Modeling Acid-Base by Minimizing Charge-Balance.

Area of Science:

• Biochemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Accurate pH determination is crucial in biological and chemical systems.
• Modeling complex solutions with multiple buffers and non-ideal conditions presents significant challenges.
• Existing methods may not adequately account for interactions and varying ionic strengths.

Purpose of the Study:

• To develop a robust method for calculating equilibrium pH in any fluid with multiple buffers.
• To account for non-ideal conditions, including activity coefficients and ionic strength.
• To provide a practical computational tool for pH modeling.

Main Methods:

• Utilized root finding on the charge balance equation to determine equilibrium pH.
• Incorporated Davies' equation for single-ion activity coefficients to model non-ideal states.
• Developed an iterative algorithm to update apparent dissociation constants and identify equilibrium.
• Created the "ABCharge" R package for comprehensive pH and related parameter calculations.

Main Results:

• Demonstrated a monotonic relationship between proton concentration and buffer charge.
• Showcased guaranteed conservation of thermodynamic dissociation constants and total buffer concentrations.
• Validated the algorithm against theoretical results and clinical pH measurements.
• The "ABCharge" package provides detailed outputs including pH, activity coefficients, and ionic strength.

Conclusions:

• The developed algorithm accurately calculates equilibrium pH for complex, non-ideal solutions.
• The "ABCharge" R package offers a practical and versatile tool for researchers.
• The method is adaptable to future advancements in single-ion activity coefficient assessments.