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1.
Phys Chem Chem Phys ; 22(14): 7537-7545, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32219231

RESUMO

Understanding how electrons and protons move in a coupled manner and affect one another is important to the design of proton-electron conductors and achieving biological transport in synthetic materials. In this study, a new methodology is proposed that allows for the quantification of the degree of coupling between electrons and protons in tyrosine-rich peptides and metal oxide hybrid films at room temperature under a voltage bias. This approach is developed according to the Onsager principle, which has been thoroughly established for the investigation of mixed ion-electron conductors with electron and oxide ion vacancies as carriers at high temperatures. Herein, a new device platform using electron-blocking electrodes provides a new strategy to investigate the coupling of protons and electrons in bulk materials beyond the molecular level investigation of coupled proton and electron transfer. Two Onsager transport parameters, αi* and σe', are obtained from the device, and the results of these transport parameters demonstrate that the coupled transport of electrons and protons inside the hybrid film plays an important role in the macroscopic-scale conduction. The results suggest that an average of one electron is dragged by one proton in the absence of a direct driving force for electron movement ∇ηe.


Assuntos
Técnicas de Química Analítica/instrumentação , Transporte de Elétrons/fisiologia , Elétrons , Compostos de Manganês/química , Óxidos/química , Peptídeos/química , Prótons , Transporte Biológico/fisiologia
2.
Artigo em Inglês | MEDLINE | ID: mdl-32065955

RESUMO

Developing dissolution testing methods to measure the nicotine release profiles from smokeless tobacco products is valuable for product assessment and product-to-product comparisons. In this work, we developed a robust dissolution method to study the in vitro release of nicotine from smokeless tobacco products using the U.S. Pharmacopeia flow-through cell dissolution apparatus 4 (USP-4). We further developed and validated a sensitive Ultra Performance Liquid Chromatography coupled to Photodiode Array detector (UPLC-PDA) method for the accurate quantitation of the released nicotine into artificial saliva, which is our selected dissolution medium. We have successfully shown the applicability of the validated method by investigating the release profiles of nicotine from various commercial and CORESTA reference smokeless tobacco products [CRP 1.1 (Swedish-style snus pouch), CRP 2.1 (American-style loose moist snuff), CRP 4 (loose-leaf chewing tobacco) and CRP 4.1 (chopped loose-leaf chewing tobacco)]. Nicotine release profiles were analyzed by calculating the difference factor (f1) and similarity factor (f2) by adopting a methodology referenced in the Guidance for Industry from FDA's Center for Drug Evaluation and Research (CDER) and by fitting the release profile curves using a first order kinetic model. Nicotine release was found to be dependent on the form and cut of the smokeless tobacco products, with a slower release observed for snus and loose-leaf, compared to chopped and loose moist snuff smokeless tobacco. This dissolution methodology can be extended to measure and compare release of other constituents from smokeless tobacco products and has the potential for method standardization.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Nicotina/análise , Tabaco sem Fumaça/análise , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Desenho de Equipamento , Humanos , Limite de Detecção , Modelos Lineares , Modelos Biológicos , Nicotina/farmacocinética , Reprodutibilidade dos Testes , Saliva/química
3.
J Chromatogr A ; 1616: 460774, 2020 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-31937408

RESUMO

Bananas and plantains (Musa spp.) are used as nutritious foods, and at the same time, are a source of phytoconstituents for the pharmaceutical industry. As biological activities of especially the pulp and peel of Musa spp. have been documented, this study investigated the variation in the secondary metabolite profiles of the leaves from field, in vitro-grown and acclimatized accessions. The genetic fidelity of the diverse accessions was assessed using diversity array technology sequencing. It showed that the in vitro-grown accessions were true-to-type with the field samples. The antioxidant and anticholinesterase activities of the samples from different culture systems (field and in vitro) were evaluated by UV-spectrophotometry and compared to high-performance thin-layer chromatography-effect-directed analysis (HPTLC-EDA). The latter was applied for the first time for effect-directed profiling of the polar and medium polar sample components via different biochemical and biological assays. Compound zones showed acetyl-/butylrylcholinesterase inhibition (zones 1-4), α-/ß-glucosidase inhibition (zones 1 and 2) as well as antioxidative (zones 1-3) and antimicrobial (zone 4) activities. Structures were preliminary assigned by HPTLC-HRMS. The HPTLC was effective for bioactivity-guided characterization of the bioactive constituents in Musa spp. accessions. Accumulation of useful metabolites, especially compounds with antioxidant and anticholinesterase properties, was higher in samples from in vitro system. This validated the use of plant tissue culturing as an alternative method for large scale production of plant material and supply of bioactive constituents.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia em Camada Delgada , Espectrometria de Massas , Musa/química , Anti-Infecciosos/isolamento & purificação , Antioxidantes/química , Antioxidantes/isolamento & purificação , Técnicas de Química Analítica/instrumentação , Inibidores da Colinesterase/isolamento & purificação , Inibidores de Glicosídeo Hidrolases/isolamento & purificação , Musa/crescimento & desenvolvimento
4.
J Chromatogr A ; 1614: 460728, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31785896

