Glycerol as a novel green mobile phase modifier for reversed phase liquid chromatography

Abstract

Introducing green organic solvents that can be used as mobile phase modifiers in liquid chromatography is crucial. The currently used modifiers are either expensive, less efficient, toxic or incompatible with UV detection. In this work, glycerol has been tried as a renewable cheap green solvent for mobile phase preparation in reversed phase liquid chromatography. The enthalpy–entropy calculations showed that analyte transfer from the glycerol-containing mobile phase to the stationary phase was favourable and exothermic. The thermodynamic calculation showed that the retention process was governed by partitioning rather adsorption. The high viscosity of glycerol could be manipulated by addition of water as a co-fluidizing solvent. The Van Deemter plot showed high efficiency using 7%glycerol, which could be due to the beneficial effects of glycerol on eddy and longitudinal diffusions. The mechanism of retention was studied by increasing the percentage of glycerol in the mobile phase and monitoring the change in retention. The observed decrease in retention with the increase in the mobile phase strength and the elution order of the more polar analytes first are typical for the reversed phase mode. The glycerol-containing mobile phase was successfully applied for separation of a mixture of four antiviral drugs using C18 column. The chromatographic conditions were optimized using factorial design. The mixture was separated in 13 min with acceptable resolution and peak shapes. The method was validated according to the ICH guidelines. Glycerol was found to be a promising green alternative for conventional mobile phase modifiers.