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Angewandte Chemie (International Ed. in... 2007For most chemists, potentiometry with ion-selective electrodes (ISEs) primarily means pH measurements with a glass electrode. Those interested in clinical analysis might... (Review)
Review
For most chemists, potentiometry with ion-selective electrodes (ISEs) primarily means pH measurements with a glass electrode. Those interested in clinical analysis might know that ISEs, routinely used for the determination of blood electrolytes, have a market size comparable to that of glass electrodes. It is even less well known that potentiometry went through a silent revolution during the past decade. The lower detection limit and the discrimination of interfering ions (the selectivity coefficients) have been improved in many cases by factors up to 10(6) and 10(10), respectively, thus allowing their application in fields such as environmental trace analysis and potentiometric biosensing. The determination of complex formation constants for lipophilic hosts and ionic guests is also covered in this Minireview.
Topics: Calibration; Hydrogen-Ion Concentration; Immunoassay; Ion-Selective Electrodes; Potentiometry; Sensitivity and Specificity
PubMed: 17457791
DOI: 10.1002/anie.200605068 -
Critical Reviews in Analytical Chemistry 2019The complexity of biological objects and the rapid change in their composition after sampling, the variety of compounds of different chemical nature, possessing... (Review)
Review
The complexity of biological objects and the rapid change in their composition after sampling, the variety of compounds of different chemical nature, possessing oxidative and antioxidant properties, make the task of its estimating extremely nontrivial and important for food, nutrients and human health characterization. The paper discusses the use of potentiometry in determining integral antioxidant/oxidant activity mainly of biological fluids and human skin. The source of information is the electrode potential shift that occurs when the analyzed object is inserted in the solution of the mediator system or when the mediator system is exposed to human skin. The experimental approaches, protocols, calculations are described. A number of examples of antioxidant activity and oxidative stress estimation in medicine are presented. The works show lower levels of antioxidant activity (AOA) of plasma and blood serum in patients with cardiovascular diseases, obesity, and malignant neoplasms as compared with the healthy volunteers. It was found out that antioxidant activity of fertile men semen is higher than AOA of infertile patients. Using the method discussed have shown that in some infertile male patients antioxidant activity of semen has been accompanied by oxidant activity. It has been found, that antioxidant activity of skin increases after intake of ascorbic acid and vitamin-enriched juices. The described approach holds considerable promise for monitoring oxidative stress of the whole organism and its systems, and for selecting effective and safe therapy. Thus, it opens up new opportunities in expanding the use of analytical chemistry in such an important field as medicine.
Topics: Antioxidants; Disease; Humans; Medicine; Oxidative Stress; Potentiometry
PubMed: 30285479
DOI: 10.1080/10408347.2018.1496009 -
Medical Progress Through Technology 1988Ion-selective potentiometry is used more and more in clinical medicine for the determination of electrolytes in various body fluids. With regard to K+, Na+, Ca2+ and Cl-... (Review)
Review
Ion-selective potentiometry is used more and more in clinical medicine for the determination of electrolytes in various body fluids. With regard to K+, Na+, Ca2+ and Cl- this technique has almost completely displaced flame photometry, atomic absorption spectrophotometry and coulometry. Moreover, reliable automated devices have facilitated routine analyses. Until now there are 6 different types of ion-selective sensors: glass membrane, solid phase, fluid membrane, carrier, gas-sensitive, and enzyme electrodes with immobilized enzymes. The latter are particularly used for in vivo monitoring, especially for continuous blood glucose monitoring. The essential fields of application in the clinical laboratory are the determinations of the cations H+, K+, Na+, Ca2+, Mg2+ and NH3+, and the anions F-, I-, Br-, Cl- and HCO3-. Despite the wide-spread application of ion-selective potentiometry a number of disturbing factors have to be taken into account by the user as well as by the manufacturer in order to get satisfactory results. For instance, there are differences between direct and indirect potentiometry. Moreover, the activities measured cannot be extrapolated readily to the desired concentrations. A careful and accurate calibration, a suitable sample preparation and an adjustment of the measuring conditions to the characteristics of the specimen and the matrix of the sample is necessary before each measurement. Therefore, a consequent internal and external quality control is necessary to achieve an optimal quality of these methods determining vital parameters in medicine. Thus, the technique of ion-selective potentiometry represents an important milestone in clinical chemistry. Moreover, being a very rapid procedure it is indispensable to clinical diagnostics.
