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pH in physiological salt solutions: direct measurements
Author(s) -
Abrahamsen J.,
Norrie B.,
Andersen P. K.,
Stokke D. B.,
Nedergaard O. A.
Publication year - 1990
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1990.tb03157.x
Subject(s) - bicarbonate , dissociation constant , solubility , dissociation (chemistry) , analytical chemistry (journal) , thermodynamics , carbon dioxide , constant (computer programming) , aqueous solution , acid dissociation constant , inorganic chemistry , chemistry , chromatography , biochemistry , organic chemistry , physics , receptor , computer science , programming language
Calculations of pH in modified Krebs solutions by inserting Pco 2 and total‐CO 2 in the Henderson‐Hasselbalch (H.‐H.) equation are obvious as the equation originally served for this purpose. An exact calculation of the relation between pH and Pco 2 is complicated as the concentration of bicarbonate, the dissociation constant and the solubility of CO 2 change. Furthermore, the dissociation constant in the H.‐H. equation is constant only if activities are used in the equation instead of stoichiometric concentrations. We therefore investigated the influence of different carbon dioxide tensions and bicarbonate concentrations on directly measured pH of organ baths aerated with mass‐spectrometric analyzed O 2 ‐CO 2 gases. For reference precision buffers were used. The measured pH values differed distinctly from calculated pH values in the acidic and alkaline parts of the pH interval investigated (6.57–8.15). Measurements of actual pH with proper calibration standards therefore seem mandatory.