Standard buffer of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (Bes) for use in the physiological pH range 6.6 to 7.4

Second-stage dissociation constants of piperazine-N,N'-bis(2-ethanesulfonic acid) monosodium monohydrate and related thermodynamic functions in water from 5 to 55.degree.C

“…Purified hydrogen gas was swept through each solution to remove dissolved air before the cells were filled. The design of the cells (12), the method of the preparation of the hydrogen electrodes (13), and the silver-silver bromide electrodes (14,15) have been previously reported. The constant-temperature bath was controlled to within 0.02 °C.…”

“…A null detector (Leeds and Northrup Model 9829) with a sensitivity of 25 µ was employed. The detailed procedure for the preparation of solutions and other experimental details are presented elsewhere (5). The cells displayed excellent stability and the initial, middle, and final emf readings at 25 °C agreed to within 0.05 mV on the average.…”

“…These compounds are all ampholytes (with zwitterionic structures) and are useful buffers compatible with most media of physiological interest for the pH range from 6 to 8. In earlier studies of biochemical buffers, the pK values and related thermodynamic quantities of N-substituted glycine [that is, IV-tris(hydroxymethyl)methylglycine (Tricine) (3, 4)] and N-substituted taurine [that is, Ar,7V-bis(2-hydroxymethyl)-2-aminoethanesulfonic acid (BES) (5,6)] have been determined. Other substances along this line that have been studied, mostly by Bates and his co-workers (7, 8), include 7V,N-bis(2-hydroxymethyl)glycine (Bicine) (7), tris(hydroxymethyl)aminoethane (TRIS) (8,9), and very recently four N-substituted aminoethanesulfonic acids (10).…”

Thermodynamic Study of the Second‐Stage Dissociation of N, N‐Bis‐(2‐Hydroxyethyl)Glycine (Bicine) in Water at Different Ionic Strength and Different Solvent Mixtures

“…Considerable attention has been given to the effect of changes of temperature on the dissociation constants of dipolar ionic compounds [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . These studies have provided precise knowledge about the thermodynamic quantities associated with the dissociation process as well as about the suitability of a biological buffer.…”

Buffers for the physiological pH range: thermodynamic constants of four substituted aminoethanesulfonic acids from 5 to 50.degree.C

“…The substituted aminoethanesulfonic acids HEPES, TES, and BES have K2 values between 10-7 and 10-8 and are therefore of particular use in the preparation of buffer solutions for control of acidity in the pH region of physiological interest. Buffer solutions prepared from BES and strong alkali have been suggested as secondary standards for pH (16). Furthermore, in work as yet unpublished, we have shown that buffers composed of HEPES or TES in NaCl solutions matching the ionic strength of blood serum are useful standards for pH measurements in the clinical laboratory.…”