In this study, an environmentally friendly analysis of an anti-infective/anthelmintic drug thiabendazole was carried out by liquid chromatography method using ethanol solvent that is not harmful to human health and the environment. Protonation constant (Formula Presented) values of thiabendazole in 15, 20, 25, and 30% (v/v) ethanol-water binary mixtures at 37°C were obtained by using the green reverse phase liquid chromatography method. The method is based on a model that relates the chromatographic behavior of the determined analytes to pH. The linear relationship between the solvatochromic parameter (Formula Presented) and the retention values of the compound was determined depending on the variation " of the organic solvent in the mobile phase. The relationship between the calculated (Formula Presented) value and the macroscopic % properties of ethanol was investigated. Compatibility was observed between the (Formula Presented) values in the aqueous % medium determined by this linear approach. By using the (Formula Presented) value calculated for thiabendazole, the ionization percentages were calculated at different pH (1-12) values with the Henderson-Hasselbalch equation.