Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.141
Filtrar
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.
Food Chem ; 309: 125703, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31670132

RESUMO

A new version of the hybrid potentiometric method (HPM) for evaluating the antioxidant activity (AOA) of fruits and vegetables, which we called contact (CHPM), is proposed. A screen-printed electrode pair coated by a membrane impregnated with a mediator serves as a sensor system. The potential shift, which is observed when the sensor system is exposed to the sample slice is used as a source of information. CHPM provides reproducible and correct results: relative standard deviation does not exceed 8.4% and recovery of model antioxidant at close to 100%. The AOA values of fruits and vegetables found by CHPM are in the range of 1-21 µmol-eq/g. Correlation between the AOA of slices and suspensions is found. The proposed CHPM can be used in on-site and in situ formats.


Assuntos
Antioxidantes/análise , Frutas/química , Potenciometria/métodos , Verduras/química , Eletrodos , Frutas/metabolismo , Alho/química , Alho/metabolismo , Verduras/metabolismo
3.
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
4.
Sensors (Basel) ; 19(24)2019 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-31842267

RESUMO

The detection of bacterial deoxyribonucleic acid (DNA) is of great significance in the quality control of food and water. In this study, a light-addressable potentiometric sensor (LAPS) deposited with highly oriented ZnO nanorod arrays (NRAs) was used for the label-free detection of single-stranded bacterial DNA (ssDNA). A functional, sensitive surface for the detection of Escherichia coli (E. coli) O157:H7 DNA was prepared by the covalent immobilization of the specific probe single-stranded DNA (ssDNA) on the LAPS surface. The functional surface was exposed to solutions containing the target E. coli ssDNA molecules, which allowed for the hybridization of the target ssDNA with the probe ssDNA. The surface charge changes induced by the hybridization of the probe ssDNA with the target E. coli ssDNA were monitored using LAPS measurements in a label-free manner. The results indicate that distinct signal changes can be registered and recorded to detect the target E. coli ssDNA. The lower detection limit of the target ssDNA corresponded to 1.0 × 102 colony forming units (CFUs)/mL of E. coli O157:H7 cells. All the results demonstrate that this DNA biosensor, based on the electrostatic detection of ssDNA, provides a novel approach for the sensitive and effective detection of bacterial DNA, which has promising prospects and potential applications in the quality control of food and water.


Assuntos
Técnicas Biossensoriais , DNA Bacteriano/isolamento & purificação , Infecções por Escherichia coli/diagnóstico , Escherichia coli O157/isolamento & purificação , DNA Bacteriano/genética , Infecções por Escherichia coli/microbiologia , Escherichia coli O157/genética , Escherichia coli O157/patogenicidade , Humanos , Luz , Nanotubos/química , Potenciometria/métodos
5.
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
6.
J Food Sci ; 84(8): 2165-2170, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31313309

RESUMO

To determine the total acidity in freshly squeezed fruit juice, we miniaturized the potentiometric titrations and achieved better accuracy compared with titrations from a conventional pH probe. The improvement was the result of a higher jump in pH at the endpoint due to a reduction in the dilutions of both the titrand and titrant. A conventional pH probe requires more than 50 mL of titrand, which can lead to a 25000-fold dilution of the titrant when adding the titrant at 2 µL intervals. Conversely, when the volume of the titrand can be reduced to 1 mL, the dilution is only 500-fold, which results in a higher jump in pH at the endpoint. The concentration of the titrant, NaOH, was optimized by titrating sample solutions containing 25 and 50 mM of citric acid. The addition of 5 M NaOH in intervals of 2 µL led to a more accurate endpoint for both 25 and 50 mM citric acid solutions. Miniaturization of the titration process is advantageous in terms of portability, accuracy, and in requiring less consumption of a sample, thereby simplifying the process of repeat measurements that are helpful in evaluating the precision of analytical results. Practical samples of squeezed fruit juices were titrated via three methods that showed no significant differences: classic titrimetry with an indicator, conventional potentiometry, and miniaturized potentiometry. This process would be effective for use in the field and in developing countries. PRACTICAL APPLICATION: The total acidity of fruits and fruit juices is an important indicator of quality and is generally expressed in terms of the citric acid content. However, a standard potentiometric titration requires a large sample volume, which makes it difficult to assess dispersion of the acidity for individual fruits. The results of this study indicate that the use of miniaturized potentiometric titration could benefit food chemistry in many developing countries in addition to opening new fields of food chemistry such as on-site quality control of citrus fruit and evaluation of variations in quality.


