TLC-densitometric identification of valproic acid

Abstract

Valproic acid and its derivatives are drugs that have been used in many neurogenic diseases, but are mainly used in epileptic seizures. Due to the fact that valproic acid doesn’t have conjugated double bonds, it isn’t visible under UV light and its detection is difficult. Therefore, the aim of the study was to assess the suitability of individual visualizing reagents in the chemical qualitative and quantitative detection of valproic acid using the TLC technique. Solutions of various visualizing reagents were prepared, and then the reagents were applied on the previously prepared chromatographic plates with valproic acid by means of an immersion and spraying method in order to detect it. It was shown that all the visualizing reagents used, with the exception of helasol green, bromothymol blue, malachite green, bromocresol green in 2% sodium hydroxide solution and sulphate (VI) solutions of iron (II), nickel and cobalt, allowed for the qualitative detection of valproic acid. It is recommended to use a 1% solution of copper (II) sulphate (VI) for the detection of valproic acid for both qualitative and quantitative purposes, due to the largest areas of the chromatographic bands on most of the chromatographic plates used in the study. There is a potential possibility of examining the identity of valproic acid present in drugs on the basis of the RF value, the characteristic colour of the spot, and a comparative analysis of spectrodensitograms.