Effect of tri-Potassium citrate on the Structure of Sucrose and Maltose in Solutions at Different Temperatures: Volumetric and Ultrasonic Studies

Abstract

A volumetric and sound velocity method was used for the analysis of effect of tri- Potassium citrate (TPC) on the structure of sucrose and maltose. Densities and sound velocities of sucrose and maltose in water and in aqueous 0.05 mol.kg-1, 0.20 mol.kg-1, 0.35 mol.kg-1 and 0.5 mol.kg-1 (TPC) solutions have been studied at 293.15K to 313.15K with an interval of 5K. From density values, various parameters such as apparent molar volume (φv), limiting apparent molar volume (φv 0), limiting apparent molar volume transfer (Δtrφv 0), apparent molar expansibilities (δφv 0/δT)p and Hepler’s constant have been calculated. The acoustic properties such as adiabatic compressibility (βs), apparent molar adiabatic compressibility (k), limiting apparent molar adiabatic compressibility (φk 0), apparent molar adiabatic compressibility of transfer (Δtrφk 0), acoustic impedance (Z) and hydration number (nH) have been calculated by densities sound velocities data. The densities increase with the increase of concentration of sucrose and maltose. Densities of sucrose and maltose in aqueous TPC solutions are higher than that of sucrose and maltose in pure water solution. The apparent molar volume varies upon the disaccharides (sucrose and maltose) concentration as well as on the temperature. The smaller values of experimental slope (Sv) as compared to limiting apparent molar volume (φv 0) values suggest the dominance of solute-solvent interaction over the solute-solute interaction. The true volume (φv 0) of disaccharides are found to be order of: maltose > sucrose. The limiting apparent molar volume transfer (Δtrφv 0) values of sucrose and maltose are positive which suggest the dominance of ion-hydrophilic and hydrophilic-hydrophilic interactions over the hydrophobic-hydrophobic and ion-hydrophobic interactions. The Δtrφv 0 values increase with an increase in concentration of the TPC which indicates the presence of strong ion-hydrophilic interactions in the mixtures. The values of limiting apparent molar volume expansion (δφv 0/δT)p are positive. Hepler’s constant values are positive or small negative for all studied disaccharides in binary and ternary system suggest the studied systems act as structure maker. The values of partial molar volumes (V2) increase with increasing of concentration of sucrose and maltose for the studied systems. The sound velocity increases with the increase of concentration of sucrose and maltose. Sound velocities of disaccharides in aqueous TPC solutions are higher than that of disaccharides in pure water solution. This indicate that the increase of compactness of the medium with the increase in disaccharides and TPC concentration. The adiabatic compressibility (βs) decreases with the increase of concentration of disaccharides. This indicates the water molecules around the disaccharides are less compressible than the water molecules in the bulk solution. The negative k values indicate the greater loss of structural compressibility of water. The positive Δtrφk 0 values for all the saccharides indicate the presence of ionic-hydrophilic and hydrophilic-hydrophilic interactions. The small Sk values also indicates the dominating of solute- solvent interactions over solutesolute interaction. The acoustic impedance, Z increases with the increase of concentration of disaccharides indicates the presence of effective solute-solvent interactions. The hydration number (nH) decrease with the increase of concentration and temperature for both binary and ternary systems. The positive hydration number (nH) values indicate an appreciable solvation of solutes. Hydration capacity of maltose is higher than sucrose in water and in aqueous TPC solution.