The preparation and response characteristics of a carbonate-selective polymer membrane electrode are reported. The electrode is prepared by incorporating Aliquat 336, trifluoroacetyl-p-butylbenzene and di-2ethylhexyl sebacate or dioctyl phthalate in a poly(vinylchloride) membrane matrix. The effect of membrane composition and electrode response in various buffer systems are examined. Under buffer conditions appropriate for practical measurements, potentiometric data yield the following sclcctivity pattern: CIO; = salicylate > total carbon dioxide species > I-> NO; > acetate > Cl-> Br: The electrode can be readily fabricated in tubular form and utilized within a very simple flow-injection arrangement to determine total carbon dioxide species. The possible applications of the electrode to serum CO, measurements as well as within newly devised gas-sensing arrangements for dissolved CO, are also examined. The accurate and rapid determination of total carbon dioside species (e.g., CO?, hydrogencarbonate, and carbonate) in physiological, industrial, and environmental samples presents a formidable challenge_ At present,

Several new electrochemical devices designed for detecting ammonia and carbon dioxide in physiological samples have in common the elimination of the fragile glass pH internal electrode used in the conventional Severinghaus-design potentiometric gas sensors. In one new approach, the pH glass electrode can be replaced with a neutral carrier-based polymer-membrane pH electrode. Alternatively, to improve response characteristics and selectivity, we have used ion-selective polymer membranes responsive to ammonium and carbonate as internal sensing elements in conjunction with appropriate internal buffer reagents. The use of inner polymer membranes rather than glass membranes enables the fabrication of essentially disposable devices having rapid response times. In addition, we have constructed automated continuous-flow NH3- and CO2-sensing systems involving novel tubular forms of the polymer-membrane electrodes and a simple flow-through gas dialysis arrangement. The polymer electrode-based systems described offer many unique and practical advantages over existing gas-sensing units.