Assuntos
Ácido Cítrico/análise , Sucos de Frutas e Vegetais/análise , Potenciometria/métodos , Citrus/química , Frutas/química , Concentração de Íons de Hidrogênio , Titulometria/métodos
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.
Prep Biochem Biotechnol ; 49(9): 868-875, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31219372

RESUMO

Non-covalent complexes of urease/polyethylene glycol (PEG)-aldehyde were synthesized using regular molar ratios of urease and PEG-aldehyde at room temperature. The physical properties of the non-covalent complexes were analyzed in order to investigate the impact of coupling ratio, temperature, pH, storage stability, and thermal stability. Urease activity was analyzed by UV-Vis spectrophotometer at 630 nm. The results showed that the strongest thermal resistance was obtained using nU/nPEG:1/1 (mg/mL) complex within all molar ratios tested. The enzymatic activity of nU/nPEG:1/1 complex doubled the activity of the free enzyme. Therefore, this complex was chosen to be used in the analyses. When coupled with PEG-aldehyde, urease exhibited improved activity between pH 4.0-9.0 and the optimum pH was found to be 7.0. The thermal inactivation results of the complex demonstrated that higher activity remained (40%) when compared with the free enzyme (10%) at 60 °C. The storage stability of the non-covalent complex was 4 weeks which was greater than the storage stability of the free enzyme. A kinetic model was suggested in order to reveal the mechanism of enzymatic conversion. Potentiometric urea biosensor was prepared using two different membranes: carboxylated poly vinyl chloride (PVC) and palmitic acid containing PVC. The potentiometric responses of both sensors were tested against pH and temperature and the best results were obtained at pH 7.0 and 20-30 °C. Also, selectivity of the suggested biosensors toward Na+, Li+ Ca2+, and K+ ions was evaluated and the reproducibility responses of the urea biosensors were measured with acceptable results.


Assuntos
Técnicas Biossensoriais/métodos , Enzimas Imobilizadas/química , Ureia/sangue , Urease/química , Aldeídos/química , Canavalia/química , Canavalia/enzimologia , Estabilidade Enzimática , Humanos , Concentração de Íons de Hidrogênio , Limite de Detecção , Polietilenoglicóis/química , Potenciometria/métodos , Temperatura
9.
Sensors (Basel) ; 19(11)2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31174361

RESUMO

The skin is a natural barrier between the external and internal environment. Its protective functions and the relationship of its state with the state of health of the organism as a whole are very important. It is known that oxidant stress (OS) is a common indicator of health status. This paper describes a new sensory system for monitoring OS of the skin using antioxidant activity (AOA) as its criteria. The contact hybrid potentiometric method (CHPM) and new electrochemical measuring scheme were used. A new sensory system, including disposable modified screen-printed carbon and silver electrodes covered by membrane impregnated by mediator, was developed. Its informative ability was demonstrated in the evaluation of the impact of fasting, consumption of food and food enriched by vitamins (antioxidants) on skin AOA. This device consisting of a sensory system and potentiometric analyzer can be used in on-site and in situ formats.


Assuntos
Antioxidantes/isolamento & purificação , Técnicas Biossensoriais , Potenciometria/métodos , Prata/química , Antioxidantes/química , Carbono/química , Humanos
10.
J Chromatogr A ; 1602: 326-340, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31227359

RESUMO

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.


Assuntos
Cromatografia Líquida/métodos , Potenciometria/métodos , Ânions , Cátions , Eletrodos
11.
Biosens Bioelectron ; 139: 111332, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31132723

RESUMO

Applying biosensors for evaluation of the extracellular acidification of microorganisms in various biotechnological fermentation processes is on demand. An early stage detection of disturbances in the production line would avoid costly interventions related to metabolically inactive microorganisms. Furthermore, the determination of the number of living cells through cell plating procedure after cultivations is known as time- and material-consuming. In this work, a differential light-addressable potentiometric sensor (LAPS) system was developed to monitor the metabolic activity of Corynebacterium glutamicum (C. glutamicum ATCC13032) as typical microorganism in fermentation processes. In this context, the number of living cells in suspensions was directly determined utilizing the read-out principle of the LAPS system. The planar sensor surface of the LAPS design allows to fixate 3D-printed multi-chamber structures, which enables differential measurements. In this way, undesirable external influences such as pH variations of the medium and sensor signal drift can be compensated.


