Abstract
This paper reports the results for the pH of three buffer solutions free of chloride ion. The remaining six buffer solutions have saline media of the 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 7.5 to 8.5.
Highlights
The buffer substances recommended by Good et al [1,2,3] have proven very useful for the measurement of the pH of blood and the control of pH in a region close to that of physiological solution
The disadvantages are as follows: 1) phosphates act as inhibitors to enzymatic processes; 2) phosphate precipitates occur with some polyvalent cations, such as Mg2+ and Ca2+, present in the blood; and 3) the temperature coefficient of the phosphate buffer is –0.0028 pH unit/K as compared to that of whole blood (–0.015 pH unit/K) and plasma (0.01 pH unit/K) [5]
Conventional paH values have been evaluated by the method of Bates et al [11,14,15,16] for three buffer solutions without NaCl and six buffer solutions in the presence of NaCl
Summary
The buffer substances recommended by Good et al [1,2,3] have proven very useful for the measurement of the pH of blood and the control of pH in a region close to that of physiological solution. We have reported the pK2 values of 2-[N-morpholino] ethanesulfonic acid (MES) [1] at temperatures from 5 ̊C to 55 ̊C, including 37 ̊C. This zwitterionic buffer system has been recommended by Good and coworkers [2,3] for use as a physiological buffer. The disadvantages are as follows: 1) phosphates act as inhibitors to enzymatic processes; 2) phosphate precipitates occur with some polyvalent cations, such as Mg2+ and Ca2+, present in the blood; and 3) the temperature coefficient of the phosphate buffer is –0.0028 pH unit/K as compared to that of whole blood (–0.015 pH unit/K) and plasma (0.01 pH unit/K) [5]
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