Evaluation of Purity of some Coumarin Derivatives by Melting Point Measurments, TLC and Scanning Densitometry

Abstract

Impurity remains after syntheses greatly influence properties and effectiveness of synthesized compounds. Therefore it is very important to determine its presence and remove them from the synthesized product. In order to obtain crystals of high purity, synthesized bis-4-hydroxycoumarins and benzopyranocoumarins were purified by recrystallization and column chromatography. The success of the purification of the synthesized compounds was examined by the melting point measurements, thin layer chromatography and scanning densitometry. Only one of nine tested mobile phase systems proved successful for separation of the analyzed compounds. Detection of the compounds on TLC plates was carried out under UV light at wavelength of 254 nm, as well as quantitative analysis of the present impurities. The results of scanning densitometry showed that the corresponding compounds obtained by purification had a satisfactory degree of purity (less then 2% unknown impurities). Percentage of impurities can also be calculated from data attained by spectrometric methods and elemental analysis.