Multielectrolyte concentration equilibria in the presence of ion-exchange resins. A model for the control of blood electrolyte levels

Abstract

The study reported here was undertaken in the course of examining the possibility of using ion exchangers to control blood electrolyte levels in a form of haemodialysis.

A description and justification is given of the transfer-function method of predicting multielectrolyte equilibria in the presence of an ion-exchange resin. The initial solution concentrations are written as components of a vector S and the transfer function is the matrix which, multiplied by the vector, produces a vector F of which the components are the final concentrations, either on the resin or in the supernatant solution, depending on the matrix used. The transfer function can be linear or of higher order. The method is used to calculate ternary equilibria on resins and ternary and quaternary equilibria in solutions. Solutions used to compare the calculations with experimental observations contained the chloride salts of the commonest cations found in blood at concentrations ranging from values found in normal blood to values beyond the most extreme medically observed conditions of electrolyte imbalance. The superiority of the transfer-function method over a graphical method for calculating the equilibria is demonstrated with regard to accuracy and simplicity of calculation. Consideration is given to controlling the electrolyte concentrations in multielectrolyte solutions by determining the electrolyte loading of an ion-exchange resin such that desired concentration changes would be brought about in the solution when a particular quantity of the resin was added to it.