RESUMO

Triazine rings-containing porous aromatic framework (PAF-56p) was synthesized through a Friedel-Crafts reaction and investigated as a coating for the stir bar sorptive extraction (SBSE) of interest triazines. The triazine rings and conjugated groups in PAF-56p could interact with triazine rings-containing herbicides by hydrophobic and π-π interactions. The PAF-56p coated stir bar showed superior extraction performance over commercial PDMS and EG coated stir bar in terms of extraction efficiency and dynamics towards six triazine herbicides with different polarity. Based on it, a method by combining PAF-56p-SBSE with high performance liquid chromatography (HPLC)-diode array detector (DAD) was established for the analysis of six target triazine herbicides, including simazine, atrazine, ametryn, prometon, prometryne and prebane. The affecting factors of SBSE were investigated by single-factor test. Under the optimized conditions, the limits of detection of the proposed method were ranged from 0.037 to 0.089 µg/L with the linear range within 0.1-200 µg/L for six triazine herbicides. High enrichment factors (EFs) of 61.8-89.5-fold (theoretical EF is 100-fold) were achieved. The developed PAF-56p-SBSE-HPLC-DAD method was successfully applied for trace triazine herbicides analysis in maize and maize leaf samples, with recoveries in the range of 86.5-115% and 85.1-114% for spiked maize and maize leaf samples, respectively.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão , Herbicidas/análise , Triazinas/análise , Zea mays/química , Técnicas de Química Analítica/instrumentação , Herbicidas/isolamento & purificação , Limite de Detecção , Porosidade , Reprodutibilidade dos Testes , Triazinas/isolamento & purificação
5.
J Chromatogr A ; 1614: 460735, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31791591

RESUMO

Two high throughput steady-state methods of counter-current chromatography separations: conventional (SS CCC) and closed-loop recycling (SS CLR CCC) are proposed, evaluated and compared. The methods are based on the application of semi-continuous sample loading technique: the CCC setup includes two mobile phase tanks - one with the pure mobile phase and the second - with the sample solution in the mobile phase. The mobile phase pump is periodically switching from one tank to another. The sample solution is continuously loaded into the CCC column over a constant time with the constant volumetric rate equal to the flow rate of the pure mobile phase. Analytical expressions are developed to describe the SS CCC and SS CLR CCC separations with semi-continuous sample loading. Examples of separation of binary and multicomponent mixtures are discussed. The SS CLR CCC has been shown to provide a multiple increase in the performance and effectiveness of CCC devices. Several examples of simulation of SS CLR CCC separation with semi-continuous sample loading are presented in "Mathcad" program. For the experimental verification of the theory, the separation of the binary mixture caffeine/ coumarin was studied. The biphasic solvent system hexane/isopropanol/water (1:1:1), was used. The comparison of experimental and simulated separations demonstrated a reasonable agreement between theory and experiment.


Assuntos
Técnicas de Química Analítica/métodos , Modelos Químicos , Cafeína/isolamento & purificação , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/normas , Cumarínicos/isolamento & purificação , Hexanos/química , Solventes/química , Água/química
6.
J Chromatogr A ; 1616: 460781, 2020 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-31858997

RESUMO

A facile strategy for highly efficient fabrication of chiral monolithic column was carried out by the simple "one-pot" hydroxymethyl polycondensation of native ß-cyclodextrin (ß-CD) and urea-formaldehyde (UF). In-situ rapid substitution of native ß-CD and efficient polycondensation of ß-CD products and UF oligomers was proposed and fulfilled in one pot. The feasibility, mechanism and key parameters of polycondensation reaction were discussed. The data on crosslinking polycondensation and reaction kinetics were further evaluated. Characteristics including the morphologies, permeability and structure stability of the resultant monolithic columns were also studied. Under the optimal conditions, the "one-pot" hydroxymethyl polycondensation was accomplished in an aqueous solution within only 10 mins. Satisfactory stability and repeatability were gained, and good enantioseparation of eight model enantiomers was successfully achieved with the resultant ß-CD-based monolith. It was simple and highly efficient, and the organic solvents, special CD derivatives and tediously long-time polymerization reaction were successfully avoided, which might light a new access to rapid preparation of CD-chiral monolith for high-performance enantioseparation.


