This research direction places ion-selective membranes under instrumental control by using a range of electrochmical excitation methods to perform work and impose well defined ion fluxes across the sample–membrane interface. Often the actual signal is acquired during an open circuit potential period to avoid contributions from the ohmic drop. These approaches allow one to perform chronopotentiometric measurements and hence to obtain complementary speciation information, to increase the sensitivity, operate selective membranes as ion pumps and achieve all-solid-state reference electrodes. This research was originally inspired by our earlier work on understanding spontaneous transmembrane ion fluxes and their role in dictating the detection limit of ion-selective electrodes.
Publications:
(1) Gao, W. Y.; Zdrachek, E.; Xie, X. J.; Bakker, E. A Solid-State Reference Electrode Based on a Self-Referencing Pulstrode. Angew Chem Int Edit 2020, 59 (6), 2294-2298. DOI: 10.1002/anie.201912651.(2) Gao, W. Y.; Xie, X. J.; Bakker, E. Direct Potentiometric Sensing of Anion Concentration (Not Activity). ACS Sensors 2020, 5 (2), 313-318. DOI: 10.1021/acssensors.9b02523.
(3) Zdrachek, E.; Bakker, E. From Molecular and Emulsified Ion Sensors to Membrane Electrodes: Molecular and Mechanistic Sensor Design. Accounts Chem Res 2019, 52 (5), 1400-1408. DOI: 10.1021/acs.accounts.9b00056.
(4) Gao, W. Y.; Jeanneret, S.; Yuan, D. J.; Cherubini, T.; Wang, L.; Xie, X. J.; Bakker, E. Electrogenerated Chemiluminescence for Chronopotentiometric Sensors. Anal Chem 2019, 91 (7), 4889-4895. DOI: 10.1021/acs.analchem.9b00787.
(5) Jansod, S.; Afshar, M. G.; Crespo, G. A.; Bakker, E. Alkalinization of Thin Layer Samples with a Selective Proton Sink Membrane Electrode for Detecting Carbonate by Carbonate-Selective Electrodes. Anal Chem 2016, 88 (7), 3444-3448. DOI: 10.1021/acs.analchem.6b00346.
(6) Jansod, S.; Afshar, M. G.; Crespo, G. A.; Bakker, E. Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes. Biosens Bioelectron 2016, 79, 114-120. DOI: 10.1016/j.bios.2015.12.011.
(7) Afshar, M. G.; Crespo, G. A.; Bakker, E. Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection. Anal Chem 2016, 88 (7), 3945-3952. DOI: 10.1021/acs.analchem.6b00141.
(8) Jeanneret, S.; Crespo, G. A.; Afshar, M. G.; Bakker, E. GalvaPot, a custom-made combination galvanostat/potentiostat and high impedance potentiometer for decentralized measurements of ionophore-based electrodes. Sensor Actuat B-Chem 2015, 207, 631-639. DOI: 10.1016/j.snb.2014.10.084.
(9) Afshar, M. G.; Crespo, G. A.; Bakker, E. Coulometric Calcium Pump for Thin Layer Sample Titrations. Anal Chem 2015, 87 (19), 10125-10130. DOI: 10.1021/acs.analchem.5b02856.
(10) Jarolimova, Z.; Crespo, G. A.; Xie, X. J.; Afshar, M. G.; Pawlak, M.; Bakker, E. Chronopotentiometric Carbonate Detection with All-Solid-State lonophore-Based Electrodes. Anal Chem 2014, 86 (13), 6307-6314. DOI: 10.1021/ac5004163.
(11) Crespo, G. A.; Afshar, M. G.; Bakker, E. Chronopotentiometry of pure electrolytes with anion-exchange donnan exclusion membranes. J Electroanal Chem 2014, 731, 100-106. DOI: 10.1016/j.jelechem.2014.08.007.
(12) Afshar, M. G.; Crespo, G. A.; Xie, X. J.; Bakker, E. Direct Alkalinity Detection with Ion-Selective Chronopotentiometry. Anal Chem 2014, 86 (13), 6461-6470. DOI: 10.1021/ac500968c.
(13) Xie, X. J.; Crespo, G. A.; Bakker, E. Oxazinoindolines as Fluorescent H+ Turn-On Chromoionophores For Optical and Electrochemical Ion Sensors. Anal Chem 2013, 85 (15), 7434-7440. DOI: 10.1021/ac401367b.
(14) Ozdemir, M. S.; Marczak, M.; Bohets, H.; Bonroy, K.; Roymans, D.; Stuyver, L.; Vanhoutte, K.; Pawlak, M.; Bakker, E. A Label-Free Potentiometric Sensor Principle for the Detection of Antibody-Antigen Interactions. Anal Chem 2013, 85 (9), 4770-4776. DOI: 10.1021/ac400514u.
(15) Crespo, G. A.; Bakker, E. Dynamic electrochemistry with ionophore based ion-selective membranes. Rsc Adv 2013, 3 (48), 25461-25474. DOI: 10.1039/c3ra43751e.
(16) Crespo, G. A.; Afshar, M. G.; Bakker, E. Direct Detection of Acidity, Alkalinity, and pH with Membrane Electrodes. Anal Chem 2012, 84 (23), 10165-10169. DOI: 10.1021/ac302868u.
(17) Afshar, M. G.; Crespo, G. A.; Bakker, E. Direct Ion Speciation Analysis with Ion-Selective Membranes Operated in a Sequential Potentiometric/Time Resolved Chronopotentiometric Sensing Mode. Anal Chem 2012, 84 (20), 8813-8821. DOI: 10.1021/ac302092m.
