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1.
Sensors (Basel) ; 21(22)2021 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-34833757

RESUMO

Towards clarifying the spatio-temporal neurotransmitter distribution, potentiometric redox sensor arrays with 23.5-µm resolution were fabricated. The sensor array based on a charge-transfer-type potentiometric sensor comprises 128×128 pixels with gold electrodes deposited on the surface of pixels. The sensor output corresponding to the interfacial potential of the electrode changed logarithmically with the mixture ratio of K3Fe(CN)6 and K4Fe(CN)6, where the redox sensitivity reached 49.9 mV/dec. By employing hydrogen peroxidase as an enzyme and ferrocene as an electron mediator, the sensing characteristics for hydrogen peroxide (H2O2) were investigated. The analyses of the sensing characteristics revealed that the sensitivity was about 44.7 mV/dec., comparable to the redox sensitivity, while the limit of detection (LOD) was achieved to be 1 µM. Furthermore, the oxidation state of the electron mediator can be the key to further lowering the LOD. Then, by immobilizing oxidizing enzyme for H2O2 and glutamate oxidase, glutamate (Glu) measurements were conducted. As a result, similar sensitivity and LOD to those of H2O2 were obtained. Finally, the real-time distribution of 1 µM Glu was visualized, demonstrating the feasibility of our device as a high-resolution bioimaging technique.


Assuntos
Técnicas Biossensoriais , Peróxido de Hidrogênio , Eletrodos , Ácido Glutâmico , Ouro , Oxirredução , Potenciometria
2.
Anal Chem ; 93(46): 15543-15549, 2021 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-34767713

RESUMO

Iodide (I-) is an essential micronutrient for thyroid function. Hence, rapid and portable sensing is important for I- quantification in food and biological samples. Herein, we report the first example of a halogen bonding (XB) tripodal ionophore (XB1) which is selective for the I- anion. NMR binding studies of XB1 and its H-triazole analog HB2 with I- demonstrated the dominant influence of XB interactions between the ionophore and the I- analyte. The phase boundary model was applied to formulate iodide-selective electrodes with the ionophore XB1. The optimal electrode exhibited a near-Nernstian response of -51.9 mV per decade within a large dynamic range (10-1 to 10-6 M) and notably anti-Hofmeister selectivity for I- over thiocyanate (SCN-), enabling the in situ determination of I- in complex samples. This work establishes XB as a viable supramolecular interaction in the potentiometric sensing of anions.


Assuntos
Halogênios , Iodetos , Eletrodos , Ionóforos , Potenciometria
3.
Sensors (Basel) ; 21(21)2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34770587

RESUMO

Potentiometric pH measurements have long been used for the bioanalysis of biofluids, tissues, and cells. A glass pH electrode and ion-sensitive field-effect transistor (ISFET) can measure the time course of pH changes in a microenvironment as a result of physiological and biological activities. However, the signal interpretation of passive pH sensing is difficult because many biological activities influence the spatiotemporal distribution of pH in the microenvironment. Moreover, time course measurement suffers from stability because of gradual drifts in signaling. To address these issues, an active method of pH sensing was developed for the analysis of the cell barrier in vitro. The microenvironmental pH is temporarily perturbed by introducing a low concentration of weak acid (NH4+) or base (CH3COO-) to cells cultured on the gate insulator of ISFET using a superfusion system. Considering the pH perturbation originates from the semi-permeability of lipid bilayer plasma membranes, induced proton dynamics are used for analyzing the biomembrane barriers against ions and hydrated species following interaction with exogenous reagents. The unique feature of the method is the sensitivity to the formation of transmembrane pores as small as a proton (H+), enabling the analysis of cell-nanomaterial interactions at the molecular level. The new modality of cell analysis using ISFET is expected to be applied to nanomedicine, drug screening, and tissue engineering.


Assuntos
Técnicas Biossensoriais , Transistores Eletrônicos , Eletrodos , Concentração de Íons de Hidrogênio , Íons , Potenciometria
4.
Anal Chem ; 93(44): 14737-14742, 2021 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-34699175

RESUMO

Classical application of ion-selective membranes is limited to either electrochemical or optical experiments. Herein, the proposed ion-selective membrane system can be used in both modes; each of them offering competitive analytical parameters: high selectivity and linear dependence of the signal on logarithm of analyte concentration, high potential stability in potentiometric mode, or applicability for alkaline solutions in optical mode. Incorporation of analyte ions into the membrane results in potentiometric signals, as in a classical system. However, due to the presence of lipophilic positively charged ions, polymer backbones, full saturation of the membrane is prevented even for long contact time with solution. The presence of both positively charged and neutral forms of conducting polymers in the membrane results in high stability of potential readings in time. Optical signal generation is based on polythiophene particulates dispersed within the ion-selective membrane as the optical transducer. An increase of emission is observed with an increase of analyte contents in the sample.


