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1.
Food Chem ; 316: 126352, 2020 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-32062232

RESUMO

This study investigates the relationship between the two main forms of Cu in wine and their impact on the rate of oxygen consumption. The Cu forms were differentiated by medium exchange constant current stripping potentiometry, which classified the Cu as either bound to sulfide or not. Oxygen consumption rates were determined in red, white and model wines after saturation with oxygen. The results for white wines showed that the oxygen consumption was sensitive to the non-sulfide-bound Cu concentration when ascorbic acid was present, and the first order rates ranged from 0.02 to 0.11 h-1. However, the same was not true for wines without added ascorbic acid that showed little influence of Cu form on oxygen decay rates. Cu forms were also found to significantly change in some wines during the oxygen decay experiment. Ascorbic acid is critical in enabling the form of Cu to significantly influence the oxygen reaction rate in wine.


Assuntos
Cobre/química , Oxigênio/química , Sulfetos/química , Vinho/análise , Estrutura Molecular , Potenciometria
2.
Chem Commun (Camb) ; 56(13): 1968-1971, 2020 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-31957765

RESUMO

Highly water-soluble cyanocobalamin (also known as vitamin B12) is the most structurally macrocyclic complex comprising cobalt in the center of a corrin ring. Interestingly, it acts as a robust electrocatalyst in water oxidation at ∼0.58 V overpotential with a faradaic efficiency of 97.50% under neutral buffered conditions. The catalyst is impressively stable even after long-term bulk electrolysis, and homogeneous in nature, as established by a series of experiments and characterization techniques.


Assuntos
Vitamina B 12/química , Água/química , Catálise , Cobalto/química , Conformação Molecular , Oxirredução , Potenciometria
3.
Chemosphere ; 246: 125718, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31918082

RESUMO

The presence and mobilization of toxic metal cations represents under many aspects a current and important problem in the environmental field. In this research, as cation lead (II) ion was studied. The formation of complexes between glutathione and lead (II) was studied at 25 °C and in 1.00 M NaCl as ionic medium by means of measurements of electromotive force (e.m.f.) of cells containing glass and lead amalgam electrodes. In the same experimental conditions, the protonation constants of glutathione were determined potentiometrically, using a cell containing the glass electrode. In the same experimental conditions, by considering glutathione (GSH) completely deprotonated, four protonation constants were determined. Potentiometric data could be explained by assuming the formation of 1:1 complexes between GSH and Pb2+ and with the participation of hydrogen ions. The stability constants of the assumed complexes were determined. The 1:1 ratio between GSH and lead (II) was confirmed by spectrophotometric investigations. Measurements by Infrared Rays (IR) and protonic Nuclear Magnetic Resonance (1H NMR) provide information on the structure of the found complexes.


Assuntos
Glutationa/metabolismo , Chumbo/metabolismo , Ligantes , Cátions , Glutationa/química , Concentração de Íons de Hidrogênio , Chumbo/química , Espectroscopia de Ressonância Magnética , Potenciometria , Prótons , Espectrofotometria
4.
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
5.
Food Chem ; 309: 125789, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31704073

RESUMO

In this study, the development of an electroanalytical assay based on square wave voltammetry technique for determining sesamol (Ses) in sesame oil samples is described. The influence of various factors such as pH of the supporting electrolyte, its composition, and SW (square wave) parameters was studied. Linearity of the peak current depended on the concentration of Ses in the range from 3.0 to 140.0 µmol L-1 with a limit of detection of 0.71 µmol L-1. Furthermore, the cyclic voltammetric behavior of Ses and the effects of scan rate and pH on the peak current and peak potential of Ses were determined. Moreover, the electrode process was found to be diffusion-controlled. The proposed methodology was successfully applied for determining Ses in commercial sesame oil samples. The obtained results were in good agreement with the results from the HPLC-UV reference method.


