Efforts will be undertaken to employ ion-selective membrane electrodes for clinical analysis of enzymes, electrolytes, and other body fluid constituents. Methods will be developed for the determination of clinically important substances in serum, whole blood, and urine involving the employment of crystal membrane, enzyme coated and other electrodes in continuous analysis systems with capabilities of handling 100-200 samples per hour. It is expected that the proposed approach will result in desirable simplifications of the chemistries involved, by elimination of dialysis and color development steps, and will produce a significant reduction in analysis costs, by the elimination of expensive optical and electronic instrumentation as well as a reduction in the quantities and number of required reagents. A second part of the proposed research is directed toward the development and evaluation of ion-selective micro electrodes for cations and anions using crystal probes with tip sizes below 5 microns in diameter. It is expected that these micro probes will be useful in sub-microliter samples, as continuous sensors in fluid streams, and as direct probes for measurements in restricted body passages.