Transferability of results obtained for sodium, potassium and chloride ions with different analysers

In this study we have assessed transferability in seven different analysers commonly used in clinical chemistry laboratories to measure sodium, potassium and chloride ions. The inaccuracy and linearity of the techniques were satisfactory in most cases, and therefore all the equipment may be used in both pathological and normal ranges of the electrolytes evaluated. In most cases it was possible to correct the inaccuracy. The equipment which gave the best performance when analysing the three ions assessed after considering the Process Capability Index (CPI) and Performance Index (PI) was Nova-5. According to Hyltoft-Petersen's criteria, the results obtained for the three ions with the different analysers cannot be used indiscriminately, apart from potassium. However, after comparison of the results obtained by indirect potentiometry with those obtained by other techniques, we can conclude that the transferability of results is possible in almost every case, as standard deviation from regression (S-y,S-x) was lower than the permissible analytical error. (C) 1998 Elsevier Science B.V. All rights reserved.