Centrifugal ion-selective electrode system for potassium in whole blood

We describe a novel ion-selective electrode (ISE) system that can be used in the Abbott Vision analyzer. A reusable sensor pack and a disposable test pack have been miniaturized to approximately the size and weight of a conventional Vision test pack, thus eliminating the need for a separate ISE module. The sensor pack contains a fluid path, battery-powered electronics, and screw-in electrodes. The test pack contains separate chambers and fluid channels for a blood specimen and two aqueous calibrators. During a run, plasma is separated from blood cells and is moved sequentially, along with the two calibrators, into and out of the sensor pack by centrifugal force. Each run includes checks for electromechanical integrity, fluid contamination, calibration slope and intercept, and specimen hemolysis. The system operates with CVs of less than 2% and gives results that correlate well with those by flame photometry and direct ISE methods. Either skin-puncture or venipuncture whole blood can be assayed, as well as serum or plasma.