Phosphate Buffer Solution Calculator

The Phosphate Buffer Solution Calculator estimates the exact mass of phosphate salts needed to prepare a buffer solution using inputs like pH, concentration, and volume. This tool helps biochemists and students achieve precise pH control for reliable experimental results. Whether you are setting up cell cultures, conducting biochemical assays, or performing electrophoresis, this calculator provides the accurate measurements required for success.

Target pH of your buffer solution (1-14)
Total concentration of the buffer in molarity (M)
Total volume of buffer solution to prepare
Temperature of the solution (affects pKa value)
Choose the appropriate phosphate buffer system for your pH range
Adjustment for ionic strength effects on pKa (typically -0.1 to 0.1)

How Mass of Phosphate Salts Is Calculated

Mass of phosphate salts represents the specific weight of the acid and base components required to stabilize your solution at the desired pH. The calculation uses the Henderson-Hasselbalch equation to find the correct ratio of ions.

pH = pKa + log10([base]/[acid])

Where:

  • pH = Desired pH of the solution
  • pKa = Acid dissociation constant of the buffer system
  • [base] = Concentration of the base component
  • [acid] = Concentration of the acid component

First, the tool adjusts the pKa value based on your temperature and ionic strength inputs to ensure precision. Next, it calculates the total moles of buffer needed from your concentration and volume targets. Finally, it splits these moles into acid and base portions and converts them to grams using standard molar masses. This method ensures your mixture will chemically resist pH changes effectively.

What Your Mass of Phosphate Salts Means

The resulting values tell you exactly how much of each powdered salt to weigh out and dissolve in water for your experiment.

Common Use Cases

  • Biological Assays: For cell culture or enzyme studies, use a lower concentration (0.01 M to 0.1 M) to mimic natural salt levels in the body.
  • Electrophoresis: Use higher concentrations (0.05 M to 0.2 M) to ensure proper electrical conductivity when separating DNA or proteins.
  • General Lab Work: A 0.1 M concentration at pH 7.4 is standard for washing steps and solution preparation.

Important

Always verify the final pH with a calibrated meter after mixing, as slight temperature variations or impurities can shift the value.

Disclaimer: This calculator provides theoretical values for informational purposes only and is not a substitute for professional laboratory training. Always consult your lab's standard operating procedures and safety data sheets when preparing chemical solutions.

After preparing your buffer, store it at 4°C and check the pH again before using it in critical experiments to ensure stability.