A simple assay method for added stable caesium in blood plasma

Abstract

Summary A new assay method was developed to determine added stable caesium (Cs) in blood plasma. The simple and inexpensive method is based on the competition between stable and radioactive Cs in binding to ammonium-iron(II)-hexacyanoferrate(III) (AFCF), followed by the precipitation of AFCF-bound Cs with plasma proteins, and the measurement of the radioactivity of the precipitate. For data treatment, standard procedures of radioimmunoassay were used. At present stage, the qualitative detection limit is around 0.2 μmol L-1, and the practical limit for quantitative results around 1 μmol L-1. The method is applicable only for recently added Cs in blood plasma, and cannot be used to measure endogenous plasma Cs or Cs in other tissues. Determining plasma kinetics of Cs might be useful in the study of some aspects of potassium kinetics, since these two alkali metals are transported into cells by the same cellular mechanism (Na,K-ATPase).