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1.
J Colloid Interface Sci ; 560: 817-824, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31711668

RESUMO

In this study, ultrathin and defect-free graphene (Gr) sheets were prepared through a fluid dynamics-induced shear exfoliation method using graphite. The high hydrophobicity and surface area of Gr make it attractive as a solid-contact ion-to-electron transducer for potentiometric K+ sensors, in which the electrodes are fabricated through a screen-printing process. The electrochemical characterization demonstrates that Gr solid contact results in a high double-layer capacitance, potential stability, and strong resistance against water layer, gases, and light. The Gr-based K+ sensors showed a Nernstian slope of 53.53 mV/log[K+] within a linear concentration range of 10-1-10-4 M, a low detection limit of 10-4.28 M, a fast response time of ~8 s, good repeatability, and excellent long-term stability. Moreover, the Gr-based K+ sensors provided accurate ion concentrations in actual samples of human sweat and sports drinks.


Assuntos
Técnicas Biossensoriais/instrumentação , Eletroquímica/instrumentação , Eletrodos , Grafite/química , Potássio/análise , Potenciometria/métodos , Suor/metabolismo , Capacitância Elétrica , Bebidas Energéticas/análise , Humanos , Interações Hidrofóbicas e Hidrofílicas , Potenciometria/instrumentação , Transdutores
2.
Sensors (Basel) ; 19(24)2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31817537

RESUMO

Electronic tongue systems equipped with cross-sensitive potentiometric sensors have been applied to pharmaceutical analysis, due to the possibility of various applications and developing new formulations. Many studies already proved the complementarity between the electronic tongue and classical analysis such as dissolution tests indicated by Pharmacopeias. However, as a new approach to study pharmaceuticals, electronic tongues lack strict testing protocols and specification limits; therefore, their results can be improperly interpreted and inconsistent with the reference studies. Therefore, all aspects of the development, measurement conditions, data analysis, and interpretation of electronic tongue results were discussed in this overview. The critical evaluation of the effectiveness and reliability of constructed devices may be helpful for a better understanding of electronic tongue systems development and for providing strict testing protocols.


Assuntos
Preparações Farmacêuticas/análise , Potenciometria/métodos , Dipirona/análise , Composição de Medicamentos , Nariz Eletrônico , Eletrodos Íon-Seletivos , Potenciometria/instrumentação , Análise de Componente Principal , Pseudoefedrina/análise , Temperatura
3.
Anal Chim Acta ; 1091: 103-111, 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31679563

RESUMO

This work demonstrates an application of the new materials, sponges, for the use in microfluidic solution sampling integrated with ion-selective electrodes. The microfluidic sponge-based sampling was developed and studied as novel sampling and sample handling method to serve as alternative for microfluidic paper- and textile-based sampling for ion analysis in various environmental (Cd2+, Pb2+ and pH) and clinically (K+, Na+, Cl-) relevant samples. Three types of polyurethane, cellulose and natural sponges were used as substrates for microfluidic solution sampling. Polyurethane based sponge was found to have low heavy metal sorption capacity thus it was recognized as suitable for microfluidic sampling coupled with solid-state as well as solid-contact ion-selective electrodes. The application of sponge-based microfluidic sampling, contrary to previous findings of paper- and textile-based microfluidic sampling, allowed measurements of heavy metals without prior modification of the sampling substrate. Finally, the determination of potassium, sodium and chloride in wastewater sludge and sweat samples done with sponge-based microfluidic sampling integrated with ISEs was found similar to analysis done by ICP-OES and IC.