Assuntos
Membranas Artificiais , Íons , Membranas , Potenciometria
5.
Analyst ; 146(23): 7109-7117, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34591042

RESUMO

We have designed and synthesized a multifunctional dendritic molecular probe that selectively detects Cu2+ ions via potentiometric and fluorometric techniques with low detection limits (3.5 µM in potentiometry, 15 nM in fluorometry). The selective and reversible binding of the molecule with the Cu2+ ion was used to make a solid-state microsensor (diameter of 25 µm) by incorporating the molecular probe into the carbon-based membrane as an ionophore for Cu(II). The Cu(II) microelectrode has a broad linear range of 10 µM to 1 mM with a near Nernstian slope of 30 mV/log [aCu2+] and detection limit of 3.5 µM. The Cu(II) microsensor has a fast response time (1.5 s), and it has a broad working pH range from 3.5 to 6.0. The incorporation of the hydrophobic dendritic moiety makes the ionophore less prone to leaching in an aqueous matrix for potentiometric measurement. The cinnamaldehyde component of the molecule helps detection of Cu2+ ions fluorometrically, as indicated by a change in fluorescence upon selective and reversible binding of the molecular probe to the Cu2+ ions. The strategic design of the molecular probe allows us to detect Cu2+ ions in drinking water by using this novel dendritic fluoroionophore and solid-state Cu2+ - ion-selective microelectrode.


Assuntos
Água Potável , Sondas Moleculares , Fluorometria , Íons , Potenciometria
6.
Anal Chem ; 93(37): 12655-12663, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34476942

RESUMO

Metal wires have been used as an alternative to liquid junctions for the connection of solutions in microfabricated electrochemical devices. They exhibit similar performance to liquid junctions, provided that the interfacial potentials at both ends of the wires were appropriately canceled. Cyclic voltammograms of devices with liquid junctions and metal wires were very similar when no current or a low current flowed through the metal wire between the working and reference electrodes. Iridium wires with iridium oxide at both ends facilitated canceling of the interfacial potentials at either end of the junction particularly well, and were used effectively for voltammetry, amperometry, and potentiometry by adjusting the pH of the solutions in the working and reference electrode compartments to be equal. This approach was used to effectively integrate a reliable common reference electrode between multiple working electrodes and to conduct automated electrochemical control of solution transport in microfluidic systems.


Assuntos
Técnicas Biossensoriais , Eletrodos , Potenciometria
7.
Sensors (Basel) ; 21(17)2021 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-34502770

RESUMO

A supramolecular atropine sensor was developed, using cucurbit[6]uril as the recognition element. The solid-contact electrode is based on a polymeric membrane incorporating cucurbit[6]uril (CB[6]) as an ionophore, 2-nitrophenyl octyl ether as a solvent mediator, and potassium tetrakis (4-chlorophenyl) borate as an additive. In a MES-NaOH buffer at pH 6, the performance of the atropine sensor is characterized by a slope of (58.7 ± 0.6) mV/dec with a practical detection limit of (6.30 ± 1.62) × 10-7 mol/L and a lower limit of the linear range of (1.52 ± 0.64) × 10-6 mol/L. Selectivity coefficients were determined for different ions and excipients. The obtained results were bolstered by the docking and spectroscopic studies which demonstrated the interaction between atropine and CB[6]. The accuracy of the potentiometric analysis of atropine content in certified reference material was evaluated by the t-Student test. The herein proposed sensor answers the need for reliable methods providing better management of this hospital drug shelf-life while reducing its flush and remediation costs.


