title: A comparison of reference method values for sodium, potassium and chloride with method-dependent assigned values.
abstract: The concentrations of sodium, potassium, and chloride in various control sera were determined by reference methods. The reference method values were compared with the corresponding method-dependent assigned values. Sodium: Measurements by flame photometry and ion selective electrodes differed on the whole by less than 1% from the reference method value; determinations by photometry differed, however, by -4.7%. Potassium: The mean bias was -1.2% with flame photometry and -0.4% with ion selective electrodes, whereas nephelometric procedures differed by -1.9 or -4.8%. Chloride: Satisfactory agreement was obtained with values given for ion selective electrodes (-0.3%), for some coulometric procedures (-0.7 and 0.4%), and photometric determinations using mercury rhodanide (-0.5 and +0.7%). Values for mercurimetric titration and for photometric determinations using mercury 2,4,6-tri-(2-pyridyl)-s-triazine differed by + 2.5 and + 1.8%. Proposals concerning the allowable deviation from reference method values are discussed.
mesh_terms: D002712:Chlorides / Q000097:blood*; D004566:Electrodes; D006801:Humans; D007202:Indicators and Reagents; D008722:Methods; D010783:Photometry / Q000379:methods; D011188:Potassium / Q000097:blood*; D011786:Quality Control; D012016:Reference Values; D012964:Sodium / Q000097:blood*; D013053:Spectrophotometry / Q000379:methods
chemical_list: D002712:Chlorides; D007202:Indicators and Reagents; D012964:Sodium; D011188:Potassium