Assuntos
Benzodioxóis/análise , Fenóis/análise , Potenciometria , Óleo de Gergelim/química , Carbono/química , Eletrodos , Eletrólitos/química , Concentração de Íons de Hidrogênio , Limite de Detecção
6.
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
7.
Food Chem ; 311: 126013, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31855768

RESUMO

Cost effective, simple and accurate two voltammetric methods for determination of boron in hazelnut, peanut, almond, raisin, prune and date samples were described. Metal nanoparticles-carbon nanotube modified glassy carbon electrode (MNP/CNT/GCE, M = Au or Cu) and poly xylenol orange modified pencil graphite electrode (p-XO/PGE) were used as working electrodes. The oxidation of alizarin red s (ARS) in the boron-ARS complex at MNP/CNT/GCE and the oxidation of tiron in the B-tiron complex at p-XO/PGE were monitored as response. The limit of determination values (based on visual evaluation) for CuNP/CNT/GCE, AuNP/CNT/GCE and p-XO/PGE were calculated as 100 µg/L, 125 µg/L and 80 µg/L, respectively. The results were compared with the results obtained by inductively coupled plasma mass spectrometric method and no significant difference between the results was observed. The accuracy experiments of the methods and uncertainty calculations were also performed using a certified reference material (UME CRM 1202 Elements in Hazelnut).


Assuntos
Boro/análise , Frutas/química , Nozes/química , Potenciometria , Antraquinonas/química , Eletrodos , Frutas/metabolismo , Grafite/química , Nanopartículas Metálicas/química , Nanotubos de Carbono/química , Nozes/metabolismo
8.
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
9.
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
10.
Sensors (Basel) ; 19(21)2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31671716

RESUMO

Monitoring the cellular metabolism of bacteria in (bio)fermentation processes is crucial to control and steer them, and to prevent undesired disturbances linked to metabolically inactive microorganisms. In this context, cell-based biosensors can play an important role to improve the quality and increase the yield of such processes. This work describes the simultaneous analysis of the metabolic behavior of three different types of bacteria by means of a differential light-addressable potentiometric sensor (LAPS) set-up. The study includes Lactobacillus brevis, Corynebacterium glutamicum, and Escherichia coli, which are often applied in fermentation processes in bioreactors. Differential measurements were carried out to compensate undesirable influences such as sensor signal drift, and pH value variation during the measurements. Furthermore, calibration curves of the cellular metabolism were established as a function of the glucose concentration or cell number variation with all three model microorganisms. In this context, simultaneous (bio)sensing with the multi-organism LAPS-based set-up can open new possibilities for a cost-effective, rapid detection of the extracellular acidification of bacteria on a single sensor chip. It can be applied to evaluate the metabolic response of bacteria populations in a (bio)fermentation process, for instance, in the biogas fermentation process.


Assuntos
Bactérias/metabolismo , Técnicas Biossensoriais , Luz , Potenciometria , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Calibragem , Contagem de Colônia Microbiana , Eletrodos , Glucose/farmacologia
11.
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
12.
BMC Oral Health ; 19(1): 251, 2019 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-31747894

