Monolithic capillary-based ion-selective electrodes.
Poly(styrene-co-divinylbenzene)-based monolithic capillaries of an inner diameter of 200 mum and a length of 2-5 mm have been used to construct Ca2+-, Ag+-, and Na+-selective electrodes. The membranes consist of a solution of ionophore and ion exchanger in bis(2-ethylhexyl) sebacate or 2-nitrophenyl octyl ether, which are used as plasticizers in conventional PVC-based membranes. With capillaries of low porosity, the potentiometric responses down to 10(-8)-10(-9) M solutions do not depend on the composition of the internal solution, which indicates a strong suppression of transmembrane ion fluxes. Thus, no tedious optimization of the inner solution is required with monolith ISEs. The lower detection limits of Ag+- and Ca2+-ISEs are comparable to the best ones obtained earlier with optimized inner solutions. Additionally, a monolithic Na+-selective ISE has been obtained exhibiting a lower detection limit of 3 x 10(-8) M Na+. With monolithic capillaries of higher porosity and fused-silica GC capillaries, the transmembrane flux effects are noticeable but still significantly smaller than with conventional PVC membranes.
Laboratorium für Organische Chemie, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
Tamás
T
Vigassy
Christian G
CG
Huber
Reiner
R
Wintringer
Ernö
E
Pretsch
D002118:Calcium / Q000737:chemistry*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D017736:Ion-Selective Electrodes; D011137:Polystyrenes / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*
D011137:Polystyrenes; C432006:divinylbenzene-polystyrene copolymer; D012834:Silver; D012964:Sodium; D002118:Calcium