Assuntos
Atropina , Polímeros , Eletrodos , Humanos , Ionóforos , Potenciometria
8.
Talanta ; 235: 122815, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34517671

RESUMO

Nano structured ion-selective membranes (ISMs) are very attractive materials for a wide range of sensing and ion separation applications. The present review focuses on the design principles of various ISMs; nanostructured and ionophore/ion acceptor doped ISMs, and their use in biomedical engineering. Applications of ISMs in the biomedical field have been well-known for more than half a century in potentiometric analysis of biological fluids and pharmaceutical products. However, the emergence of nanotechnology and sophisticated sensing methods assisted in miniaturising ion-selective electrodes to needle-like sensors that can be designed in the form of implantable or wearable devices (smartwatch, tattoo, sweatband, fabric patch) for health monitoring. This article provides a critical review of recent advances in miniaturization, sensing and construction of new devices over last decade (2011-2021). The designing of tunable ISM with biomimetic artificial ion channels offered intensive opportunities and innovative clinical analysis applications, including precise biosensing, controlled drug delivery and early disease diagnosis. This paper will also address the future perspective on potential applications and challenges in the widespread use of ISM for clinical use. Finally, this review details some recommendations and future directions to improve the accuracy and robustness of ISMs for biomedical applications.


Assuntos
Técnicas Biossensoriais , Nanoestruturas , Eletrodos Íon-Seletivos , Membranas Artificiais , Polímeros , Potenciometria
9.
Anal Chim Acta ; 1179: 338603, 2021 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-34535249

RESUMO

Light-addressable potentiometric sensor (LAPS) has been widely used in biomedical applications since its advent. As a member of the potentiometric sensors, ion-sensitive LAPS (ISLAPS) can be obtained by modifying ion selective sensing membrane on the sensor surface. Compared with the conventional ion-selective electrodes (ISEs) with liquid contact, the all-solid-state ISEs have more advantages such as easy maintenance, more convenient for miniaturization and practical applications. However, the commonly used ion-sensitive membrane (ISM) matrix like PVC has many limitations such as poor adhesion to silicone-based sensor and easy overflow of the plasticizer from the membrane. In this work, LAPS was combined with a variety of ionophore-doped all-solid-state silicone-rubber ISMs for the first time, to establish a program-controlled multiplexed ISLAPS system for physiological ions (Na+, K+, Ca2+ and H+) detection. The silicone-rubber ISMs have better adhesion to silicon-based sensors without containing plasticizers, which can avoid the plasticizer pollution and improve the long-term stability. A layer of poly(3-octylthiophene-2,5-diyl) (P3OT) was pre-modified on the sensor surface to inhibit the formation of an aqueous layer and improve the sensor lifetime. With the aid of a translation stage, the light spot automatically illuminated the detection sites in sequence, and the response of the four ions could be obtained in one measurement within 1 min. The proposed multiplexed ISLAPS has good sensitivity with micromolar limit of detection (LOD), good selectivity and long-term stability (more than 3 months). The results of the real Dulbecco's Modified Eagle Medium (DMEM) sample detection proved that the ISLAPS system can be used for the physiological ions detection, and is promising to realize a multi-parameter microphysiometer.


Assuntos
Borracha , Elastômeros de Silicone , Eletrodos Íon-Seletivos , Íons , Potenciometria
10.
Anal Chim Acta ; 1181: 338924, 2021 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-34556233

RESUMO

Herein, hybrid carbon sensor has been developed with graphite sheets as a matrix, tricresyl phosphate (TCP) as a plasticizer and nanosheets of 2D Cu-MOF (metal-organic framework) as an electroactive material for the ultrasensitive Cu(II) ion detection in various real samples. Where, the present study proves the efficiency of 2D Cu-MOF as a promising sensing material for the development of Cu(II) ion selective carbon sensor. The developed 2D Cu-MOF nanosheets based sensor containing 2D Cu-MOF: TCP: graphite in the ratio of 2.67: 30.54: 66.79 (% wt/wt) displayed unique Nernstian behavior over two linearity ranges of 1.0 × 10-11-1.0 × 10-9 and 1.0 × 10-5-1.0 × 10-1 mol L-1 with slopes of 29.5 ± 0.25 and 29.6 ± 0.13 mV decade-1, respectively. The fabricated carbon sensor achieved a widely pH independency, fast response time and superior thermal stability with highly selective and ultrasensitive performance. Moreover, It has been efficiently applied for the Cu(II) ion potentiometric estimation in human hair, sesames seeds, two different tea infusions and tap water real samples.