Assuntos
Celulose/química , Cloretos/análise , Poliuretanos/química , Potássio/análise , Sódio/análise , Humanos , Eletrodos Íon-Seletivos , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Potenciometria/instrumentação , Potenciometria/métodos , Solo/química , Suor/química , Águas Residuárias/análise
4.
Analyst ; 144(21): 6432-6437, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31584576

RESUMO

An electrochemical platform was proposed for highly sensitive and selective analysis of sialic acid based on molecularly imprinted polymers (MIPs), which were electropolymerized with the monomer molecules of 3-aminophenylboronic acid (ABA) on a carbon cloth (CC) electrode in the presence of template molecules. The fabricated sensor, named the PABA/CC-based MIP electrode, could be used for the detection of sialic acid because the reversible and covalent boronic acid-diol binding was sensitive to the electrochemical potential of the prepared sensor. The utilization of a CC film as the substrate could improve the sensitivity due to its good electrical conductivity and large surface area. Under the optimized conditions, a good relationship between the change in potential and the concentration of sialic acid was obtained in the range from 40 µM to 440 µM with a detection limit of 0.5 µM. The resulting MIP sensor also displayed good selectivity, reproducibility and stability. Moreover, this sensor was successfully applied for the evaluation of the sialic acid level in infant formulas.


Assuntos
Ácidos Borônicos/química , Carbono , Impressão Molecular , Ácido N-Acetilneuramínico/análise , Polímeros/síntese química , Potenciometria/instrumentação , Têxteis , Ácido 4-Aminobenzoico/química , Humanos , Concentração de Íons de Hidrogênio , Lactente , Fórmulas Infantis/química , Fenômenos Mecânicos , Polímeros/química
5.
Biosens Bioelectron ; 146: 111750, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31605989

RESUMO

Modulated light-activated electrochemistry (MLAE) at semiconductor/liquid interfaces derived from light-addressable potentiometric sensor (LAPS) and light-activated electrochemistry (LAE) for addressable photoelectrochemical sensing has been proposed as a new sensor platform. In this system, a bias voltage is applied to create a depletion layer at the silicon/electrolyte interface. Meanwhile, intensity-modulated light illuminates the movable electrode to generate electron/hole pairs and causes a detectable local AC photocurrent. The AC measurement showed a higher signal-to-noise ratio (SNR) of photocurrents compared to the traditional DC response, while a steeper photocurrent-voltage (I-V) curve than that of LAPS with an insulating layer was obtained. Furthermore, to stabilize and functionalize the silicon substrate, metal-organic framework (MOF) nanoparticles were grown in-situ on the silicon electrode. The successful modification was validated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The AC photocurrent increased as a result of the adsorption of negatively charged DNA, which contributed to the enhancement of the cathodic reduction process at the semiconductor electrodes, indicating a different response mechanism of MLAE from LAPS. The results obtained demonstrate the potential of MOF functionalized MLAE as a robust platform for light-addressable DNA chips with high sensitivity and specificity.


Assuntos
DNA/análise , Estruturas Metalorgânicas/química , Análise de Sequência com Séries de Oligonucleotídeos/instrumentação , Silício/química , Técnicas Biossensoriais/instrumentação , Desenho de Equipamento , Ácidos Nucleicos Imobilizados/química , Luz , Potenciometria/instrumentação
6.
Methods Mol Biol ; 2027: 151-161, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31309479

RESUMO

Preparation of potentiometric and amperometric sensors with thin-film membranes based on molecularly imprinted polymers (MIP) is described. Spherical MIP microparticles with diameter below 1 µm are suitable for incorporation into the sensing membrane by the deposition of a conducting polymer on the electrode surface. This is achieved through electropolymerization from the suspension of MIP particles in monomer solution. Procedures of the synthesis of MIP particles, preparation of sensing membranes, and analytical application of potentiometric and amperometric sensors with MIP-modified membranes are described.


Assuntos
Impressão Molecular/métodos , Polímeros/química , Eletricidade , Eletrodos , Polimerização , Potenciometria/instrumentação
7.
Methods Mol Biol ; 2027: 181-194, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31309482

RESUMO

The procedures for response standardization in "electronic tongue" (ET) studies are described. The construction of reliable multivariate calibration for "electronic tongue" requires the analysis of a large number of representative samples both with ET and reference techniques. This is a laborious and expensive process. Long-term sensor array operation leads to the changes in sensor response characteristics and thus invalidates the multivariate predictive models. Moreover, due to the individual parameters of each sensor in different sensor arrays, it is not possible to use the calibration model for one system together with the data acquired by another system, even if they have the same sensors. Both of these issues lead to the necessity of frequent sensor array calibration which would be ideal to avoid. Instead of recalibration, these two problems can be handled using mathematical methods intended for sensor response standardization. This chapter describes two popular methods of standardization which can be used for both drift correction and calibration transfer. Thus, significant efforts on measuring representative sample sets for sensor array recalibration can be avoided.