RESUMO

BACKGROUND: The aim of this study was to compare free fluoride concentration and total fluoride concentration in mouthwashes. METHODS: Fluorine-containing mouthwashes from various companies and manufacturers (Colgate Total Plax Classic Mint®, Colgate-Palmolive, New York, USA; Colgate Total Plax Gentle Mint®, Colgate-Palmolive, New York, USA; Colgate Total Plax Fresh Mint®, Colgate-Palmolive, New York, USA; Oral B Advantage®, Procter&Gamble, Cincinnati, USA; Reach Fresh Mint®, Johnson&Johnson, New Brunswick, USA; Foramen®, Laboratorios Foramen, Guarnizo, Spain; Lacalut Sensitive®, Dr. THEISS, Homburg, Germany; Sensodyne®, GlaxoSmithKline, London, UK; Vesna F®, Vita, Saint Petersburg, Russia; Lacalut Fresh®, Dr. THEISS, Homburg, Germany) were selected as study objects. Fluoride measurements were carried out using the fluoride selective electrode. RESULTS: Free fluoride:total fluoride ratio was more than 80% for six samples (Colgate Total Plax Gentle Mint® - 88%, Colgate Total Plax Fresh Mint® - 99%, Oral B Advantage® - 92%, Reach Fresh Mint® - 92 and 89% for the mouthwash of another batch, Lacalut Sensitive® - 94%) and less than 63% for three samples (Colgate Total Plax Classic Mint® - 56%, Foramen® - 62%, Vesna F® - 61%). Two samples had more than 70% and less than 80% of unbound fluoride, respectively (Sensodyne® - 77%, another batch of Oral B Advantage® mouthwash - 74%). Rinse containing sodium monofluorophosphate (Na2PO3F) (Vesna F®) had more than 50% of free fluoride, while the rinse containing amine fluoride (AmF) (Lacalut Sensitive®) had 94%. The difference in the free fluoride:total fluoride ratio can be explained by binding of fluoride ions by components contained in mouthwashes, such as coloring agents and polymeric compounds. The lowest concentration of free fluoride ions (0.000093 mol/L) was observed for aluminum fluoride (AlF3) rinse (Lacalut Fresh®), while the total fluoride amount was not determined due to possible generation of strong fluoride complexes. This implies that fluoride ions will not be uptaken by tooth tissue and may even be washed away from it, compromising the efficacy of mouthwashes. CONCLUSIONS: The differences in free fluoride: total fluoride ratio between analyzed mouthwashes reveal a need to develop a method for evaluation of free fluorides in mouthwashes for proper updating of national and international guidelines.


Assuntos
Fluoretos/análise , Eletrodos Íon-Seletivos , Antissépticos Bucais/química , Potenciometria , Humanos
13.
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
14.
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
15.
Molecules ; 24(18)2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31547345

RESUMO

Three 1,4,7,10-tetraazacyclododecane-based ligands disubstituted in 1,4-positions with phosphonic acid, phosphonate monoethyl-ester, and H-phosphinic acid pendant arms, 1,4-H4do2p, 1,4-H2do2pOEt, and 1,4-H2Bn2do2pH, were synthesized and their coordination to selected metal ions, Mg(II), Ca(II), Mn(II), Zn(II), Cu(II), Eu(III), Gd(III), and Tb(III), was investigated. The solid-state structure of the phosphonate ligand, 1,4-H4do2p, was determined by single-crystal X-ray diffraction. Protonation constants of the ligands and stability constants of their complexes were obtained by potentiometry, and their values are comparable to those of previously studied analogous 1,7-disubstitued cyclen derivatives. The Gd(III) complex of 1,4-H4do2p is ~1 order of magnitude more stable than the Gd(III) complex of the 1,7-analogue, probably due to the disubstituted ethylenediamine-like structural motif in 1,4-H4do2p enabling more efficient wrapping of the metal ion. Stability of Gd(III)-1,4-H2do2pOEt and Gd(III)-H2Bn2do2pH complexes is low and the constants cannot be determined due to precipitation of the metal hydroxide. Protonations of the Cu(II), Zn(II), and Gd(III) complexes probably takes place on the coordinated phosphonate groups. Complexes of Mn(II) and alkali-earth metal ions are significantly less stable and are not formed in acidic solutions. Potential presence of water molecule(s) in the coordination spheres of the Mn(II) and Ln(III) complexes was studied by variable-temperature NMR experiments. The Mn(II) complexes of the ligands are not hydrated. The Gd(III)-1,4-H4do2p complex undergoes hydration equilibrium between mono- and bis-hydrated species. Presence of two-species equilibrium was confirmed by UV-Vis spectroscopy of the Eu(III)-1,4-H4do2p complex and hydration states were also determined by luminescence measurements of the Eu(III)/Tb(III)-1,4-H4do2p complexes.


