Buffer Capacity in Heterogeneous Multicomponent Systems. Review

Abstract

Abstract. The quantitative basis of the theory of buffer properties for two-phase acid-base buffer systems and for multicomponent heterogeneous systems has been derived. The analytical equations for buffer action with respect to all components for diverse multicomponent systems were deduced. It was found a remarkable relation of proportionality between β i quantities. It is shown, that the buffer properties in relation to the solid phase components are amplifi ed with an increase of solubility due to protolytic or complex formation equilibria in saturated solutions. It has been established, that the buffer capacities of components are mutually proportional, whereas for heterogeneous systems these relationships depend on the stoichiometric composition of solid phases. The deduced equations can be applied to the assessment of buffer action of the systems "Natural mineral -soil solution", containing soluble and insoluble chemical species. A number of the important conclusions concerning the investigated buffer systems has been made. The obtained results can be used in various areas of chemical and biochemical researches, especially in soil science, ecological sciences, analytical chemistry, pharmacology, pharmaceutics, medical industry and synthetic organic chemistry Keywords: buffer action, complex formation, thermodynamic stability, extraction multicomponent system, heterogeneous equilibria. IntroductionBuffer capacity is an important concept in many areas of science: analytical and electroanalytical chemistry [7], etc. The capacity of buffer systems to oppose (resist) to the variation of their composition (usually to рН changes) by infl uence of external fl uxes of chemical compounds of natural or anthropogenic character, that shift chemical equilibria, is called buffer property, and its effi ciency -buffer action. Despite of an abundance of the information on buffer systems, the quantitative theory of buffer action has been developed only for mono-phase systems [8,9]. The buffer action of mono-phase buffers is usually based on protolytic equilibria between water, a weak acid or base or ampholytic compound and their conjugate pairs [10,11]. The widespread use of buffers as well as the variety of chemical processes and phenomena associated with a certain acidity of solutions explains the constant interest in designing and studying new buffer systems.Unlike the classical mono-phase buffer systems in which the buffer components are dissolved in a unique phase, in two-phase (heterogeneous) buffers they are distributed between two phases: in aqueous phase and solid (gaseous or liquid) phase. The aqueous (buffer) phase contains all the charged particles and a restricted quantity of electro-neutral species. The solid phase contains in signifi cant quantities only electro-neutral particles and serves as their reservoir by means of which the equilibrium is adjusted and one of parameters of buffer system is maintained constantly [9][10][11][12][13][14][15][16][17][18]. The buffer action of two-phase systems is based on ...