Assuntos
Nariz Eletrônico/normas , Modelos Químicos , Calibragem , Potenciometria/instrumentação , Potenciometria/métodos , Potenciometria/normas , Padrões de Referência , Análise Espectral/instrumentação , Análise Espectral/métodos , Análise Espectral/normas
8.
Anal Sci ; 35(10): 1111-1115, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31231090

RESUMO

Potentiometric glutathione (GSH) sensors were fabricated using a molecularly imprinted polymer prepared from GSH, methacrylic acid (MAA), and ethylene glycol dimethacrylate as the template molecule, functional monomer, and cross-linker, respectively. Five GSH sensors were prepared with different ratios of GSH to MAA. Their potential responses were measured in a GSH aqueous solution using Ag/AgCl as the reference electrode. A GSH sensor prepared with a GSH:MAA ratio of 2:32 had the best responsivity, while the sensor synthesized from a non-imprinted polymer prepared without GSH (NIP sensor) showed a potential response value of almost zero after the addition of GSH. The ratio of the potential responses of the GSH sensor to the NIP sensor was 8.21. Additionally, the GSH sensor had good linearity over a GSH concentration range of 1 × 10-5 to 2 × 10-4 mol L-1. The GSH sensor provided good quantification and high specificity for GSH and is expected to be applicable for easy and direct determinations of GSH.


Assuntos
Glutationa/análise , Impressão Molecular , Polímeros/síntese química , Potenciometria/instrumentação , Glutationa/química , Metacrilatos/química , Polímeros/química
9.
Biosens Bioelectron ; 141: 111317, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31226602

RESUMO

This work reports a new paper-based sensing platform and its application in a label-free potentiometric immunosensor for Salmonella typhimurium detection based on the blocking surface principle. A paper-based strip electrode was integrated with a filter paper pad which acted as a reservoir of the internal solution. The design offers a convenient platform for antibody immobilization and sampling, proving also that is a simple and affordable methodology to control an ionic flux through a polymer membrane. Two different immunosensing interfaces were assembled on the developed paper-strip electrode. The simplest interface relied on direct conjugation of the antibody to the polymer membrane and the second one resorted to an intermediate layer of a polyamidoamine dendrimer, with an ethylenediamine core from the fourth generation. Electrochemical impedance spectroscopy was used to assess the successive interface modification steps and the resulting analytical performance of both immunosensors was compared. For such, the potential shift derived from the blocking effect of the ionic flux caused by antigen-antibody conjugation was correlated with the logarithm of the Salmonella typhimurium concentration in the sample. In optimized conditions, a limit of detection of 5 cells mL-1 was achieved. As a proof-of-concept, the proposed method was applied to apple juice samples, demonstrating to be a suitable prototype to be used in real scenarios in useful time (<1 h assay).


Assuntos
Técnicas Biossensoriais/instrumentação , Análise de Alimentos/instrumentação , Sucos de Frutas e Vegetais/microbiologia , Potenciometria/instrumentação , Salmonella typhimurium/isolamento & purificação , Anticorpos Imobilizados/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Humanos , Imunoensaio/instrumentação , Limite de Detecção , Papel , Fitas Reagentes/análise , Infecções por Salmonella/microbiologia
10.
Sensors (Basel) ; 19(9)2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31035734

