Basbuffert

Basbuffert, or base buffer, is a buffer solution that resists changes in pH upon the addition of small amounts of acid or base. It achieves this by containing a weak base and its conjugate acid in solution, typically in the form of a base B and its conjugate acid BH+. When acid is added, B neutralizes some of the added protons to form BH+. When base is added, BH+ can donate a proton to reform B. This opposing chemistry minimizes shifts in pH within a certain range.

The relationship between pH and the composition of a base buffer is described by Henderson–Hasselbalch chemistry for bases: pOH = pKb + log([BH+]/[B]), and pH = 14 − pOH at 25°C. The buffer is most effective near the pKb value of the weak base and within about one pH unit of that value in terms of the ratio of conjugate base to conjugate acid. Temperature and ionic strength influence the exact pH and buffer capacity.

Common basbuffers include solutions of ammonia/ammonium chloride (NH3/NH4+), borate buffers (borate/base pairs with boric acid), and Tris-based systems (Tris base with Tris-HCl). These buffers are widely used in biochemistry and molecular biology to maintain alkaline conditions or near-neutral pH during enzymatic reactions, electrophoresis, and cell culture.

Preparation and practical use involve mixing a weak base with its conjugate acid salt, adjusting with small amounts of acid or base, and controlling ionic strength with a supporting salt. Buffer capacity is greatest near the target pH and decreases away from it.