Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection

详细信息    查看全文

• 作者：Majid Ghahraman Afshar ; Gastón A. Crespo ; Eric Bakker
• 刊名：Analytical Chemistry
• 出版年：2016
• 出版时间：April 5, 2016
• 年：2016
• 卷：88
• 期：7
• 页码：3945-3952
• 全文大小：505K
• ISSN：1520-6882

文摘

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.