RESUMO

The paper describes a wide-range practical application of the potentiometric multisensor system (MS) (1) for integral safety evaluation of a variety of natural waters at multiple locations, under various climatic conditions and anthropogenic stress and (2) for close to real consistency evaluation of waste water purification processes at urban water treatment plants. In total, 25 natural surface water samples were collected around St. Petersburg (Russia), analyzed as is, and after ultrasonic treatment. Toxicity of the samples was evaluated using bioassay and MS. Relative errors of toxicity assessment with MS in these samples were below 20%. The system was also applied for fast determination of integral water quality using chemical oxygen demand (COD) values in 20 samples of water from river and ponds in Kolkata (India) and performed with an acceptable precision of 20% to 22% in this task. Furthermore, the MS was applied for fast simultaneous evaluation of COD, biochemical oxygen demand, inorganic phosphorous, ammonia, and nitrate nitrogen at two waste water treatment plants (over 320 samples). Reasonable precision (within 25%) of such analysis is acceptable for rapid water safety evaluation and enables fast control of the purification process. MS proved to be a practicable analytical instrument for various real-world tasks related to water safety monitoring.


Assuntos
Nariz Eletrônico , Potenciometria/métodos , Águas Residuárias/análise , Qualidade da Água , Animais , Análise da Demanda Biológica de Oxigênio , Daphnia/efeitos dos fármacos , Processamento Eletrônico de Dados , Análise dos Mínimos Quadrados , Potenciometria/instrumentação , Análise de Componente Principal , Águas Residuárias/toxicidade , Purificação da Água
11.
PLoS One ; 14(3): e0212943, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30840667

RESUMO

The development of new signal systems for electrical biosensors could provide exciting new opportunities for biomedical analysis, pollutant monitoring, and explosive detection. The signal systems for commercial portable sensors involve the integration of a battery and a circuit conditioning system to power an amperometric biosensor. However, this increases the size and complexity of the entire system. In this study, we develop a simple amperometric biosensor that is directly powered by a button cell battery for the detection of lactate. A two-electrode sensing transducer was printed on cardboard or integrated on a ring. It was directly powered by a button cell battery, and connected to a multimeter for current measurement. This sensor showed a sensitive detection range of 0.04762-9.21429 mM and short measuring time of 2 min. These results show that this system can achieve an excellent sensing performance, and the construction of this new sensing system directly powered by a button cell battery offers a new method for further developing a wide range of miniaturized, flexible, portable, or wearable sensing systems, and these could be used in detecting various analytes that are important in medical diagnosis and environmental monitoring.


Assuntos
Técnicas Biossensoriais/instrumentação , Fontes de Energia Elétrica , Ácido Láctico/análise , Técnicas Biossensoriais/métodos , Eletrodos , Estudos de Viabilidade , Limite de Detecção , Miniaturização , Potenciometria/instrumentação , Potenciometria/métodos , Dispositivos Eletrônicos Vestíveis
12.
Sensors (Basel) ; 19(2)2019 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-30658434

RESUMO

Wearable potentiometric sensors have received considerable attention owing to their great potential in a wide range of physiological and clinical applications, particularly involving ion detection in sweat. Despite the significant progress in the manner that potentiometric sensors are integrated in wearable devices, in terms of materials and fabrication approaches, there is yet plenty of room for improvement in the strategy adopted for the sample collection. Essentially, this involves a fluidic sampling cell for continuous sweat analysis during sport performance or sweat accumulation via iontophoresis induction for one-spot measurements in medical settings. Even though the majority of the reported papers from the last five years describe on-body tests of wearable potentiometric sensors while the individual is practicing a physical activity, the medical utilization of these devices has been demonstrated on very few occasions and only in the context of cystic fibrosis diagnosis. In this sense, it may be important to explore the implementation of wearable potentiometric sensors into the analysis of other biofluids, such as saliva, tears and urine, as herein discussed. While the fabrication and uses of wearable potentiometric sensors vary widely, there are many common issues related to the analytical characterization of such devices that must be consciously addressed, especially in terms of sensor calibration and the validation of on-body measurements. After the assessment of key wearable potentiometric sensors reported over the last five years, with particular attention paid to those for medical applications, the present review offers tentative guidance regarding the characterization of analytical performance as well as analytical and clinical validations, thereby aiming at generating debate in the scientific community to allow for the establishment of well-conceived protocols.


