Nicotine aqueous solutions: pH-measurements and salting-out effects - analysis of the effective Gibbs energies of hydration and ionic strengths of the solutions

Abstract

This work is a continuation of our previous studies on the phase demixing - salting-out effects - in aqueous nicotine solutions. Thus, pH measurements were carried out allowing a brief analysis of the existing hydrogen bond interactions. Salting-out effects - the related experimental cloud point shifts - provoked by the addition of two inorganic salts, potassium nitrate and sodium sulfate, which were not studied so far, were determined. Analysis of the current and our previously reported salting-out/or salting-in phenomena in nicotine aqueous solutions was performed. In this respect, five studied salts were included: four inorganic salts (sodium chloride, potassium nitrate, sodium sulfate and sodium phosphate (Na3PO4)) and ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate ([C2mim][EtSO4] or ECOENG212?). Based on the pH measurements the effective Gibbs energies of hydration and ionic strengths of the respective ternary solutions were calculated and plotted against the related cloud-point shifts caused by the addition of the salts. For the studied salts, the results and diagram obtained within this work may be used to predict the cloud-points shifts, based on the related quantities of the salts added and/or the molar Gibbs energies of hydration and/or ionic strengths requested in each case.