Assuntos
Complexos de Coordenação/química , Gadolínio/química , Compostos Heterocíclicos/química , Organofosfonatos/química , Meios de Contraste , Complexos de Coordenação/síntese química , Cristalografia por Raios X , Európio/química , Ligantes , Espectroscopia de Ressonância Magnética , Manganês/química , Ácidos Fosfínicos/química , Potenciometria , Espectrofotometria Ultravioleta , Temperatura
16.
Molecules ; 24(18)2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31505808

RESUMO

A rapid and accurate determination method for total phenolic content is of great importance for controlling the quality of wine samples. A promising potentiometric detection approach, based on permanganate ion fluxes across ion-selective electrode membranes, is fabricated for measuring the total phenolic content of wine. The results show that the presence of phenols, such as gallic acid, leads to a potential increase for the potentiometric sensor. Additionally, the present sensor exhibits a linear potential response with the concentration range from 0.05 to 3.0 g/L with a detection limit of 6.6 mg/L calculated using gallic acid. These sensors also exhibit a fast response time, an acceptable reproducibility and long-term stability. These results indicate that the proposed potentiometric sensor can be a promising and reliable tool for the rapid determination of total phenolic content in wine samples.


Assuntos
Compostos de Manganês/química , Óxidos/química , Fenóis/isolamento & purificação , Potenciometria , Vinho/análise , Humanos , Íons/química , Fenóis/química
17.
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
18.
PLoS One ; 14(7): e0219299, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31276475

RESUMO

Acute moderate to severe gastroenteritis is traditionally associated with hypernatremia but recent observations suggest that hypernatremia is currently less common than hyponatremia. The latter has sometimes been documented also in children with acute community-acquired diseases, such as bronchiolitis and pyelonephritis. We investigated the prevalence of dysnatremia in children with acute moderate severe gastroenteritis, bronchiolitis and pyelonephritis. This prospective observational study included 400 consecutive previously healthy infants ≥4 weeks to ≤24 months of age (232 males and 168 females): 160 with gastroenteritis and relevant dehydration, 160 with moderate-severe bronchiolitis and 80 with pyelonephritis admitted to our emergency department between 2009 and 2017. Circulating sodium was determined by means of direct potentiometry. For analysis, the Kruskal-Wallis test and the Fisher's exact test were used. Hyponatremia was found in 214 of the 400 patients. It was common in gastroenteritis (43%) and significantly more frequent in bronchiolitis (57%) and pyelonephritis (68%). Patients with hyponatremia were significantly younger than those without hyponatremia (3.9 [1.6-13] versus 7.5 [3.4-14] months). The gender ratio was similar in children with and without hyponatremia. Hyponatremia was associated with further metabolic abnormalities (hypokalemia, hyperkalemia, metabolic acidosis or metabolic alkalosis) in gastroenteritis (71%) and pyelonephritis (54%), and always isolated in bronchiolitis. In conclusion, hyponatremia is common at presentation among previously healthy infants with gastroenteritis, bronchiolitis or pyelonephritis. These data have relevant consequences for the nutrition and rehydration management in these conditions.


Assuntos
Infecções Comunitárias Adquiridas/metabolismo , Hiponatremia/epidemiologia , Doença Aguda , Bronquiolite/complicações , Infecções Comunitárias Adquiridas/complicações , Infecções Comunitárias Adquiridas/epidemiologia , Feminino , Gastroenterite/complicações , Hospitalização , Humanos , Hipernatremia/epidemiologia , Hipernatremia/metabolismo , Hiponatremia/complicações , Hiponatremia/metabolismo , Lactente , Recém-Nascido , Masculino , Potenciometria , Prevalência , Estudos Prospectivos , Pielonefrite/complicações , Sódio/sangue , Sódio/metabolismo
19.
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
20.
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
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