Assuntos
Tecnologia Biomédica/instrumentação , Técnicas Biossensoriais/instrumentação , Potenciometria/instrumentação , Dispositivos Eletrônicos Vestíveis , Eletroquímica , Humanos , Iontoforese
13.
ACS Appl Mater Interfaces ; 11(5): 5561-5569, 2019 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-30644715

RESUMO

In this paper, we propose a novel concept of a biointerface, a polymeric nanofilter, for the potentiometric detection of small biomolecules using an extended-Au-gate field-effect transistor (EG-Au-FET). A Au electrode has the potential capability to detect various small biomolecules with ultrasensitivity at nM levels on the basis of a surface redox reaction, but it exhibits no selective response to such biomolecules. Therefore, a suitable polymeric nanofilter is designed and modified on the Au electrode, so that a small target biomolecule reaches the Au surface, resulting in an electrical signal, whereas low-molecular-weight interferences not approaching the Au surface are captured in the polymeric nanofilter. The polymeric nanofilter is composed of two layers. The first layer is electrografted as an anchor layer by a cyclic voltammetry method. Then, a filtering layer is precisely polymerized as the second layer by a photo-mediated surface-initiated atom transfer radical polymerization method. The thickness and density of the polymeric nanofilter are controlled to specifically detect a small target biomolecule with high sensitivity. As a model case, l-cysteine as the small target biomolecule at nM levels is specifically detected by filtering l-DOPA as a low-molecular-weight interference using the polymeric nanofilter-grafted EG-Au-FET on the basis of the following mechanism. The phenylboronic acid (PBA) that copolymerizes with the polymeric nanofilter captures l-DOPA through diol binding, whereas l-cysteine reaches the Au surface through the filter layer. The polymeric nanofilter can also effectively prevent the interaction between biomacromolecules such as albumin and the Au electrode. A platform based on a polymeric nanofilter-grafted EG-Au-FET biosensor is suitable for the ultrasensitive and specific detection of a small biomolecule in biological samples such as tears and sweat, which include small amounts of low-molecular-weight interferences, which generate nonspecific electrical signals.


Assuntos
Técnicas Biossensoriais/instrumentação , Nanoestruturas/química , Nanotecnologia/instrumentação , Potenciometria/instrumentação , Ácidos Borônicos/química , Eletrodos , Desenho de Equipamento , Ouro/química , Levodopa/química , Levodopa/isolamento & purificação , Polimerização , Transistores Eletrônicos
14.
J AOAC Int ; 102(3): 794-800, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30446018

RESUMO

Background: Traditional methods for Lomefloxacin hydrochloride (LOM) determination involve pretreatment steps, which extend analysis time and use hazardous chemicals. Objective: The ability to provide a rapid route without sample pretreatment for quantitative determination of compounds via a low-cost instrument is a challenging task. In this work, a simple potentiometric method was developed to determine the antibacterial LOM via in-house fabricated ion selective electrodes. Methods: Different sensors were fabricated using a poly vinyl chloride-based membrane, potassium tetrakis(4-chlorophenyl) borate as a cation exchanger, and 2-Nitrophenyl octyl ether as a plasticizer (sensor 1). To increase the selectivity of sensor 1, a selective molecular recognition component 2-hydroxypropyl-ß-cyclodextrin was used as ionophore (sensor 2). Results: The proposed method was validated according to International Union of Pure and Applied Chemistry recommendations, in which the proposed sensors show a linear dynamic range from 1 × 10-5 to 1 × 10-2 mol/L, with Nernstian slopes of 55.829 and 58.229 mV/decade for sensors 1 and 2, respectively. It was applied to determine LOM in bulk powder, in different dosage forms, and in plasma with no sample pretreatment. Also, the suggested method can be used as a green, in-line bench top real-time analyzer for in-process monitoring of LOM release from its tablets, under U.S. Food and Drug Administration dissolution regulations, with clear discrimination from common excipients. Results obtained by the proposed potentiometric method were compared with those obtained by a reported HPLC method. Conclusions: The proposed method is considered as a perfect alternative to traditional reported methods for LOM determination.


Assuntos
Antibacterianos/sangue , Fluoroquinolonas/sangue , Química Verde/métodos , 2-Hidroxipropil-beta-Ciclodextrina/química , Antibacterianos/administração & dosagem , Cromatografia Líquida de Alta Pressão/normas , Éteres/química , Fluoroquinolonas/administração & dosagem , Química Verde/instrumentação , Química Verde/normas , Humanos , Eletrodos Íon-Seletivos , Ionóforos/química , Limite de Detecção , Soluções Oftálmicas/análise , Plastificantes/química , Cloreto de Polivinila/química , Potenciometria/instrumentação , Potenciometria/métodos , Potenciometria/normas , Comprimidos/análise , Tetrafenilborato/análogos & derivados , Tetrafenilborato/química
15.
Biosens Bioelectron ; 126: 115-121, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30396018

RESUMO

Bilirubin is predominantly formed in the liver as a result of breakdown of hemoglobin. Knowing the concentration of bilirubin in serum is important in evaluating the health of the liver, and for the diagnosis of hyperbilirubinemia (a condition that afflicts approximately 60% of full-term and 80% of pre-term newborns). This paper describes the design and fabrication of a potentiometric sensor for the determination of free bilirubin in serum. The sensor has a polymeric ion-selective membrane, and selectively measures free ionic bilirubin ("unbound" bilirubin - i.e., bilirubin not complexed to albumin or other complexing agents), in the presence of other anions - chloride, phosphate, pyruvate, deoxycholate, and lactate - also present in serum. The linear response range of the sensor (1.0 mM to 0.10 µM bilirubin, measured in a sodium phosphate buffer with pH 8.6) covers the clinically-relevant concentration of bilirubin in serum (5-500 µM). Free bilirubin could be detected in human blood serum with this potentiometric sensor. The components of the potentiometric bilirubin sensor were embedded in a paper-based device to provide a sensor that is disposable and easy to use, and thus is suitable for applications at the point-of-care. The paper-based potentiometric bilirubin sensor exhibited a response range of 5.0-0.10 mM (sufficient to cover the clinically-relevant concentration of bilirubin in serum). Only 15 µL of sample is required for measurement of the concentration of free bilirubin, and the analysis can be performed in less than two minutes.


Assuntos
Bilirrubina/sangue , Técnicas Biossensoriais/instrumentação , Papel , Potenciometria/instrumentação , Eletrodos , Desenho de Equipamento , Humanos , Hiperbilirrubinemia/sangue , Hiperbilirrubinemia/diagnóstico , Recém-Nascido , Limite de Detecção , Masculino , Sistemas Automatizados de Assistência Junto ao Leito
16.
Talanta ; 192: 103-111, 2019 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-30348364

RESUMO

A novel nano-sized imprinted polymer/multi-walled carbon nanotube (MWCNTs)-based potentiometric sensor is introduced for lactic acid (LA) sensing in dairy products. The imprinted polymer was synthesized using allyl amine (AA) and ethylene glycol dimethacrylate as functional monomer and cross-linker, respectively. It was demonstrated that the amide linkage was created between LA and AA during copolymerization reaction which was finally hydrolyzed when removing template from the synthesized MIP. It was also shown that the MIP cavities, compatible with LA anion, were created during polymerization reaction which influenced the potentiometric response behavior of the MIP-based electrode. This novel potentiometric sensor is a carbon rod electrode, coated with a membrane consisting of the MIP nanoparticles (2.5%), MWCNTs (2%), dibutylphthalate (DBP) (65%), poly-vinyl chloride (PVC) (28.5%) and tetra phenyl phosphonium bromide (TPPB) (2%). The active ion sensed by the electrode is the LA anion formed at elevated pH condition. The sensor exhibited Nernstian slope of 30.3 ±â€¯0.4 mVdecade-1 in the working concentration range of 1.0 × 10-1to 1.0 × 10-6 mol L-1 with detection limit of 7.3 × 10-7 mol L-1. The sensor displayed a stable potential response in the pH range of 5-8 and fast response time of less than 60 s. It exhibited also high selectivity over the interfering species. The proposed sensor was successfully applied for the determination of LA in real samples (milk and yoghurt).


Assuntos
Carbono/química , Ácido Láctico/análise , Impressão Molecular , Nanocompostos/química , Nanotubos de Carbono/química , Polímeros/química , Eletrodos , Tamanho da Partícula , Potenciometria/instrumentação , Propriedades de Superfície
17.
Talanta ; 193: 9-14, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30368303

RESUMO

Graphene is the ''new star'' material for electrochemical sensing. It has unique mechanical, thermal and electrical properties, in addition to its ultra light weight. In the present work we combine for the first time the special features offered by graphene and the advantages of ion selective potentiometric sensors in a single study. We propose two types of sensors, a graphene based carbon paste and a poly vinyl chloride (PVC) based membrane sensors for the analysis of Vilazodone hydrochloride in bulk, human plasma and formula milk samples. Electro active agent is an ion- association complex based on coupling of Vilazodone cationic cite with anionic cite of Molybdate ion in a ratio 1:1. Both sensors are evaluated according to the IUPAC recommendation data, revealing linear response in the concentration range 10-7 - 10-3 and10-8 - 10-3 M with a Nernestian slope 59.89 and 59.91 mV/decade for PVC membrane and Carbon paste sensors, respectively. Both sensors were successfully applied to the analysis of Vilazodone HCl in human plasma and formula milk samples showing good recovery percentage values. Graphene based carbon paste sensor shows several advantages over conventional PVC membrane sensor regarding lower limit of detection, faster response time, longer life time and higher selectivity towards target ion.


Assuntos
Antidepressivos/sangue , Grafite/química , Fórmulas Infantis/análise , Nanocompostos/química , Cloreto de Polivinila/química , Cloridrato de Vilazodona/sangue , Dietilexilftalato/química , Humanos , Concentração de Íons de Hidrogênio , Lactente , Recém-Nascido , Limite de Detecção , Molibdênio/química , Potenciometria/instrumentação , Potenciometria/métodos
18.
ACS Sens ; 3(12): 2581-2589, 2018 12 28.
Artigo em Inglês | MEDLINE | ID: mdl-30398333

RESUMO

The neurotransmitter acetylcholine (ACh) plays a key role in the pathophysiology of brain disorders such as Alzheimer's disease. Understanding the dynamics of ACh concentration changes and kinetics of ACh degradation in the living brain is crucial to unravel the pathophysiology of such diseases and the rational design of therapeutics. In this work, an electrochemical sensor capable of dynamic, label-free, selective, and in situ detection of ACh in a range of 1 nM to 1 mM (with temporal resolution of less than one second) was developed. The sensor was employed for the direct detection of ACh in artificial cerebrospinal fluid and rat brain homogenate, without any prior separation steps. A potentiometric receptor-doped ion-selective electrode (ISE) with selectivity for ACh was designed by taking advantage of the positive charge of ACh. The dynamic range, limit of detection (LOD), and the selectivity of the sensor were optimized stepwise by (i) screening of hydrophobic biomimetic calixarenes to identify receptors that strongly bind to ACh based on shape-selective multitopic recognition, (ii) doping of the ISE sensing membrane with an ACh-binding hydrophobic calixarene to enable selective detection of ACh in complex matrices, (iii) utilizing a hydrophilic calixarene in the inner filling solution of the ISE to buffer the concentration of ACh and, thereby, lower the LOD of the sensor, and (iv) introducing a surface treatment step prior to the measurement by placing the sensor for ∼1 min in a solution of a hydrophilic calixarene to lower the LOD of the sensor even further.


Assuntos
Acetilcolina/líquido cefalorraquidiano , Neurotransmissores/líquido cefalorraquidiano , Potenciometria/métodos , Acetilcolina/química , Animais , Materiais Biomiméticos/química , Química Encefálica , Calixarenos/química , Eletrodos , Interações Hidrofóbicas e Hidrofílicas , Ionóforos/química , Limite de Detecção , Masculino , Neurotransmissores/química , Potenciometria/instrumentação , Ratos Wistar
19.
Anal Chem ; 90(21): 13021-13029, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30335971

RESUMO

Understanding the real-time correlation between chemical patterns and neural processes is critical for deciphering brain function. Voltammetry has enabled this task but with a number of challenges for current-based electrolysis in vivo. Herein, we report galvanic redox potentiometry (GRP) potentially as a universal strategy for in vivo monitoring of neurochemicals, with ascorbic acid (AA) as a typical example. The GRP sensor is constructed on a self-driven galvanic cell configuration, where AA is spontaneously oxidized at the indicating single-walled carbon nanotube-modified carbon fiber electrode (SWNT-CFE), while oxygen reduced at the laccase-modified reference CFE (Lac-CFE). At thermodynamic equilibrium, open-circuit potential (OCP) can be a linear indicator of the concentration of AA. The resulting sensor shows a high selectivity to AA dynamics in the presence of coexisting electroactive neurochemicals, which is mainly determined by the driving force for the cell reaction, as suggested by principal investigation. Sensing sensitivity of this OCP-based GRP method is not affected by nonspecific protein adsorption and electrode fouling. Moreover, a micropipette compartment of the reference electrode is designed to suppress mass crossover and prevent disturbance to oxygen reduction through confinement effect. The in vivo application of the GRP sensor is illustrated by measuring the basal level of cortical AA in live rat brain (230 ± 40 µM) and its dynamics during ischemia/reperfusion. The GRP concept is demonstrated as a prominent method for in vivo, real-time, quantitative analysis of brain neurochemistry.


Assuntos
Ácido Ascórbico/análise , Química Encefálica/fisiologia , Encéfalo/metabolismo , Potenciometria/métodos , Animais , Ácido Ascórbico/química , Fibra de Carbono/química , Eletrodos , Enzimas Imobilizadas/química , Lacase/química , Masculino , Nanotubos de Carbono/química , Oxirredução , Oxigênio/química , Potenciometria/instrumentação , Ratos Sprague-Dawley , Trametes/enzimologia
20.
PLoS One ; 13(9): e0203862, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30252859

RESUMO

Small-holding farmers in the developing world suffer from sub-optimal crop yields because they lack a soil diagnostic system that is affordable, usable, and actionable. This paper details the fabrication and characterization of an integrated point-of-use soil-testing system, comprised of disposable ion-selective electrode strips and a handheld electrochemical reader. Together, the strips and reader transduce soil ion concentrations into to an alphanumeric output that can be communicated via text message to a central service provider offering immediate, customized fertilizer advisory. The solid-state ion-selective electrode (SS-ISE) strips employ a two-electrode design with screen-printable carbon nanotube ink serving as the electrical contacts for the working and reference electrodes. The working electrode comprises a plasticizer-free butyl acrylate ion-selective membrane (ISM), doped with an ion-selective ionophore and lipophilic salt. Meanwhile, the reference electrode includes a screen-printed silver-silver chloride ink and a polyvinyl-butyral membrane, which is doped with sodium chloride for stable reference potentials. As a proof of concept, potassium-selective electrodes are studied, given potassium's essential role in plant growth and reproduction. The ISE-based system is reproducibly manufactured to yield a Nernstian response with a sub-micromolar detection limit (pK+ of 5.18 ± 0.08) and near-Nernstian sensitivity (61 mV/decade) in the presence of a 0.02 M strontium chloride extraction solution. Analysis of soil samples using the printed electrodes and reader yielded a correlation coefficient of 𝑅2 = 0.89 with respect to values measured via inductively coupled plasma atomic emission spectroscopy (ICP-AES). The reliable performance of this system is encouraging toward its deployment for soil nutrient management in resource-limited environments.


Assuntos
Potenciometria/instrumentação , Solo/química , Eletrodos , Equipamentos e Provisões , Eletrodos Íon-Seletivos , Limite de Detecção , Potenciometria/métodos
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