Medicinski Podmladak (Jan 2020)
Examination of the influence of inorganic salts on the extraction of salicylic acid from aqueous solutions
Abstract
Introduction: Salicylic acid is a lipophilic compound with keratolytic and antiseptic effects. It is used only locally. The acid's fungicidal effect is notable in dermatology. Salicylic acid promotes desquamation of an infected area and represents an important ingredient of Whitfield's cream. Liquid-liquid extraction is often used during the sample preparation for the analyses of this type of compounds in various samples. Aim: The aim of this work was to investigate the effect of inorganic salts on the extraction of salicylic acid from aqueous solutions with diethyl ether. Material and methods: Extraction of salicylic acid from NaCl, KCl, and (NH4)2SO4 aqueous solutions of various concentrations was studied by using diethyl ether as an organic solvent. Absorbances of aqueous solutions were measured before and after extraction at the wavelength of the absorption maximum of the investigated compound. Results: The absorbance values of the aqueous phase prior to (A0) and after extraction (A) were used to calculate distribution coefficients (D) for the extraction of salicylic acid in the presence of different salts. Salting-out constants (Ks) for individual salts were determined based on the distribution constant dependence on salt concentration. Conclusion: It has been shown that all examined salts enhance the extraction of salicylic acid and the order of values for salting-out constants is: Ks((NH4)2SO4) > Ks(NaCl) > Ks(KCl). The results of this study may be important for improving the sensitivity of analytical methods for the salicylic acid determination in which extraction is used for sample preparation, as well as for the characterization of salicylic acid. Also, our work presents a contribution to the study of the salting-out effect which is significant for the characterization of pharmacologically active substances.
