TY - JOUR
T1 - Density measurements of potassium phosphate buffer from 4 to 45°C
AU - Schiel, John E.
AU - Hage, David S.
N1 - Funding Information:
This work was supported by the National Institutes of Health under grant RO1 GM44931. J.E. Schiel was supported by the University of Nebraska UCARE program. The authors thank C. Ohnmacht and R. Albro for their advice and help during this project.
PY - 2005/1/30
Y1 - 2005/1/30
N2 - Potassium phosphate buffer is often used in methods such as equilibrium dialysis, high performance liquid chromatography (HPLC), and affinity capillary electrophoresis (ACE) for characterizing the binding of drugs and hormones with proteins or other ligands within the body. In these experiments, the buffer density is often approximated to be that of water and the concentrations of all reagents are assumed to be constant with temperature. However, some difference in density between phosphate buffer and water would be expected, and variations in this density could lead to significant changes in the concentrations of dissolved solutes with temperature. This, in turn, could affect the binding observed for a solute-ligand system in such a buffer. In this study, the densities of potassium phosphate buffers with concentrations up to 0.10 M were measured at or near physiological pH for temperatures ranging from 4-45°C. The general change in density versus temperature followed a quadratic equation, while the changes in density with concentration and pH followed a linear response. The results were used to formulate a general equation that could be used to calculate the density of potassium phosphate buffer at any pH, temperature, and concentration within the tested range. This equation and more specialized relationships developed in the temperature, concentration, and pH studies were found to give much greater accuracy in describing the density of these buffers versus a previous relationship developed for solutions containing only potassium dihydrogen phosphate.
AB - Potassium phosphate buffer is often used in methods such as equilibrium dialysis, high performance liquid chromatography (HPLC), and affinity capillary electrophoresis (ACE) for characterizing the binding of drugs and hormones with proteins or other ligands within the body. In these experiments, the buffer density is often approximated to be that of water and the concentrations of all reagents are assumed to be constant with temperature. However, some difference in density between phosphate buffer and water would be expected, and variations in this density could lead to significant changes in the concentrations of dissolved solutes with temperature. This, in turn, could affect the binding observed for a solute-ligand system in such a buffer. In this study, the densities of potassium phosphate buffers with concentrations up to 0.10 M were measured at or near physiological pH for temperatures ranging from 4-45°C. The general change in density versus temperature followed a quadratic equation, while the changes in density with concentration and pH followed a linear response. The results were used to formulate a general equation that could be used to calculate the density of potassium phosphate buffer at any pH, temperature, and concentration within the tested range. This equation and more specialized relationships developed in the temperature, concentration, and pH studies were found to give much greater accuracy in describing the density of these buffers versus a previous relationship developed for solutions containing only potassium dihydrogen phosphate.
KW - Affinity capillary electrophoresis
KW - Binding studies
KW - Density
KW - High performance liquid chromatography
KW - Phosphate buffer
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U2 - 10.1016/j.talanta.2004.06.029
DO - 10.1016/j.talanta.2004.06.029
M3 - Article
C2 - 18969825
AN - SCOPUS:8444237396
SN - 0039-9140
VL - 65
SP - 495
EP - 500
JO - Talanta
JF - Talanta
IS - 2 SPEC. ISS.
ER -