pHbuffring

pH buffering is the ability of a solution to resist changes in pH when small amounts of acid or base are added. This resistance is provided by a buffer system, typically composed of a weak acid and its conjugate base, or a weak base and its conjugate acid. When acid is added, the conjugate base neutralizes part of the acid to form the weak acid; when base is added, the weak acid donates a proton to form the conjugate base. This interplay slows shifts in pH.

Buffer capacity depends on the concentrations of the buffering components; higher concentrations offer greater capacity but can influence other solution properties. The effective buffering range is usually within about one pH unit of the buffer’s pKa. The Henderson-Hasselbalch relationship, pH = pKa + log([A-]/[HA]), describes how the pH relates to the ratio of conjugate base to acid in the buffer.

Common buffers include acetate (pKa ~4.76), phosphate buffers with multiple pKa values (near 2.15, 7.20, and 12.35), and bicarbonate/carbonic acid systems important in blood. In biology, cellular and extracellular fluids rely on buffering to maintain near-constant pH, with blood buffered primarily by bicarbonate and proteins.

Applications span laboratory chemistry, biology, medicine, and environmental science. Buffers are used to maintain stable pH in reactions, culture media, IV solutions, and environmental waters. Limitations include finite buffer capacity and changes due to temperature, ionic strength, or strong acid/base additions, which can overwhelm buffering and cause pH drift. Proper buffer selection depends on the target pH, desired capacity, and experimental conditions.