Calculadora de Buffer

Usa la ecuación Henderson-Hasselbalch para calcular pH de buffer o las cantidades necesarias de ácido/base conjugada. Incluye recetas de buffers comunes (PBS, Tris, HEPES, Citrato) y cálculos de capacidad buffer.

Buffer System

Target pH

Effective range: 6.8 - 8.2

Buffer Concentration

Total Volume

HEPES Buffer, pH 7.4

Component	Conc. (mM)	Mass (g)	1M Stock (mL)
HEPES	29.27	6.976	29.27
HEPES sodium salt	20.73	5.395	20.73

pKa:7.55

[A⁻]/[HA] Ratio:0.708

Total Volume:1000 mL

Dissolve the acid and base forms in ~80% of the final volume of deionized water. Adjust pH with HCl or NaOH if needed. Bring to final volume with deionized water. Autoclave or filter-sterilize as required.

Henderson-Hasselbalch Formula

pH = pKa + log([A⁻]/[HA])

[A⁻]/[HA] = 10^(pH - pKa)

[HA] = C_total / (1 + ratio)

[A⁻] = C_total - [HA]

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What is a Buffer Recipe Calculator?

A buffer recipe calculator determines the exact amounts of acid and conjugate base needed to prepare a buffer solution at a specific pH. It uses the Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]), where pKa is the acid dissociation constant, [A⁻] is the conjugate base concentration, and [HA] is the weak acid concentration. Buffers resist pH changes and are essential in biological experiments, cell culture, enzyme assays, electrophoresis, and chromatography. This tool supports 10 common buffer systems covering pH 3.0 to 11.1, including biological buffers (HEPES, MOPS, Tris, MES) and chemical buffers (Acetate, Citrate, Phosphate).

How to Use This Calculator

Select a buffer system that covers your target pH (each shows pKa and effective range)
Enter your target pH value
Set the desired buffer concentration (mM) and total volume (mL)
Review the recipe: mass (g) of acid and base forms, or volume (mL) of 1M stock solutions
Follow the preparation instructions to dissolve, adjust pH, and bring to final volume

Frequently Asked Questions

How do I choose the right buffer system for my experiment?

Choose a buffer with a pKa within 1.0 pH unit of your target pH. This is the effective buffering range where the buffer resists pH changes most effectively. For biological work at pH 7.4, HEPES (pKa 7.55) or Phosphate (pKa 7.2) are common choices. For Tris-based buffers, note that pKa (8.06) decreases ~0.03 per degree Celsius.

What is the Henderson-Hasselbalch equation?

The Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])) relates the pH of a buffer to the pKa of the weak acid and the ratio of conjugate base to weak acid concentrations. When pH = pKa, the ratio is 1:1 and the buffer has maximum capacity. The equation is accurate within the buffer's effective range (pKa ± 1).

Why is my buffer outside the effective range?

A buffer works best when the target pH is within 1.0 pH unit of its pKa. Outside this range, the ratio of acid to base becomes extreme (>10:1 or <1:10), and the solution loses its ability to resist pH changes. If your target pH is outside the range, choose a different buffer system with a closer pKa value.

How do I prepare the buffer solution after calculating the recipe?

Dissolve the calculated amounts of acid and base forms in approximately 80% of the final volume of deionized water. Use a calibrated pH meter to check and fine-tune the pH with small additions of HCl or NaOH. Then bring the solution to the final target volume. Autoclave (121°C, 15 min) or filter-sterilize (0.22 µm) depending on the buffer's heat stability.