pH in physiological salt solutions: direct measurements

Abstract

Calculations of pH in modified Krebs solutions by inserting PCO2 and total-CO2 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 PCO2 is complicated as the concentration of bicarbonate, the dissociation constant and the solubility of CO2 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 O2-CO2 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.

The Potential Role for Impaired Mucosal Integrity in the Generation of Esophageal Pain Using Capsaicin in Humans: An Explorative Study

“…The saline infused in our study had a pH value of 6.2, whereas the solution in the study by Farré had a pH value of 7.2 ( 5 ). The pH value of physiological saline can vary between 6.15 and 8.15 ( 33 ). In this sense, our control condition rather resembles the effect of a weak acid than that of a neutral solution and may therefore have resulted in the observed decrease of mucosal impedance.…”

Pyrrolidinyl caffeamide against ischemia/reperfusion injury in cardiomyocytes through AMPK/AKT pathways

“…In the normoxia condition, 2.2 g/L NaHCO 3 was added to the medium to adjust PH to 7.4. In the hypoxia condition, sodium lactate (8 μM) was added to the medium to induce stress, and the PH value of the medium was adjusted to 6.8 by adding 0.57 g/L NaHCO 3 , according to the Henderson-Hasselbalch equation: PH = 6.1 + log [52 × (mg/ml NaHCO 3 /%CO 2 ) -1] [ 25 ]. PLCA (0.1, 0.3, 1, and 3 μM) and metformin (30 μM) were added to the medium before hypoxia was initiated.…”