Solubility analysis of homologous series of amino acids and solvation energetics in aqueous potassium sulfate solution

Aslam Hossain,Kalachand Mahali,Bijoy Krishna Dolui,Partha Sarathi Guin,Sanjay Roy

doi:10.1016/j.heliyon.2019.e02304

Abstract

In this study we estimated the solubilities of glycine, D,L-alanine, D,L-nor-valine and D,L-serine in aqueous mixtures of potassium sulfate (K2SO4) at 298.15 K using analytical ‘gravimetric method’. The experimental solubilities of homologous series of amino acids in aqueous K2SO4 mixture were discussed in terms of relative solubility, salting-in and salting-out effect by evaluating the influential constants. The effect of physicochemical and chemical factors on solubility were discussed briefly and correlated with the thermodynamics. Initially, the study of solvation energetics such as transfer Gibbs energies were evaluated based on the calculations from solubility data and relative stability of the experimental molecules was discussed under the experimental condition.

Highlights

For quite a long time a significant attention has been made to study the thermodynamics of biologically important small molecules such as amino acids in dilute aqueous electrolyte solutions
We introduced our attention to find out the physicochemical and chemical factors associated with the solubility and the transfer Gibbs free energies and explained the relationship among solubility, solvation thermodynamics and stability of the studied amino acids in aqueous K2SO4 solution at 298.15 K
The mass of the dissolved amino acid in each 5 ml solution can be measured by knowing the amount of electrolyte in such solution (W1 g), weight of the empty glass vessel (W2 g), and glass vessel with dry sample (W3 g)

Summary

Introduction

For quite a long time a significant attention has been made to study the thermodynamics of biologically important small molecules such as amino acids in dilute aqueous electrolyte solutions It provides valuable information about the nature of the interactions between polar and nonpolar groups, water and aqueous electrolytes and contributes in understanding the chemistry of protein like complex systems in aqueous medium [1, 2, 3, 4, 5, 6]. D,L-serine contains a hydrophobic aliphatic hydrocarbon group (–CH2-) attached with one hydrophilic hydroxyl (–OH) moiety [Table 1] These structural differences may affect solvation factors which are very important for their separation from excess reagents and other impurities in aqueous solution. The solubility study of amino acids in the presence different electrolytes helps us to draw an idea in designing appropriate model for the purification of different amino acids

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Conclusion