Multicomponent two-phase buffer systems

Two-phase buffer systems containing two or more acid—base pairs and having a considerable buffer capacity over a wide pH range are described. When acid—base pairs of the same type are combined, the rule of additivity of buffer capacity is valid, but when the two-phase buffers contain an organic acid and an organic base, the rule of additivity does not apply if ion-pair extraction occurs to a significant extent. Equations for calculation of buffer capacity curves in the latter case are reported. The differentiating effect of the organic solvent allows multicomponent two-phase buffers to be prepared from acids whose strength in water is practically equal.