Examining and Calculating the pH of 2-[N-Morpholino]ethanesulfonic Acid (MES) Buffer Solution from 5°C to 55°C

In biomedical, biological, and clinical laboratories, knowledge of the pH of blood and physiological fluids is of great importance. This paper reports the results for the pH of three buffer solutions free of chloride ions. The remaining six buffer solutions have saline media of ionic strength I = 0.16 mol . kg-1 , matching closely to that of the physiological sample. Conventional paH values for the three buffer solutions without the chloride ion and six buffer solutions with the chloride ion at I = 0.16 mol . kg-1 from 5°C to 55°C have been calculated. The operational pH values for five buffer solutions at 5°C and 55°C have been determined based on the difference in the values of the liquid junction potentials between the blood phosphate standard and the experimental buffer solutions. Five of these buffers are recommended as standards for the physiological pH range of 7.5 to 8.5. It was concluded that all emf data are stable, reliable, and accurate. The MES buffer solutions are considered standards of assigned pH and will be useful when buffer solutions of known conventional pH are required.