Calculation of the pH and the titratable acidity in clinically used infusion solutions

• Published in: Computer methods and programs in biomedicine Vol. 87; no. 2; pp. 160 - 169
• Main Authors: Lang, Werner, Meier, Nils
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01-08-2007
• Subjects: Acid–base equilibria; Apparent p K; Biomimetic Materials - chemistry; Body Fluids - chemistry; Clinical infusion solutions; Computer Simulation; Electroneutrality; Fluid Therapy; Hydrogen-Ion Concentration; Infusions, Intravenous; Infusions, Parenteral; Internal Medicine; Mass balance; Models, Chemical; Other; Titrimetry - methods; Mass balance; Apparent p K; Electroneutrality; Acid–base equilibria; Clinical infusion solutions
• ISSN: 0169-2607; 1872-7565
• DOI: 10.1016/j.cmpb.2007.05.003

Abstract Clinically used infusion solutions are complex aqueous mixtures composed of a variety of different salts, acids, and non-electrolytes, and are characterized by composition, initial pH, and titratable acidity (TA). By rigorous treatment as a multi-composed acid–base system, pH and TA were calculated from proton dissociation equilibria, mass balance equations and electroneutrality condition. Nine were arbitrarily chosen as model solutions in which pH and TA were experimentally determined. From composition, and based on a set of apparent acidity constants (p K values) at 37 °C and total ionic strength 0.155 mol/l, pH was calculated by iteration. In the model solutions, measured pH was in the range 5–7, and the difference between calculated and experimental values was ± 0.064. Good agreement was also found between calculated and measured TA: in the range 0–55 mmol/l the mean difference was ± 2.07 mmol/l, if calculated from measured pH, and ±0.95 mmol/l, if calculated from calculated pH.