MEASUREMENTS OF SODIUM AND POTASSIUM IN NEWBORNS AND PREMATURES BY ION-SELECTIVE ELECTRODES AND FLAME PHOTOMETRY - INFLUENCE OF LIPID AND PROTEIN-CONTENT OF BLOOD

The alternative use of flame photometry and ion selective electrodes f or electrolyte determinations in neonatology led to the question how t he two methods agree. 104 routine blood samples were taken as matched pairs for a comparison of sodium and potassium determinations. Pre-ana lytical error was avoided by the mode of blood collection. The influen ce of the protein and lipid content of blood on the differences betwee n the methods was determined by calculating its water content and maki ng a post-correction of the flame values. Thus the differences for sod ium could be reduced, whereas the differences for potassium slightly i ncreased. As long as the imprecision of sodium determination is a mean ingful methodological problem, the influence of the protein and lipid content of neonatal blood is not the main factor for differences betwe en ISE and flame photometry.