Assuntos
Técnicas Biossensoriais/métodos , Corynebacterium glutamicum/isolamento & purificação , Potenciometria/métodos , Corynebacterium glutamicum/metabolismo , Meios de Cultura/química , Fermentação , Concentração de Íons de Hidrogênio , Luz
12.
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
13.
Methods Enzymol ; 620: 1-25, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31072483

RESUMO

A key factor for flavoenzyme activity is the reduction potential of the bound flavin. The reduction potentials of protein-bound flavins span approximately a 500-mV range consistent with flavoenzymes having critical roles in metabolism and a variety of biological processes. Redox potentials of flavoenzymes have traditionally been determined using an electrode-based system with either direct or indirect electrochemical coupling between the protein and the working electrode. An electrode independent method, however, is also now commonly used and involves calculating the unknown flavin reduction potential of the protein from the known reduction potential of a reference or indicator dye. Here, the "classic" potentiometric method and the xanthine/xanthine oxidase methods are described. Both methods rely on equilibrium between protein-bound flavin and redox dyes. The potentiometric method measures the equilibrated redox potential of the protein-dye mixture whereas the xanthine/xanthine oxidase technique relies on slow continuous enzymatic reduction to maintain a constant equilibrium between the protein and the dyes. Because electrochemical equipment is not required, the xanthine/xanthine oxidase method is more accessible and convenient for researchers seeking to determine reduction potentials of flavoproteins or other biological redox centers such as hemes. The xanthine/xanthine oxidase method has been used to determine flavin reduction potentials from +132 to -417mV, demonstrating it is suitable for characterizing the redox properties of most flavoproteins.


Assuntos
Ensaios Enzimáticos/métodos , Benzil Viologênio/química , Flavinas/química , Flavoproteínas/química , Indicadores e Reagentes/química , Oxirredução , Paraquat/química , Potenciometria/métodos , Xantina/química , Xantina Oxidase/química
14.
PLoS One ; 14(4): e0214580, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30990847

RESUMO

A potentiometric whole cell biosensor based on immobilized marine bacterium, Pseudomonas carrageenovora producing κ-carrageenase and glycosulfatase enzymes for specific and direct determination of κ-carrageenan, is described. The bacterial cells were immobilized on the self-plasticized hydrogen ion (H+)-selective acrylic membrane electrode surface to form a catalytic layer. Hydrogen ionophore I was incorporated in the poly(n-butyl acrylate) [poly(nBA)] as a pH ionophore. Catalytic decomposition of κ-carrageenan by the bienzymatic cascade reaction produced neoagarobiose, an inorganic sulfate ion and a proton. The latter was detectable by H+ ion transducer for indirect potentiometric quantification of κ-carrageenan concentration. The use of a disposable screen-printed Ag/AgCl electrode (SPE) provided no cleaning requirement and enabled κ-carrageenan detection to be carried out conveniently without cross contamination in a complex food sample. The SPE-based microbial biosensor response was found to be reproducible with high reproducibility and relative standard deviation (RSD) at 2.6% (n = 3). The whole cell biosensor demonstrated a broad dynamic linear response range to κ-carrageenan from 0.2-100 ppm in 20 mM phosphate buffer saline (PBS) at pH 7.5 with a detection limit at 0.05 ppm and a Nernstian sensitivity of 58.78±0.87 mV/decade (R2 = 0.995). The biosensor showed excellent selectivity towards κ-carrageenan compared to other types of carrageenans tested e.g. ι-carrageenan and λ-carrageenan. No pretreatment to the food sample was necessary when the developed whole cell biosensor was employed for direct assay of κ-carrageenan in dairy product.


