Buffer standards for the physiological pH of the zwitterionic compound, TAPS, from 5°C to 55°C

The values of the second dissociation constant, pK(2), and related thermodynamic quantities of N-[tris( hydroxymethyl) methyl-3-amino] propanesulfonic acid ( TAPS) have already been reported at 12 temperatures over the temperature range 5 - 55 degrees C, including 37 degrees C. This paper reports the results for the pH of five equimolal buffer solutions with compositions: ( a) TAPS ( 0.03 mol . kg(-1))+ NaTAPS (0.03 mol . kg(-1)); ( b) TAPS (0.04 mol . kg(-1))+ NaTAPS ( 0.04 mol . kg(-1)); ( c) TAPS (0.05 mol . kg(-1))+ NaTAPS (0.05 mol . kg(-1)); ( d) TAPS (0.06 mol . kg(-1))+ NaTAPS (0.06 mol . kg(-1)); and ( d) TAPS (0.08 mol . kg(-1))+ NaTAPS (0.08 mol . kg(-1)). The remaining eight buffer solutions consist of saline media of the ionic strength I = 0.16 mol . kg(-1), matching closely to that of the physiological sample. The compositions are: ( f) TAPS (0.04 mol-kg(-1))+ NaTAPS (0.02 mol-kg(-1)) + NaCl (0.14 mol . kg(-1)); ( g) TAPS (0.05 mol . kg(-1))+ NaTAPS (0.04 mol . kg(-1))+ NaCl (0.12 mol . kg(-1)); ( h) TAPS (0.6 mol . kg(-1))+ NaTAPS (0.04 mol . kg(-1))+ NaCl (0.12 mol . kg(-1)); ( i) TAPS (0.08 mol . kg(-1))+ NaTAPS (0.06 mol . kg(-1))+ NaCl (0.10 mol . kg(-1)); ( j) TAPS (0.04 mol . kg(-1))+ NaTAPS (0.04 mol . kg(-1))+ NaCl (0.12 mol . kg(-1)); (k) TAPS ( 0.05 mol . kg(-1))+ NaTAPS (0.05 mol . kg(-1))+ NaCl (0.11 mol . kg(-1)); ( l) TAPS (0.06 mol . kg(-1))+ NaTAPS (0.06 mol . kg(-1))+ NaCl (0.10 mol . kg(-1)); and ( m) TAPS (0.08 mol . kg(-1)) + NaTAPS (0.08 mol . kg(-1)) + NaCl (0.08 mol . kg(-1)). These buffers are recommended as a pH standard for clinical measurements in the range of physiological application. Conventional pH values, designated as pH(s), for all 13 buffer solutions from 5 to 55 degrees C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 degrees C for buffer solutions, designated above as ( b), ( c), ( d), ( e), ( j), ( l), and ( m); have been determined based on the difference in the values of the liquid junction potentials between the accepted phosphate standard and the buffer solutions under investigation.