A comparison of the measurement of sodium and potassium by flame photometry and ion-selective electrode.

Although sodium and potassium have been the most commonly assayed analytes by clinical chemists for many years there have been fewer analytical principles used routinely than for most other analytes. The introduction of the direct-reading ion-selective electrode has led to a re-examination of the basic concepts of the methods involved, and this in turn to a reassessment of the interpretation of the measurement of sodium in certain clinical situations. As a result there is a case for all clinical chemistry laboratories having access to a direct-reading ion-selective electrode for sodium estimation.