Assuntos
Técnicas Biossensoriais , Carragenina/análise , Potenciometria/métodos , Pseudomonas/metabolismo , Algoritmos , Proteínas de Bactérias/metabolismo , Células Imobilizadas/metabolismo , Meios de Cultura , Eletrodos , Hidrogênio , Íons , Cinética , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Fatores de Tempo
15.
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
16.
Sensors (Basel) ; 19(2)2019 Jan 12.
Artigo em Inglês | MEDLINE | ID: mdl-30642018

RESUMO

Piperazine-based compounds bearing two phenylboronic acid or two benzoxaborole groups (PBPA and PBBB) were applied as dopamine receptors in polymeric membranes (PVC/DOS) of ion-selective electrodes. The potentiometric sensitivity and selectivity of the sensors towards dopamine were evaluated and compared with the results obtained for 2-phenylethylamine. Since the developed electrodes displayed strong interference from 2-phenylethylamine, single-molecule geometry optimizations were performed using the density functional theory (DFT) method in order to investigate the origin of dopamine/2-phenylethylamine selectivity. The results indicated that phenylboronic acid and benzoxaborole receptors bind dopamine mainly through the dative B⁻N bond (like 2-phenylethylamine) and the potentiometric selectivity is mainly governed by the higher lipophilicity of 2-phenylethylamine.


Assuntos
Técnicas Biossensoriais/métodos , Dopamina/isolamento & purificação , Fenetilaminas/isolamento & purificação , Potenciometria/métodos , Boro/química , Ácidos Borônicos/química , Dopamina/química , Eletrodos Íon-Seletivos , Membranas Artificiais , Fenetilaminas/química , Piperazina/química , Cloreto de Polivinila/química
17.
ACS Sens ; 4(2): 413-420, 2019 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-30608656

RESUMO

Recombinant human myelin basic protein (rhMBP) produced in the milk of transgenic cows was found exclusively associated with milk caseins. This hindered its direct determination without extensive sample pretreatment. Here, a label-free potentiometric immunosensor was developed and validated for the determination of rhMBP. An ion flux was generated under zero-current based on surface blocking of the polymeric membrane ion-selective electrode by anti-hMBP antibody and tetrabutylammonium bromide as a marker ion. The immunosensor was successfully employed in the quantitative determination of hMBP in the range of 0.10-20.00 µg/mL with a limit of detection of 50.00 ng/mL. The applicability of the passive ion flux immunosensor for determination of target analyte in complex matrices was investigated. Downstream purification of rhMBP from the milk of transgenic cows was achieved using cation exchange chromatography, immobilized metal affinity chromatography, and immunoaffinity chromatography. The specificity of the immunosensor along with matrix effect of milk proteins were demonstrated. Results obtained using the rhMBP immunosensor were further cross-validated using an orthogonal testing protocol assembled of RP-HPLC and SE-HPLC. It should be noted that the proposed ion flux immunosensor provided a feasible and specific tool for monitoring rhMBP concentration/purity, immunogenic activity, and stability. Such approach provides an attractive economic alternative to sophisticated biosensors required for in-process quality control of biopharmaceutical products.


Assuntos
Técnicas Biossensoriais/métodos , Imunoensaio/métodos , Leite/metabolismo , Bainha de Mielina/metabolismo , Potenciometria/métodos , Proteínas Recombinantes/metabolismo , Animais , Animais Geneticamente Modificados , Bovinos , Humanos , Bainha de Mielina/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação
18.
Anal Chim Acta ; 1046: 69-76, 2019 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-30482304

RESUMO

For the first time, the dependence of a redox potential change during a reaction of peroxyl radical generation and their interaction with antioxidants was studied. A regular change of a potential is due to oxidation of an antioxidant by initiating peroxyl radicals accompanied by an electron transfer. An original direct method for determining induction periods, inhibition coefficients and an antiradical capacity using the potentiometric method is proposed. Using the proposed approach the induction periods and the inhibition coefficients of various OH, NH, SH containing antioxidants were determined. The antiradical capacity of a herbal extract was studied. A high degree of correlation with a DPPH assay was obtained. RSD results obtained using the proposed approach do not exceed 7%.


Assuntos
Peróxidos/análise , Potenciometria/métodos , Transporte de Elétrons
19.
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
20.
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
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA