A method for the determination of sodium, potassium, magnesium and lithium concentrations in erythrocytes

A technique for the rapid and accurate estimation of intra-erythrocyte concentrations of Na, K, Li and Mg is described. CoEDTA is used as a marker to estimate plasma trapped in the red cell column ; the use of this compound constitutes a novel departure from other marker substances previously used. Plasma trapping was found to average close to 3% (v/v) of the packed cell column. RBC electrolyte values obtained from healthy control subjects were shown to be in good agreement with values reported in the literature.