Topics: Body Fluids; Electrodes; Electrolytes; Enzymes; Humans; Potentiometry
PubMed: 3285159
DOI: No ID Found -
Analytica Chimica Acta Jan 2013Ion-selective potentiometry enjoys practical utility as a simple analytical technique to measure ionic constituents in complex samples. Advances in the field have... (Review)
Review
A tutorial on the application of ion-selective electrode potentiometry: an analytical method with unique qualities, unexplored opportunities and potential pitfalls; tutorial.
Ion-selective potentiometry enjoys practical utility as a simple analytical technique to measure ionic constituents in complex samples. Advances in the field have improved the selectivity and decreased the detection limit of ion-selective electrodes (ISEs) by orders of magnitude such that trace analysis in micro and nanomolar concentrations is now possible with potentiometric sensors. This tutorial reviews the fundamental principles of ion-selective potentiometry, describes the practical considerations involved in the use of these sensors to measure real samples, and discusses the statistical evaluation of experimental results compared with alternative analytical techniques.
Topics: Electric Conductivity; Electrodes; Potentiometry
PubMed: 23327940
DOI: 10.1016/j.aca.2012.11.022 -
Analytical Chemistry May 2023Potentiometry based on the galvanic cell mechanism, i.e., galvanic redox potentiometry (GRP), has recently emerged as a new tool for in vivo neurochemical sensing with...
Potentiometry based on the galvanic cell mechanism, i.e., galvanic redox potentiometry (GRP), has recently emerged as a new tool for in vivo neurochemical sensing with high neuronal compatibility and good sensing property. However, the stability of open circuit voltage () outputting remains to be further improved for in vivo sensing application. In this study, we find that the stability could be enhanced by adjusting the sort and the concentration ratio of the redox couple in the counterpart pole (i.e., indicating electrode) of GRP. With dopamine (DA) as the sensing target, we construct a spontaneously powered single-electrode-based GRP sensor (GRP) and investigate the correlation between the stability and the redox couple used in the counterpart pole. Theoretical consideration suggests that the drift is minimum when the concentration ratio of the oxidized form (O) to the reduced form (R) of the redox species in the backfilled solution is 1:1. The experimental results demonstrate that, compared with other redox species (i.e., dissolved O at 3 M KCl, potassium ferricyanide (KFe(CN)), and hexaammineruthenium(III) chloride (Ru(NH)Cl)) used as the counterpart pole, potassium hexachloroiridate(IV) (KIrCl) exhibits better chemical stability and outputs more stable . As a result, when IrCl with the concentration ratio of 1:1 is used as the counterpart, GRP displays not only an excellent stability (i.e., 3.8 mV drifting during 2200 s for in vivo recording) but also small electrode-to-electrode variation (i.e., the maximum variation between four electrodes is 2.7 mV). Upon integration with the electrophysiology, GRP records a robust DA release, accompanied by a burst of neural firing, during the optical stimulation. This study paves a new avenue to stable neurochemical sensing in vivo.
Topics: Potentiometry; Electrodes; Oxidation-Reduction; Dopamine; Iridium
PubMed: 37201512
DOI: 10.1021/acs.analchem.3c00110 -
Analytical Chemistry Sep 2013Measuring the oxidation-reduction potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in...
Measuring the oxidation-reduction potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the solution. Sluggish electron transfer (ET) kinetics with the species will not reflect the "true" Eh of the solution. Here, we present a novel approach by which adsorbed metal nanoparticles (NPs) are used for enhancing ET exchange rates between redox species and electrode surface and therefore affect significantly the measurement of the open circuit potential (OCP) and cyclic voltammetry (CV). The OCP and CV of various organic and inorganic species such as l-dopa, dopac, iron(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. We study the effect of the surface coverage of the stainless steel surface by NPs on the electrochemical response. Moreover, the stainless steel electrode was modified simultaneously by Au and Pt nanoparticles. This improved concurrently the stainless steel response (CV and potentiometry) toward two different species; l-dopa, which shows fast electron transfer on Pt, and catechol, which exhibits fast electron transfer on Au. We believe that this approach could be a first step toward developing a superior electrode for measuring the "true" Eh of complex aquatic systems.
Topics: 3,4-Dihydroxyphenylacetic Acid; Gold; Metal Nanoparticles; Oxidation-Reduction; Platinum; Potentiometry
PubMed: 23947748
DOI: 10.1021/ac401744w -
Critical Reviews in Analytical Chemistry 2021Potentiometry is one of the most important electrochemical methods and potentiometric based sensors have been extensively studied by researchers for many years. The fact... (Review)
Review
Potentiometry is one of the most important electrochemical methods and potentiometric based sensors have been extensively studied by researchers for many years. The fact that potentiometric sensors have several advantages over other analytical devices is another reason for intensive research on the topic. In this area, hundreds of different sensors have been developed till today and introduced into the literature. The successful use of the developed sensors, particularly in real sample analysis, has made potentiometric sensors the center of attention. In this review, we highlight the studies which have been successfully applied to the developed drug samples and also to many real samples, with high recovery rates.