Assuntos
Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Cromatografia Líquida/instrumentação , beta-Ciclodextrinas/química , Permeabilidade , Polimerização , Estereoisomerismo
7.
Nature ; 574(7777): 228-232, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31597972

RESUMO

Microfluidic systems can deliver portable point-of-care diagnostics without the need for external equipment or specialist operators, by integrating all reagents and manipulations required for a particular assay in one device1. A key approach is to deposit picogram quantities of dried reagents in microchannels with micrometre precision using specialized inkjet plotters2-5. This means that reagents can be stored for long periods of time and reconstituted spontaneously when adding a liquid sample. But it is challenging to carry out complex operations using multiple reagents, because shear flow enhances their dispersion and they tend to accumulate at moving liquid fronts, resulting in poor spatiotemporal control over the concentration profile of the reconstituted reagents6. One solution is to limit the rate of release of reagents into the liquid7-10. However, this requires the fine-tuning of different reagents, conditions and targeted operations, and cannot readily produce the complex, time-dependent multireagent concentration pulses required for sophisticated on-chip assays. Here we report and characterize a capillary flow phenomenon that we term self-coalescence, which is seen when a confined liquid with a stretched air-liquid interface is forced to 'zip' back onto itself in a microfluidic channel, thereby allowing reagent reconstitution with minimal dispersion. We provide a comprehensive framework that captures the physical underpinning of this effect. We also fabricate scalable, compact and passive microfluidic structures-'self-coalescence modules', or SCMs-that exploit and control this phenomenon in order to dissolve dried reagent deposits in aqueous solutions with precise spatiotemporal control. We show that SCMs can reconstitute multiple reagents so that they either undergo local reactions or are sequentially delivered in a flow of liquid. SCMs are easily fabricated in different materials, readily configured to enable different reagent manipulations, and readily combined with other microfluidic technologies, so should prove useful for assays, diagnostics, high-throughput screening and other technologies requiring efficient preparation and manipulation of small volumes of complex solutions.


Assuntos
Indicadores e Reagentes/análise , Microfluídica/métodos , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Testes Diagnósticos de Rotina , Ensaios Enzimáticos/instrumentação , Ensaios Enzimáticos/métodos , Fluorometria , Glucosefosfato Desidrogenase/análise , Glucosefosfato Desidrogenase/metabolismo , Papillomavirus Humano 16/genética , Papillomavirus Humano 16/isolamento & purificação , Papillomavirus Humano 18/genética , Papillomavirus Humano 18/isolamento & purificação , Humanos , Microfluídica/instrumentação , Técnicas de Amplificação de Ácido Nucleico/instrumentação , Técnicas de Amplificação de Ácido Nucleico/métodos
8.
Ultrason Sonochem ; 59: 104734, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31479886

RESUMO

Currently near-infrared (NIR) luminescence of lanthanide ions has received great attention because of their unique emissions in the near-infrared region (800-1700 nm). These NIR luminescent materials behave excellent applications in many fields such as sensors and probes in optical amplification, laser systems, biological systems and organic light-emitting diodes. In this work, two new near-infrared (NIR) emission three-dimensional (3D) YbIII and NdIII cluster-based coordination materials, namely {[Yb2(L)2(DMF)(H2O)4]·(DMF)2 (H2O)}n (NIR-MOF 1) and [Nd(L)(DMF)2]n (NIR-MOF 2) (H3L = terphenyl-3,4″,5-tricarboxylic acid) have been synthesized through the facile sono-chemical preparation methods. Both the near-infrared materials 1 and 2 have been characterized by single crystal X-ray diffraction, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Further the mixed-lanthanide near-infrared emission material Nd0.35Yb0.65L (NIR-MOF 3) can also be prepared under the sono-chemical conditions. NIR-MOF 3 can be successfully applied as the ratiometric NIR-MOF-based thermometer, which should origin from the emission intensity ratio between Yb3+ (976 nm) and Nd3+ (1056 nm) in the temperature range of 308-348 K. Besides these, the micro-morphologies of NIR-MOF 1 can be deliberately tuned through different sono-chemical reaction factors (reaction time, reaction temperature and sono-chemical powers). These tuned nano-sized materials NIR-MOF 1 (100 W, 80 min) can be utilized as the fluorescent sensing material to distinguish furazolidone and sulfasalazine from other antibiotics. At the same time, NIR-MOF 2 can be applied as the first example of MOFs-based sensors for discriminating l-arginine from other amino acids through the "turn-on" mode in the near-infrared emission region.