Assuntos
Grafite , Estruturas Metalorgânicas , Carbono , Humanos , Potenciometria , Água
11.
J Neural Eng ; 18(5)2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34547734

RESUMO

Objective. Neural interfaces often rely on charge transfer processes between electrodes and the tissue or electrolyte. Electrochemical processes are at the core of electrode function and, therefore, the key to neural interface stability, electrode performance characterization, and utilization of electrodes as chemical sensors. Electrochemical techniques offer a variety of options to investigate the charge transfer and electrocatalytic properties of electrodes.Approach. In this tutorial, we present various experiments to illustrate the power of electrochemical methods, serve as a reference and guideline, and stimulate deeper understanding of the subject.Main results.As a basis for the following experiments, we discuss the platinum cyclic voltammogram and focus on understanding surface processes and roughness determination. We highlight the importance of appropriate instrumentation using potentiostats and how strongly it can influence results. We then discuss a number of potential-controlled and current-controlled methods for electrode characterization, including chronocoulometry, chronoamperometry, (active) potentiometry, and chronopotentiometry. They illustrate charge transfer caused by both electrode surface processes and the presence of redox-active species, such as dissolved oxygen and hydrogen, or hydrogen peroxide. We also discuss the electrode potential with respect to a reference electrode under various conditions and how it affects its electrochemical properties like surface state, catalytic properties and capability to transfer charge.Significance.Electrochemical methods are still underutilized in neural engineering, and valuable information is therefore often not accessed. Many studies on electrode characterization would benefit from a more consistent and target-oriented electrochemical methodology and instrumentation. That ranges from the investigation of new materials and processes, over electrode performance assessment to the development of more long-term stable and biocompatible neural interfaces. Ultimately, standardization, consistency and comparability will play a key role in the translation of microtechnology into biomedical and clinical applications.


Assuntos
Técnicas Eletroquímicas , Platina , Eletrodos , Eletrólitos , Potenciometria
12.
ACS Sens ; 6(10): 3650-3656, 2021 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-34582164

RESUMO

Potentiometric sensors induce a spontaneous voltage that indicates ion activity in real time. We present here an advanced self-powered potentiometric sensor with memory. Specifically, the approach allows for one to record a deviation from the analyte's original concentration or determine whether the analyte concentration has surpassed a threshold in a predefined time interval. The sensor achieves this by harvesting energy in a capacitor and preserving it with the help of a diode. While the analyte concentration is allowed to return to an original value following a perturbation over time, this may not influence the sensor readout. To achieve the diode function, the sensor utilizes an additional pair of driving electrodes to move the potentiometric signal to a sufficiently high base voltage that is required for operating the diode placed in series with the capacitor and between the sensing probes. A single voltage measurement across the capacitor at the end of a chosen time interval is sufficient to reveal any altered ion activity occurring during that period. We demonstrate the applicability of the sensor to identify incurred pH changes in a river water sample during an interval of 2 h. This approach is promising for achieving deployable sensors to monitor ion activity relative to a defined threshold during a time interval with minimal electronic components in a self-powered design.


Assuntos
Eletrônica , Eletrodos , Potenciometria
13.
Anal Chim Acta ; 1176: 338756, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34399898

RESUMO

The modulation of the ion-fluxes across a polymeric membrane is important for designing attractive methodologies. As an alternative to the commonly used dynamic electrochemistry approaches, light can be used as an external stimulus and provides a very convenient way to manipulate ions release and/or extraction into a polymeric membrane. Herein, we designed a solid-contact polymeric membrane ion-selective sensor that exhibits dynamic response by light irradiation at 375 nm. The electrode membrane contains a light-sensitive lipophilic salt (bis(4-tert-butylphenyl)iodonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (R+-R-, BTDT-TFPB) instead of traditional ion exchanger. Under light illumination, the decomposition of the lipophilic cation makes the membrane with ion-exchange properties. The solid-contact ion-selective electrodes based on potentiometry and constant potential coulometry have been explored for direct ion sensing. Copper was selected as a mode analyte and can be determined at micromole levels. The proposed dynamic ion sensors show promise for on-demand ion sensing.


Assuntos
Eletrodos Íon-Seletivos , Membranas Artificiais , Cátions , Eletrodos , Polímeros , Potenciometria
14.
Sensors (Basel) ; 21(16)2021 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-34450843

RESUMO

Screen-printed sensing electrodes attract much attention for water pollution monitoring due to their small size, physical and chemical durability, and low cost. This paper presents the fabrication and broad potentiometric characterization of RuO2 pH sensing electrodes deposited by screen printing on alumina substrates and sintered in the 800-900 °C temperature range. All the fabricated electrodes showed close to Nernstian sensitivity, good linearity, fast response, small drift, low hysteresis, and low cross-sensitivity toward various interfering cations and anions. Furthermore, decreasing the sintering temperature led to better adhesion of the RuO2 layer and a negligible response to interfering ions. The measurements in real-life samples from different water sources showed that the fabricated electrodes are on par with conventional glass electrodes with a maximum deviation of 0.11 pH units, thus indicating their potential for application in water quality monitoring.