Topics: Animals; Biosensing Techniques; Drug Monitoring; Humans; Ion-Selective Electrodes; Ions; Pharmaceutical Preparations; Potentiometry
PubMed: 31928212
DOI: 10.1080/10408347.2019.1711013 -
Analytical Chemistry Mar 2016In situ potentiometry and null ellipsometry was combined and used as a tool to follow the kinetics of biofouling of ion-selective electrodes (ISEs). The study was...
In situ potentiometry and null ellipsometry was combined and used as a tool to follow the kinetics of biofouling of ion-selective electrodes (ISEs). The study was performed using custom-made solid-contact K(+)-ISEs consisting of a gold surface with immobilized 6-(ferrocenyl)hexanethiol as ion-to-electron transducer that was coated with a potassium-selective plasticized polymer membrane. The electrode potential and the ellipsometric signal (corresponding to the amount of adsorbed protein) were recorded simultaneously during adsorption of bovine serum albumin (BSA) at the surface of the K(+)-ISEs. This in situ method may become useful in developing sensors with minimized biofouling.
Topics: Biofouling; Potentiometry; Serum Albumin, Bovine
PubMed: 26864883
DOI: 10.1021/acs.analchem.5b04364 -
Journal of Chromatography. A Sep 2019Analytical techniques are extensively used in various fields of human activity to define quality and usage safety patterns of goods and consumables. Between those,... (Review)
Review
Analytical techniques are extensively used in various fields of human activity to define quality and usage safety patterns of goods and consumables. Between those, liquid chromatography is probably the most common, generally combined with optical detectors. Alternatively, electroanalytical techniques provide versatile tools that offer high selectivity and sensitivity in a short time, using simple and low cost instrumentation. Amperometric, coulometric and conductimetric detectors are thus well established in HPLC with commercially available instrumentation. Despite sharing some of the stated features, the use of potentiometric detectors seems however overlooked. Potentiometry with ion-selective electrodes has been highlighted in both batch and flow analysis systems, evidenced by numerous applications performed worldwide. The determination of electrolytes in blood samples, heavy metals in natural water samples and pharmaceutical drugs in bulk drug materials are some of the representative examples. The developments achieved so far in hydrodynamic separation systems proved the great potential of potentiometry to become a competitive detection technique with the many others. Therefore, it is intended to present an overview about potentiometric detection in liquid chromatography with the purpose of enhance its importance for future analytical applications.
Topics: Anions; Cations; Chromatography, Liquid; Electrodes; Potentiometry
PubMed: 31227359
DOI: 10.1016/j.chroma.2019.06.006 -
Analytical Chemistry Aug 2022In potentiometric sensing, the preparation of the electrodes preceding a measurement is often the most time-consuming step. Eliminating the conditioning process can...
In potentiometric sensing, the preparation of the electrodes preceding a measurement is often the most time-consuming step. Eliminating the conditioning process can significantly speed up the preparation procedure, but it can also compromise the need for proper pre-equilibration of the membrane. We propose here a symmetric setup to address this challenge with an identical indicator and reference elements measured against each other, thereby compensating for potential drift. This strategy allows one to achieve potentiometric measurements using non-conditioned all-solid-state ion-selective electrodes for the detection of nitrate and potassium ions with Nernstian response slopes and detection ranges identical to those of conventional systems. To establish symmetry, a set of solid-contact ion-selective electrodes placed in a reference cell is measured against a set of identical electrodes in a sample cell. By subtracting the potentials between the two cells, potential instabilities not directly relevant to the measuring sample are eliminated, giving minimal potential drifts and stable 5-day potential responses. The value of the nitrate-selective electrodes in the symmetric setup had a standard deviation of just 3 mV for the 5-day period in contrast to 19 mV in the asymmetric system, clearly demonstrating the influence of the conditioning step which is almost eliminated in the former system. During the 20 h potential monitoring experiments, the drift dropped to below 0.3 mV/min in less than 6 min, as opposed to an average time of 35 min for the asymmetric system. The applicability of the proposed setup was successfully demonstrated with the measurement of nitrate in a river water sample, where a potential drift lower than 0.1 mV/min was reached in less than 5 min of first contact with solution.
Topics: Electrodes; Ion-Selective Electrodes; Nitrates; Potassium; Potentiometry
PubMed: 35968664
DOI: 10.1021/acs.analchem.2c01728