⚗️ Lab Calculators
Buffer Preparation Calculator
Calculate exact volumes and masses to prepare common laboratory buffers at any pH and molarity using the Henderson–Hasselbalch equation.
How to Use the Buffer Preparation Calculator
Select your buffer system from the dropdown, enter the desired pH within the valid range, set the total buffer molarity and final volume, then click Calculate Buffer. The calculator uses the Henderson–Hasselbalch equation to determine the ratio of acid to conjugate base, then calculates exact masses or volumes of each component.
Henderson–Hasselbalch Equation
pH = pKa + log([A⁻] / [HA])
Ratio = [A⁻] / [HA] = 10^(pH − pKa)
pH = desired buffer pH | pKa = acid dissociation constant of buffer | [A⁻] = conjugate base concentration | [HA] = weak acid concentration
Common Buffer Systems and Their pKa Values
Acetate Buffer — pKa 4.76
Range: pH 3.6–5.6. Components: Acetic acid + Sodium acetate. Used for enzyme assays, electrophoresis, and protein crystallisation.
Phosphate Buffer — pKa 7.20
Range: pH 5.8–8.0. Components: NaH₂PO₄ + Na₂HPO₄. Most widely used buffer in biochemistry. PBS is a phosphate-buffered saline.
Tris-HCl — pKa 8.06
Range: pH 7.0–9.0. Components: Tris base + HCl. Standard buffer for DNA/RNA work, agarose gels (TAE, TBE) and protein extraction.
HEPES — pKa 7.55
Range: pH 6.8–8.2. Non-toxic, minimal metal binding. Ideal for cell culture media, microscopy and live-cell imaging experiments.
About Laboratory Buffers
A buffer solution resists changes in pH when small amounts of acid or base are added. Buffers are essential in all areas of biotechnology — maintaining enzyme activity, preserving protein structure, controlling electrophoresis conditions and supporting cell viability in culture.
The effective buffering range of any buffer system is approximately pH = pKa ± 1. Outside this range, buffering capacity drops significantly. Always select a buffer with a pKa close to your desired working pH for maximum stability.
Tips for Buffer Preparation
💧 Always adjust pH after mixing
Weigh components and dissolve in ~80% of final volume. Adjust pH with HCl or NaOH, then make up to final volume. Never adjust volume before pH.
🌡️ pH is temperature-dependent
Tris buffers in particular change pH significantly with temperature — adjust at the temperature you will use the buffer (e.g. 37°C for cell work).
🧂 Add salts separately
NaCl, KCl and other salts in PBS do not affect pH but are added for ionic strength. Weigh them separately and add before final volume adjustment.
🔬 Verify with pH meter
Always confirm final pH with a calibrated pH meter. Calculated ratios give a starting point — small adjustments are normal and expected.
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