Assuntos
Antibacterianos/análise , Arginina/análise , Técnicas de Química Analítica/instrumentação , Raios Infravermelhos , Neodímio/química , Ondas Ultrassônicas , Itérbio/química , Antibacterianos/química , Arginina/química , Furazolidona/análise , Furazolidona/química , Cinética , Limite de Detecção , Modelos Moleculares , Conformação Molecular , Compostos Organometálicos/química , Solventes/química , Sulfassalazina/análise , Sulfassalazina/química , Temperatura
9.
Anal Bioanal Chem ; 411(25): 6561-6573, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31444532

RESUMO

Self-propelled micromotors are micro- and nanoscale devices that move autonomously in solution by converting a specific stimulus into mechanical work. The broad scope of operations and applications along with the ultra-small dimensions have opened new possibilities to solve complex analytical challenges. Herein we give a critical overview of early developments and future prospects of such tiny moving objects for different analytical sensing and biosensing strategies. From early electrophoretic propelled nanomotors, which were limited to low viscous media, to bubble-propelled micromotors, the field has evolved into sophisticated all-in-one analytical systems with built-in sensing capabilities. Current progress for in vivo biosensing and integration into analytical instrumentation towards fully functional devices will be also covered. We hope that this review provides the reader with some general knowledge and future prospects of self-propelled micromachines as a new paradigm in analytical chemistry. Graphical abstract.


Assuntos
Técnicas Biossensoriais/métodos , Técnicas de Química Analítica/métodos , Microtecnologia/métodos , Animais , Técnicas Biossensoriais/instrumentação , Técnicas de Química Analítica/instrumentação , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Desenho de Equipamento , Humanos , Microtecnologia/instrumentação , Nanoestruturas/química , Nanotecnologia/instrumentação , Nanotecnologia/métodos
10.
PLoS One ; 14(8): e0220176, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31461460

RESUMO

Here we present novel method development and instruction in the construction and use of Field Portable Gas Analyzers study of belowground aerobic respiration dynamics of deep soil systems. Our Field-Portable Gas Analysis (FPGA) platform has been developed at the Calhoun Critical Zone Observatory (CCZO) for the measurement and monitoring of soil O2 and CO2 in a variety of ecosystems around the world. The FPGA platform presented here is cost-effective, lightweight, compact, and reliable for monitoring dynamic soil gasses in-situ in the field. The FPGA platform integrates off-the-shelf components for non-dispersive infrared (NDIR) CO2 measurement and electro-chemical O2 measurement via flow-through soil gas analyses. More than 2000 soil gas measurements have been made to date using these devices over 4 years of observations. Measurement accuracy of FPGAs is consistently high as validated via conventional bench-top gas chromatography. Further, time series representations of paired CO2 and O2 measurement under hardwood forests at the CCZO demonstrate the ability to observe and track seasonal and climatic patterns belowground with this FPGA platform. Lastly, the ability to analyze the apparent respiratory quotient, the ratio of apparent CO2 accumulation divided by apparent O2 consumption relative to the aboveground atmosphere, indicates a high degree of nuanced analyses are made possible with tools like FPGAs. In sum, the accuracy and reliability of the FPGA platform for soil gas monitoring allows for low-cost temporally extensive and spatially expansive field studies of deep soil respiration.