(18) Gemene, K. L.; Bakker, E. Flash chronopotentiometric sensing of the polyions protamine and heparin at ion-selective membranes. Anal Biochem 2009, 386 (2), 276-281. DOI: 10.1016/j.ab.2008.12.023.
(19) Gemene, K. L.; Bakker, E. Measurement of total calcium by flash chronopotentiometry at polymer membrane ion-selective electrodes. Anal Chim Acta 2009, 648 (2), 240-245. DOI: 10.1016/j.aca.2009.07.004.
(20) Xu, Y.; Shvarev, A.; Makarychev-Mikhailov, S.; Bakker, E. Reversible detection of proteases and their inhibitors by a pulsed chronopotentiometric polyion-sensitive electrode. Anal Biochem 2008, 374 (2), 366-370. DOI: 10.1016/j.ab.2007.10.043.
(21) Xu, Y.; Ngeontae, W.; Pretsch, E.; Bakker, E. Backside calibration chronopotentiometry: Using current to perform ion measurements by zeroing the transmembrane ion flux. Anal Chem 2008, 80 (19), 7516-7523. DOI: 10.1021/ac800774e.
(22) Gemene, K. L.; Bakker, E. Direct sensing of total acidity by chronopotentiometric flash titrations at polymer membrane ion-selective electrodes. Anal Chem 2008, 80 (10), 3743-3750. DOI: 10.1021/ac701983x.
(23) Bhakthavatsalam, V.; Bakker, E. Operational limits of controlled current coulometry with ion-selective polymeric membranes. Electroanal 2008, 20 (3), 225-232. DOI: 10.1002/elan.200703979.
(24) Bakker, E.; Bhakthavatsalam, V.; Gemene, K. L. Beyond potentiometry: Robust electrochemical ion sensor concepts in view of remote chemical sensing. Talanta 2008, 75 (3), 629-635. DOI: 10.1016/j.talanta.2007.10.021.
(25) Xu, Y.; Xu, C.; Shvarev, A.; Becker, T.; De Marco, R.; Bakker, E. Kinetic modulation of pulsed chronopotentiometric polymeric membrane ion sensors by polyelectrolyte multilayers. Anal Chem 2007, 79 (18), 7154-7160. DOI: 10.1021/ac071201p.
(26) Gemene, K. L.; Shvarev, A.; Bakker, E. Selectivity enhancement of anion-responsive electrodes by pulsed chronopotentiometry. Anal Chim Acta 2007, 583 (1), 190-196. DOI: 10.1016/j.aca.2006.09.042.
(27) Makarychev-Mikhailov, S.; Shvarev, A.; Bakker, E. Calcium pulstrodes with 10-fold enhanced sensitivity for measurements in the physiological concentration range. Anal Chem 2006, 78 (8), 2744-2751. DOI: 10.1021/ac052211y.
(28) Bhakthavatsalam, V.; Shvarev, A.; Bakker, E. Selective coulometric release of ions from ion selective polymeric membranes for calibration-free titrations. Analyst 2006, 131 (8), 895-900. DOI: 10.1039/b602906j.
(29) Xu, Y. D.; De Marco, R.; Shvarev, A.; Bakker, E. Reversible electrochemical monitoring of surface confined reactions at liquid-liquid interfaces by modulation of ion transfer fluxes. Chem Commun 2005, (24), 3074-3076. DOI: 10.1039/b503548a.
(30) Shvarev, A.; Bakker, E. Response characteristics of a reversible electrochemical sensor for the polyion protamine. Anal Chem 2005, 77 (16), 5221-5228. DOI: 10.1021/ac050101l.
(31) Shvarev, A.; Bakker, E. Distinguishing free and total calcium with a single pulsed galvanostatic ion-selective electrode. Talanta 2004, 63 (1), 195-200. DOI: 10.1016/j.talanta.2003.10.010.
(32) Makarychev-Mikhailov, S.; Shvarev, A.; Bakker, E. Pulstrodes: Triple pulse control of potentiometric sensors. J Am Chem Soc 2004, 126 (34), 10548-10549. DOI: 10.1021/ja047728q.
(33) Shvarev, A.; Bakker, E. Pulsed galvanostatic control of ionophore-based polymeric ion sensors. Anal Chem 2003, 75 (17), 4541-4550. DOI: 10.1021/ac034409t.
(34) Shvarev, A.; Bakker, E. Reversible electrochemical detection of nonelectroactive polyions. J Am Chem Soc 2003, 125 (37), 11192-11193. DOI: 10.1021/ja037167n.
(35) Jadhav, S.; Bakker, E. Selectivity behavior and multianalyte detection capability of voltammetric ionophore-based plasticised polymeric membrane sensors. Anal Chem 2001, 73 (1), 80-90. DOI: 10.1021/ac000569i.
(36) Jadhav, S.; Meir, A. J.; Bakker, E. Normal pulse voltammetry as improved quantitative detection mode for amperometric solvent polymeric membrane ion sensors. Electroanal 2000, 12 (16), 1251-1257. DOI: Doi 10.1002/1521-4109(200011)12:16<1251::Aid-Elan1251>3.3.Co;2-G.
(37) Jadhav, S.; Bakker, E. Voltammetric and amperometric transduction for solvent polymeric membrane ion sensors. Anal Chem 1999, 71 (17), 3657-3664. DOI: DOI 10.1021/ac990195x.