title: Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection.
abstract: We report here on the development of a chronopotentiometric readout for ion-selective electrodes that allows one to record transition times in continuous flow conditions without the necessity to stop the flow. A sample plug of 150 μL is injected into the carrier solution (0.5 mM NaCl) and subsequently transported to the detection cell (∼20 μL) at moderate flow rates (∼0.5 mL min(-1)), where a short current pulse (5s) is applied between the ionophore-based working electrode and a biocompatible and nonpolarizable Donnan exclusion anion-exchanger membrane reference/counter electrode. Flow conditions bear an influence on the thickness of the aqueous diffusion layer and result in a shift of the chronopotentiometric transition time with respect to stopped flow. Two models based on rotating disk electrodes and flow chronopotentiometry at metal-based electrodes were used to corroborate the data. The method was successfully applied to the determination of calcium, chloride, alkalinity, acidity, and protamine with a range of ion-selective membranes. Because of the limiting exposure time of ca. 20 s of the membranes with the sample, this approach is demonstrated to be useful for the detection of protamine in the therapeutic range of undiluted human blood.
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
authors.forename: Majid
authors.initials: M
authors.lastname: Ghahraman Afshar
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
authors.forename: Gastón A
authors.initials: GA
authors.lastname: Crespo
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Bakker
mesh_terms: D002118:Calcium / Q000032:analysis*; D002712:Chlorides / Q000032:analysis*; D055664:Electrochemical Techniques; D004566:Electrodes; D006493:Heparin / Q000097:blood; D006801:Humans; D006878:Hydroxides / Q000032:analysis*; D011108:Polymers / Q000032:analysis*; D011479:Protamines / Q000032:analysis* / Q000097:blood; D011522:Protons
chemical_list: D002712:Chlorides; D006878:Hydroxides; D011108:Polymers; D011479:Protamines; D011522:Protons; D006493:Heparin; D002118:Calcium