometric analysis was done by calculating the concentration of remaining sorbic acid from the absorbance values and the molar extinction coefficient E258M = 24,080. A decrease in absorbance at 258 nm was accompanied by a simultaneous increase in total carbonyls and monoaldehyde content and the appearance of a very weak absorption maximum between 215 and 225 nm. HPLC analysis was done with a Hypersil BDS C8 column with detection at 254 nm and employing a mobile phase consisting of a mixture of buffer and methanol (7:3 v/v) at a pH of 2.25. The buffer consisted of 0.85% H2SO4 in 17.5 mM KH2PO4. The validation results, together with statistical treatment of...