Assuntos
Dióxido de Carbono/análise , Técnicas de Química Analítica/instrumentação , Oxigênio/análise , Solo/química , Atmosfera/química , Fatores de Tempo
11.
Analyst ; 144(16): 4848-4857, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31294736

RESUMO

Fibrinogen is a blood protein that is essential for clotting. It is converted into the polymer fibrin by the blood enzymes thrombin and factor XIIIa. Fibrinogen is one of the first proteins to be depleted in heavily bleeding patients. Patients with early hypofibrinogenemia need urgent fibrinogen replenishment to prevent the onset of haemorrhage and death. However, currently there is no rapid, sensitive, cheap and easy-to-use fibrinogen assay that can detect fibrinogen concentrations. In this study, we have developed a new paper-based diagnostic to quantify the fibrinogen concentration in blood at room temperature. This diagnostic is a 2-step process: first, plasma is added onto thrombin-treated paper strips where fibrinogen is converted to fibrin; then the strips are placed into an aqueous dye bath where elution occurs. The test operates by measuring the change in hydrophobicity, which increases with fibrinogen concentration under otherwise constant conditions. The diagnostic can precisely measure fibrinogen concentration within the range of 0-2 g L-1, which is ideal for the clinical diagnosis of hypofibrinogenemia. Furthermore, testing needs only 12 µL of plasma, 60 mU of thrombin and 7.5 minutes of testing. This diagnostic has the potential to revolutionise point of care testing and save many lives.


Assuntos
Técnicas de Química Analítica/métodos , Fibrinogênio/análise , Papel , Afibrinogenemia/diagnóstico , Animais , Compostos Azo/química , Bovinos , Técnicas de Química Analítica/instrumentação , Corantes/química , Fator XIIIa/química , Fibrina/química , Fibrinogênio/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Testes Imediatos , Soroalbumina Bovina/química , Trombina/química , Viscosidade
12.
Talanta ; 204: 576-585, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357337

RESUMO

The aim of this study was to develop and validate a microtiter macro lens-coupled smartphone (MCS) assay for the quantitation of the total saponins in quinoa based on foam measurement. The 96-well micro plate with a black bottom and an inclination angle = 12.102° of macro lens-coupled smartphone allows to acquire images with a high resolution. The foam stability, a critical aspect for the MCS assay, was significantly improved by the inclusion of a chelating agent (EDTA 50 mmol L-1) and bovine serum albumin (0.5 mg mL-1). The MCS assay was linear within the range of 9.039-180.773 × 10-4 mg mL-1 of saponin (R2 = 0.9929), using the integrated density/area as a foam measurement (Y) and the logarithm of saponin concentration (X) (Y = 372.1 + 104.2LogX). The MCS assay was 50-folds more sensitive than afrosimetric assay -AA- with LOD = 3.168 × 10-4 mg mL-1 and LOQ = 4.784 × 10-4 mg mL-1. MCS assay was more reproducible (relative standard deviation (RSD) = 0.632-9.646%) than AA (RSD = 3.44-44.04%). The correlation analysis, Bland-Altman analysis and Passing-Bablok regression showed good agreement between total saponin content in quinoa as measured by the MCS assay and AA. Based on the green analytical procedure index, MCS assay can be considered as a green procedure.


Assuntos
Técnicas de Química Analítica/métodos , Chenopodium quinoa/química , Química Verde/métodos , Saponinas/análise , Smartphone , Animais , Bovinos , Técnicas de Química Analítica/instrumentação , Ácido Edético/química , Química Verde/instrumentação , Limite de Detecção , Reprodutibilidade dos Testes , Sementes/química , Soroalbumina Bovina/química
13.
J Chromatogr A ; 1605: 360347, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31296333

RESUMO

In the present proof-of-concept study, we demonstrate that retention time, selectivity and resolution can be increased in asymmetrical flow field-flow fractionation (AF4) by introducing microstructured ultrafiltration membranes. Evenly spaced micron-sized grooves, that are placed perpendicular to the channel flow on the accumulation wall of a field-flow fractionation system, cause a decrease in the zone velocity which is stronger for larger solutes. This has been demonstrated in thermal field-flow fractionation, and we prove that this is also the case in AF4. We examine the hypothesis theoretically and experimentally, by both computational and physical experiments. By means of moment analysis, we derive theoretically a set of equations which, under certain conditions, describe the mass transport and relate retention time, selectivity and plate height to the dimensions of the grooves. Physical experiments are carried out using microstructured polyethersulfone membranes fabricated by hot embossing, and the experimental results are compared with computational fluid dynamics experiments.


