Stabilized potentiometric solid-state polyion sensors using silver-calixarene complexes as additives within ion-exchanger-based polymeric films

Novel solid-state sensors for biomedically important polyions (i.e., hepari n and protamine) that exhibit significantly enhanced initial EMF stability are prepared by incorporation of lipophilic silver-calixarene complexes alo ng with the required ion-exchangers within polymeric films. A dithioether o f tertiary butyl calix[4]arene together with its silver complex are added t o the polyion sensing membranes which are deposited on a silver-epoxy condu ctor of a solid-state transducer. The silver-complex serves as a reversible electron transfer agent between the organic polymer film and the underlyin g solid-state conductor, resulting in highly reproducible starting EMF valu es and improved initial signal stability. This approach is further employed to devise a heparin sensing cartridge for blood measurements based on a no vel differential measurement mode. One sensor responds to heparin, while th e second identical solid-state sensor serves as a pseudo reference electrod e with all heparin present in the sample within this half-cell complexed by the addition of excess protamine. The cartridges are evaluated by monitori ng heparin response in spiked dog blood using poly(vinyl chloride) (PVC) bl ends and fluorinated silicone rubber (Dow Corning RTV 730) films containing appropriate levels of ion-exchanger and Ag+-calixarene/free calixarene add itives.