Buffertsystem

A buffer system (Buffertsystem) is a chemical or biological mechanism that resists changes in pH when small amounts of acid or base are added. It usually consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. The buffer neutralizes added H+ by converting it to the weak acid, and neutralizes added OH- by converting it to water and the conjugate base, thereby limiting pH change. In chemistry, buffer effectiveness is greatest when the pH is near the pKa of the buffering pair, and the buffer capacity depends on the concentrations of the components.

Common chemical buffers include acetic acid/acetate, phosphate (H2PO4-/HPO4^2-), and bicarbonate/carbonic acid buffers. The bicarbonate system is especially important in physiological fluids such as blood and extracellular fluid, where it helps maintain pH around 7.35 to 7.45.

Biological and medical contexts rely on buffers to stabilize conditions in experiments and in living organisms. In the laboratory, buffers are used in titrations, enzymatic assays, and chromatography to maintain stable pH. In medicine, intravenous fluids and formulations often include buffers to prevent pH shifts that could harm tissues or enzymes.

Limitations of buffer systems include finite buffering capacity, especially at extreme pH values; once the capacity is exceeded, pH changes can be rapid. Buffer performance is temperature-dependent and can shift with changes in ionic strength.