Assuntos
Técnicas de Química Analítica/instrumentação , Fracionamento por Campo e Fluxo/instrumentação , Hidrodinâmica , Polímeros/química , Sulfonas/química , Ultrafiltração
14.
Anal Chim Acta ; 1077: 14-29, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31307702

RESUMO

Electronic nose (enose, EN) and electronic tongue (etongue, ET) have been designed to simulate human senses of smell and taste in the best possible way. The signals acquired from a sensor array, combined with suitable data analysis system, are the basis for holistic analysis of samples. The efficiency of these instruments, regarding classification, discrimination, detection, monitoring and analytics of samples in different types of matrices, is utilized in many fields of science and industry, offering numerous practical applications. Popularity of both types of devices significantly increased during the last decade, mainly due to improvement of their sensitivity and selectivity. The electronic senses have been employed in pharmaceutical sciences for, among others, formulation development and quality assurance. This paper contains a review of some particular applications of EN and ET based instruments in pharmaceutical industry. In addition, development prospects and a critical summary of the state of art in the field were also surveyed.


Assuntos
Nariz Eletrônico , Preparações Farmacêuticas/análise , Técnicas de Química Analítica/instrumentação , Técnicas de Química Analítica/métodos , Humanos
15.
Methods Mol Biol ; 2027: 61-73, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31309472

RESUMO

The incorporation of organic polymeric materials into chemical sensors and electro-optic devices has the potential to greatly advance these fields. A major challenge to their incorporation is the fabrication of thin films due to their intolerance of thermal deposition methods and solvent compatibility challenges. Here, a method for contact printing of quantum dot (QD) and organic polymer (OP) composites for the production of thin-film chemical sensors is described. The method described here allows for the repeatable, low-cost, and relatively simple production of thin films of QD/OP composites for use in chemical sensor arrays by a dry transfer process of the polymer on an elastomer stamp to the sensor substrate.


Assuntos
Técnicas de Química Analítica/instrumentação , Elastômeros/química , Impressão Tridimensional , Pontos Quânticos/química , Fluorescência , Tamanho da Partícula , Solventes/química , Propriedades de Superfície
16.
J Fluoresc ; 29(3): 797-802, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31175507

RESUMO

A simple pyrene-based "turn-on" chemosensor bearing isonizide namely 3-(pyren-1-yl methylene) pentane-2,4-diyldene di(isonicotinohydrazide) (PMPD) was designed and synthesized for detecting Fe3+and Fe2+ ions in HEPES buffer solution at pH 7.4 (DMSO: H2O (1:9 v/v)) medium. The probe shows conducive selectivity for Fe2+ and Fe3+ ions over the other competitive metal cations. The detection limit was found to be 1.67 µM for Fe3+ and 2.02 µM for Fe2+. The recognition mechanism of PMPD towards Fe3+ and Fe2+ has been examined in detail by absorption, emission, and ESI-MS studies. Moreover, "turn-on" fluorescence behavior of the probe was used to track iron ions in living cells.


Assuntos
Técnicas de Química Analítica/instrumentação , Ferro/análise , Ferro/química , Imagem Óptica/métodos , Pirenos/química , Sobrevivência Celular , Transporte de Elétrons , Corantes Fluorescentes/química , Limite de Detecção
17.
J Chromatogr A ; 1602: 74-82, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31176481

RESUMO

The purpose of this study was to develop a new method for the sampling and analysis of naphthalene (Nap) and phenanthrene (Phe) in air. XAD-2 sorbent was prepared with polyaniline (PANI) to increase its adsorption area. Thus, 22-gauge needles were packed with XAD-2/PANI sorbent for the extraction of Nap and Phe, and sampling of the analytes of interest. The compounds were dynamically sampled from the headspace of the flask in laboratory and then analyzed using a gas chromatography (GC) device equipped with flame ionization detector (FID). The needle trap device (NTD) with the proposed sorbent was more sensitive and accurate than the NIOSH 5515 method. The results showed that the optimal temperature and time for the desorption of the analytes were 350 °C and 8 min, respectively. The analytical parameters such as carryover effect, breakthrough volume, and storage time were examined. The repeatability of the method was determined to be 9.4-13.5% for Nap and 7.1-15.7% for Phe. The limits of detection (LOD) for the analytes were in the range 0.002 - 0.09 ng L-1, and the limits of quantitation (LOQ) were in the range 0.01- 0.23 ng L-1. It was also found that the NTD packed with XAD-2/PANI sorbent was a sensitive and cost-effective method, and offered a high accuracy for the sampling and analysis of PAHs in air.


