pH / Buffer / pKa Calculator
Standard pharmaceutical calculation, laboratory analysis and research tools.
Calculate pH, buffer relationships and pKa-related quantities using standard pharmaceutical chemistry equations for acid-base and buffer calculations.
What Is pH?
pH is a logarithmic measure related to hydrogen ion activity and is used to describe the acidity or alkalinity of an aqueous system.
Henderson–Hasselbalch Equation
For a weak acid buffer, the Henderson–Hasselbalch relationship is commonly written as pH = pKa + log([A−]/[HA]), where [A−] represents the conjugate base and [HA] represents the weak acid.
What Is pKa?
pKa is related to the acid dissociation constant and indicates the tendency of a weak acid to dissociate.
Buffer Calculations
Buffer calculations can be used to determine pH, pKa or the ratio of conjugate base to weak acid. The concentrations or amounts used must be interpreted consistently with the selected equation.
Pharmaceutical Applications
pH and buffer calculations are important in formulation development, stability studies, pharmaceutical solutions, biological systems and evaluation of drug ionisation.
Frequently Asked Questions
What is the Henderson–Hasselbalch equation?
It is a relationship commonly used to calculate the pH of a weak-acid buffer from its pKa and conjugate-base to acid ratio.
What does pKa indicate?
pKa is related to the acid dissociation constant and describes the ionisation tendency of a weak acid.
Why are buffers important in pharmacy?
Buffers help maintain an appropriate pH in pharmaceutical formulations and laboratory systems.