Automated enzymatic determination of sodium in serum.

An automated method based on the principles of flow-injection analysis is proposed for the enzymatic determination of sodium ion in serum. The method relies on the activation of beta-galactosidase by the analyte. The features of the proposed method include linear range between 1 and 1700 mumol/L, a sampling rate of 50 samples/h, a sample volume of 50 microL, and the absence of interferences from species usually present in serum. The results obtained were consistent with those provided by widely used methods such as those based on flame spectrometry and direct potentiometry with ion-selective electrodes.