Assuntos
Poluentes Atmosféricos/análise , Compostos de Anilina/química , Técnicas de Química Analítica/instrumentação , Naftalenos/análise , Fenantrenos/análise , Adsorção , Poluentes Atmosféricos/isolamento & purificação , Cromatografia Gasosa , Ionização de Chama , Limite de Detecção , Agulhas , Hidrocarbonetos Policíclicos Aromáticos/análise , Temperatura
18.
J Fluoresc ; 29(3): 751-756, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31127439

RESUMO

In this work, determination of aspartic acid by N-doped carbon dots (N-CDs) was studied at optimum condition. Characterization and morphology of surface of N-CDs were carried out by FT-IR and HRTEM. N-doped carbon dots size was 10 nm. Quenching was very fast after addition of aspartic acid that is an important property of this sensor. Optimum conditions for pH and excitation wavelength were 8 and 360 nm, respectively. Linear dynamic range and limit of detection for aspartic acid were 0.5-50 µM and 90 nM, respectively. This method was used for aspartic acid determination in human serum and sport supplement powder as real samples. Performance of this sensor was also compared with other fluorescent sensors.


Assuntos
Ácido Aspártico/análise , Carbono/química , Técnicas de Química Analítica/instrumentação , Custos e Análise de Custo , Micro-Ondas , Nitrogênio/química , Esportes , Ácido Aspártico/sangue , Técnicas de Química Analítica/economia , Técnicas de Química Sintética , Humanos , Limite de Detecção , Pontos Quânticos/química , Espectrometria de Fluorescência , Fatores de Tempo
19.
J Fluoresc ; 29(3): 737-749, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31123957

RESUMO

The synthesis and optical studies of salicylate based azo derivatives (DPSAD and IPSAD) are reported. The receptors act as a versatile fluorogenic chemosensor for Zn2+ causing a selective enhancement of fluorescence over other competing cations. The complex formed between receptors and Zn2+ are identified on the basis of absorption and fluorescence titration and further confirmed by ESI-MS. DFT/TD-DFT calculations support the observed optical changes happens only upon complexation with Zn2+ ion. Moreover, receptors are further applied to intracellular sensing and imaging studies. Graphical Abstract Salicylate based azo derivatives (DPSAD and IPSAD) as fluorogenic chemosensor for the detection of Zn2+ ion.


Assuntos
Compostos Azo/química , Técnicas de Química Analítica/instrumentação , Corantes Fluorescentes/química , Imagem Óptica/métodos , Ácido Salicílico/química , Zinco/análise , Zinco/química , Sobrevivência Celular , Teoria da Densidade Funcional , Células HeLa , Humanos , Modelos Moleculares , Conformação Molecular , Espectrometria de Fluorescência
20.
ACS Sens ; 4(5): 1365-1372, 2019 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-31062965

RESUMO

Gas molecules are known to interact with two-dimensional (2D) materials through surface adsorption where the adsorption-induced charge transfer governs the chemiresistive sensing of various gases. Recently, titanium carbide (Ti3C2T x) MXene emerged as a promising sensing channel showing the highest sensitivity among 2D materials and unique gas selectivity. However, unlike conventional 2D materials, MXenes show metallic conductivity and contain interlayer water, implying that gas molecules will likely interact in a more complex way than the typical charge transfer model. Therefore, it is important to understand the role of all factors that may influence gas sensing. Here, we studied the gas-induced interlayer swelling of Ti3C2T x MXene thin films and its influence on gas sensing performance. In situ X-ray diffraction was employed to simultaneously measure dynamic swelling behavior where Ti3C2T x MXene films displayed selective swelling toward ethanol vapor over CO2 gas. Results show that the controlling sodium ion concentration in the interlayers is highly important in tuning the swelling behavior and gas sensing performance. The degree of swelling matched well with the gas response intensity, and the highest gas selectivity toward ethanol vapor was achieved for Ti3C2T x sensing channels treated with 0.3 mM NaOH, which also displayed the largest amount of swelling. Our results demonstrate that controlling the interlayer transport of Ti3C2T x MXene is essential for enhancing the selective sensing of gas molecules.


Assuntos
Técnicas de Química Analítica/instrumentação , Gases/análise , Elementos de Transição/química , Difração de Raios X , Modelos Moleculares , Conformação Molecular
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