Assuntos
Qualidade da Água , Água , Eletrodos , Concentração de Íons de Hidrogênio , Potenciometria
15.
Anal Chem ; 93(33): 11525-11531, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34378909

RESUMO

Wearable epidermal sensors that can provide noninvasive and continuous analysis of metabolites and electrolytes in sweat have great significance for healthcare monitoring. This study reports an epidermal sensor that can wirelessly, noninvasively, and potentiometrically analyze metabolites and electrolytes. Potentiometry-based ion-selective electrodes (ISE) are most widely used for detecting electrolytes, such as Na+ and K+. We develop an enzyme-based glucose ISE for potentiometric analysis of sweat glucose. The glucose ISE sensor is obtained by modifying a glucose oxidase layer (GOD) on an H+ ISE sensor. GOD catalyzes glucose to generate H+. The generated H+ passes through the H+ selective membrane to change the potential of the electrode. We have fully examined the limit of detection, detecting range, and stability of our epidermal sensor. Meanwhile, using this epidermal sensor, we can easily analyze the relationship between blood glucose and sweat glucose. The concentration curve of sweat glucose can represent blood glucose concentration, significantly contributing to sports and chronic disease monitoring.


Assuntos
Técnicas Biossensoriais , Suor , Eletrodos , Eletrólitos , Glucose Oxidase , Eletrodos Íon-Seletivos , Potenciometria
16.
Environ Pollut ; 289: 117882, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34364114

RESUMO

Over two decades have passed since polymeric membrane ion-selective electrodes were found to exhibit sufficiently lower detection limits. This in turn brought a great promise to measure trace level concentrations of heavy metals using potentiometric ion sensors at environmental conditions. Despite great efforts, trace analysis of heavy metals using ion-selective electrodes at environmental conditions is still not commercially available. This work will predominantly concentrate on summarizing and evaluating prospects of using potentiometric ion sensors in view of environmental determination of heavy metals in on-site and on-line analysis modes. Challenges associated with development of reliable potentiometric sensors to be operational in environmental conditions will be discussed and reasoning behind unsuccessful efforts to develop potentiometric on-site and on-line environmental ion sensors will be explored. In short, it is now clear that solely lowering the detection limit of the ion-selective electrodes does not guarantee development of successful sensors that would meet the requirement of environmental matrices over long term usage. More pressing challenges of the properties and the performance of the potentiometric sensors must be addressed first before considering extending their sensitivity to low analyte concentrations. These are, in order of importance, selectivity of the ion-selective membrane to main ion followed by the membrane resistance to parallel processes, such as water ingress to the ISM, light sensitivity, change in temperature, presence of gasses in solution and pH and finally resistance of the ion-selective membrane to fouling. In the future, targeted on-site and on-line environmental sensors should be developed, addressing specific environmental conditions. Thus, ion-selective electrodes should be developed with the intention to be suitable to the operational environmental conditions, rather than looking at universal sensor design validated in the idealized and simple sample matrices.


Assuntos
Metais Pesados , Oligoelementos , Eletrodos Íon-Seletivos , Polímeros , Potenciometria
17.
Molecules ; 26(16)2021 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-34443681

RESUMO

Accurate and precise application of ion-selective electrodes (ISEs) in the quantification of environmental pollutants is a strenuous task. In this work, the electrochemical response of alendronate sodium trihydrate (ALN) was evaluated by the fabrication of two sensitive and delicate membrane electrodes, viz. polyvinyl chloride (PVC) and glassy carbon (GC) electrodes. A linear response was obtained at concentrations from 1 × 10-5 to 1 × 10-2 M for both electrodes. A Nernstian slope of 29 mV/decade over a pH range of 8-11 for the PVC and GC membrane electrodes was obtained. All assay settings were carefully adjusted to obtain the best electrochemical response. The proposed technique was effectively applied for the quantification of ALN in pure form and wastewater samples, acquired from manufacturing industries. The proposed electrodes were effectively used for the determination of ALN in real wastewater samples without any prior treatment. The current findings guarantee the applicability of the fabricated ISEs for the environmental monitoring of ALN.


