What is a buffer?

• A buffer is a solution that resists significant pH changes when small amounts of acid or base are added. They’re crucial in analytical chemistry, HPLC methods, biological assays, and many QC/R&D applications
• Steps to Prepare a Buffer:
• Select the buffer system
• Choose based on your target pH and the buffer’s pKa (best buffering capacity within ±1 pH unit of pKa).
• Calculate desired molarity
• Decide the concentration that provides adequate buffering without affecting ionic strength excessively.
• Weigh the exact salt
• Use the calculator to get the precise mass based on molecular weight, volume, and concentration.
• Dissolve and adjust pH
• Dissolve the salt in ~70–80% of final volume, then adjust pH with acid/base (e.g., HCl or NaOH).
• Make up to volume
• After pH adjustment, add water to reach the final desired volume.
• Filter (if needed)
• Especially important for HPLC use: filter through 0.45 µm (or 0.22 µm) filters to remove particulates.
• Always check hydration state of salts (e.g., anhydrous vs. trihydrate) – molecular weight differs!
• Use CO₂-free water to avoid pH drift in phosphate or carbonate buffers.
• Label solutions with name, concentration, pH, date, and analyst initials.
• Use freshly prepared buffers for sensitive assays; discard old solutions.
• Store at proper temperature and protect from light if applicable.
• Periodically verify pH, especially for long-term stored buffers.
• Common Buffer Examples
• Sodium phosphate (pKa ≈ 7.2)
• Acetate buffer (pKa ≈ 4.7)
• Tris buffer (pKa ≈ 8.1)
• Citrate buffer (pKa ≈ 3.1, 4.8, 6.4)
• By following these steps and tips — and using this calculator — you can save time, improve accuracy, and standardize buffer prep across your team.