Physicochemical studies on vitamins B1, B3, B6 and C in aqueous magnesium chloride solutions at different temperatures (288.15–318.15) K and at pressure (101.3) kPa

Abstract

Vitamins are the precursors of many coenzymes essential for biocatalysts and their deficiency leads to diseases in masses. The vitamins are very fragile and can easily be destroyed with change external atmosphere. Electrolytes are inherent constituents of cytoplasm and are required in variety of biochemical functions. The interactions occurring between, solute-cosolute and solvent can be inferenced and interpreted from thermodynamic and transport studies effectively which will help in interpreting the mechanism of vitamins in solution phase. In the present study apparent molar volume ϕV, and viscosity B-coefficient B, have been determined for l-ascorbic acid (Vit.C), nicotinic acid (Vit.B3), thiamine hydrochloride (HCl salt of Vit. B1) and pyridoxine hydrochloride (HCl salt of Vit. B6) in aqueous magnesium chloride solutions (mB = 0.1 to 0.5 mol∙kg−1) over the temperature range (288.15–318.15) K at pressure (101.3) kPa. The partial molar volume of transfer, ∆trϕVo, and viscosity B-coefficient of transfer, ∆trB, for these compounds from water to aqueous solutions of magnesium chloride have been determined from the corresponding data. First (∂ϕVo/ ∂T) P and second (∂2ϕVo/ ∂T2)P, derivative of ϕVo and dB/dT, values have been calculated. B/ϕVo ratio, activation free energy of viscous flow of vitamins ∆μ2o#, and other parameters have also been calculated. Both volumetric and viscometric studies suggest the presence of complex interactions at lower concentrations, but the role of cosolute becomes decisive at higher concentrations. The dB/dT values and activation parameters (∆S2o#, ∆H2o#) values suggest that l-ascorbic acid, thiamine hydrochloride and pyridoxine hydrochloride show bond making tendencies with magnesium chloride while nicotinic acid shows comparatively less affinity with magnesium chloride.