Assuntos
Indústria Farmacêutica , Resíduos de Drogas/análise , Técnicas Eletroquímicas , Resíduos Industriais/análise , Membranas Artificiais , Osteoporose/tratamento farmacológico , Águas Residuárias/química , Alendronato/análise , Alendronato/química , Carbono/química , Eletrodos , Vidro/química , Concentração de Íons de Hidrogênio , Cloreto de Polivinila/química , Potenciometria , Reprodutibilidade dos Testes
18.
Ann Biol Clin (Paris) ; 79(4): 309-314, 2021 Aug 01.
Artigo em Francês | MEDLINE | ID: mdl-34427563

RESUMO

Natremia is an important biological parameter providing information on the hydration state of patient's intracellular sector. Its measurement can be carried out either by multiparametric laboratory analyser (indirect potentiometry) or delocalized biology analyser (direct potentiometry). The main problem is that for a same patient, these two analysers can give quite different results, hence inducing interpretation problems for clinician. Two one-week study periods comparing the variations in blood sodium levels produced by these automatic analysers were carried out in two intensive care units of Clermont-Ferrand University Hospital. During the second study period, a protocol for collecting blood samples was applied in order to improve the pre-analytical conditions. Between the two weeks of studies, the median of the differences in natremia was significantly reduced, going from 4 mmol/L to 2 mmol/L (p < 0.001), as was the proportion of patients with large differences in sodium levels (strictly higher than 3 mmol/L) going from 51% to 24.8% (p < 0.001). The patients still presenting large variations in sodium had a median of proteins significantly lower than patients with deviations less than or equal to 3 mmol/L: 58.1 g/L against 62.25 g/L respectively (p < 0.001) leading to pseudo-hypernatremia (indirect potentiometry). Despite a significant reduction in differences linked to the application of good preanalytical practices, some patients nonetheless presented a major difference in natremia due to the difference of technique (variations in the lipidoprotein phase of the plasma of intensive care patients) and to the measurement uncertainties.


Assuntos
Eletrodos Íon-Seletivos , Fase Pré-Analítica , Humanos , Unidades de Terapia Intensiva , Potenciometria , Sódio
19.
Anal Chem ; 93(29): 10065-10074, 2021 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-34263595

RESUMO

Reference electrodes must maintain a well-defined potential for long periods of time to be useful. The silver/silver chloride (Ag/AgCl) reference electrode is arguably the most widely used reference electrode, but it leaks silver and chloride ions into the sample solution through the porous frit over time. Further, the porous frit makes miniaturization to the micro- and nanoscale challenging. Here, we present an alternative, where the traditional Ag/AgCl reference electrode porous frit is replaced by a conductive wire, preventing ion leakage and allowing miniaturization to the microscale. Charge balance is maintained through a closed bipolar electrochemical mechanism, where faradaic processes occur on each end of the sealed wire. Using the above design, we demonstrate the efficacy of the leakless, bipolar reference electrode (BPRE) and miniaturize it to the microscale (µ-leakless BPRE). Importantly, we demonstrate that leakless and µ-leakless BPREs behave the same as commercial reference electrodes during potentiometric measurements and leakless BPREs perform similarly during voltammetric measurements on ultramicroelectrodes. We demonstrate that the drift during voltammetry using a leakless BPRE on a macroelectrode is slightly more appreciable compared to the drift seen with a commercial reference electrode. We detail design principles for the use of leakless BPREs in nonaqueous solvents and in sealing other conductive materials (e.g., gold and carbon). Using mass spectrometry, we show that the maximum leakage of methylene blue is 0.36 fmol/s, at least 2 orders of magnitude smaller than that of commercial reference electrodes. Finally, we demonstrate the efficacy of using leakless BPREs in potentiometric glucose sensing.


Assuntos
Transtorno Bipolar , Eletrodos , Humanos , Miniaturização , Potenciometria , Prata
20.
Sensors (Basel) ; 21(13)2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34210087

RESUMO

We report on the development of a simple and cost-effective potentiometric sensor array that is based on manual "drawing" on the polymeric support with the pencils composed of graphite and different types of zeolites. The sensor array demonstrates distinct sensitivity towards a variety of inorganic ions in aqueous media. This multisensor system has been successfully applied to quantitative analysis of 100 real-life surface waters sampled in Mahananda and Hooghly rivers in the West Bengal state (India). Partial least squares regression has been utilized to relate responses of the sensors to the values of different water quality parameters. It has been found that the developed sensor array, or electronic tongue, is capable of quantifying total hardness, total alkalinity, and calcium content in the samples, with the mean relative errors below 18%.


Assuntos
Nariz Eletrônico , Qualidade da Água , Análise dos Mínimos Quadrados , Potenciometria , Rios
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