| Abstract
| - Poly(styrene-co-divinylbenzene)-based monolithic capillaries of an inner diameter of 200 μm and a length of 2−5mm have been used to construct Ca2+-, Ag+-, and Na+-selective electrodes. The membranes consist of a solutionof ionophore and ion exchanger in bis(2-ethylhexyl) sebacate or 2-nitrophenyl octyl ether, which are used asplasticizers in conventional PVC-based membranes. Withcapillaries of low porosity, the potentiometric responsesdown to 10-8−10-9 M solutions do not depend on thecomposition of the internal solution, which indicates astrong suppression of transmembrane ion fluxes. Thus,no tedious optimization of the inner solution is requiredwith monolith ISEs. The lower detection limits of Ag+- andCa2+-ISEs are comparable to the best ones obtainedearlier with optimized inner solutions. Additionally, amonolithic Na+-selective ISE has been obtained exhibitinga lower detection limit of 3 × 10-8 M Na+. With monolithiccapillaries of higher porosity and fused-silica GC capillaries, the transmembrane flux effects are noticeable butstill significantly smaller than with conventional PVCmembranes.
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