Effect of potassium phosphate buffer on volumetric behavior of glycine in aqueous solutions at different temperatures

The apparent molar volume (V∅) of glycine in water and in 100, 500 and 1000 mM aqueous potassium phosphate buffer (KPB) solutions have been obtained from density measurements at different temperatures (288.15 to 328.15 K, including physiological temperature) and at different pH values (1.00, 7.40 and 14.00) by using vibrating-tube digital density meter. The estimated partial molar volumes at infinite dilution (V2o) have been used to obtain the corresponding transfer volume ( ∆trV2o) from water to aqueous potassium phosphate buffer solutions. Interaction parameters have been calculated from ∆trV2o data. The partial molar expansibilities (∂ V2o | ∂ T)P at infinite dilution and (∂2V2o | ∂ T2)P values have also been determined from the V2o data at different temperatures. The hydration numbers (nH) of glycine at pH 7.4 have been determined from the V2o data in the presence of KPB at different temperatures. The results have been discussed in terms of various interactions operating in these systems.