Development of several sensors for Ca/sup ++/ potentiometric measurement in blood

An original protocol for the multicenter coordinated evaluation of seven analyzers for the measurement of ionized calcium is reported. The comparison of the instruments was made possible by using specific biological samples and newly developed HEPES or MOPS buffered aqueous reference solutions. The results for the evaluation of Ca/sup 2+/ instruments have shown that: (1) good precision and linearity are obtained for most of the analyzers with the aqueous buffered solutions; (2) serum is the most suitable medium; the values obtained on whole blood are more scattered and therefore whole blood specimens should be restricted for urgent circumstances; and (3) sampling and storage conditions of the specimens do not restrain routine determinations in clinical laboratories. This evaluation shows the good quality of small automatic instruments which allows rapid and reliable ionized calcium measurements.<>