Histidine Buffer Calculator

Overview

The Histidine Buffer Calculator helps determine the amounts of histidine and histidine hydrochloride (HCl) needed to prepare a buffer solution with a specified pH, concentration, and volume. Histidine is commonly used for buffering in the pH range of 5.5 to 7.5, making it suitable for biological applications.

Calculation Principles

The Henderson-Hasselbalch equation is used to calculate the ratio of histidine to histidine HCl needed to achieve the desired pH:

\[ \text{pH} = \text{pKa} + \log\left(\frac{[\text{Histidine}]}{[\text{Histidine HCl}]}\right) \]

Where the pKa of histidine is approximately 6.0.

Example Calculation

To prepare a 0.1 M histidine buffer at pH 6.5 with a total volume of 1 L:

1. Determine the histidine-to-histidine HCl ratio using the Henderson-Hasselbalch equation.
2. Calculate the moles of each component based on the concentration and volume.
3. Convert moles to grams using the molar masses:
   • Histidine: 155.16 g/mol
   • Histidine HCl: 191.63 g/mol

This calculator simplifies the process by automating these calculations, ensuring accurate buffer preparation.