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1.
Viruses ; 13(9)2021 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-34578456

RESUMO

The worldwide pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its emergence of variants needs rapid and point-of-care testing methods for a broad diagnosis. The regular RT-qPCR is time-consuming and limited in central laboratories, so a broad and large-scale screening requirement calls for rapid and in situ methods. In this regard, a reverse transcription recombinase-aided amplification (RT-RAA) is proposed here for the rapid and point-of-care detection of SARS-CoV-2. A set of highly conserved primers and probes targeting more than 98% of SARS-CoV-2 strains, including currently circulating variants (four variants of concerns (VOCs) and three variants of interest (VOIs)), was used in this study. With the preferred primers, the RT-RAA assay showed a 100% specificity to SARS-CoV-2 from eight other respiratory RNA viruses. Moreover, the assay here is of a high sensitivity and 0.48 copies/µL can be detected within 25 min at a constant temperature (42 °C), which can be realized on portable equipment. Furthermore, the RT-RAA assay demonstrated its high agreement for the detection of SARS-CoV-2 in clinical specimens compared with RT-qPCR. The rapid, simple and point-of-care RT-RAA method is expected to be an appealing detection tool to detect SARS-CoV-2, including variants, in clinical diagnostic applications.


Assuntos
COVID-19/diagnóstico , COVID-19/virologia , Técnicas de Amplificação de Ácido Nucleico/métodos , Testes Imediatos , SARS-CoV-2/genética , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Técnicas de Amplificação de Ácido Nucleico/normas , Reação em Cadeia da Polimerase em Tempo Real , Sensibilidade e Especificidade
2.
Talanta ; 235: 122747, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34517615

RESUMO

Microchip capillary electrophoresis (MCE) is a powerful technique for rapid separation; however, its acceptance in routine laboratories is still limited. Compromises caused by the efforts for solving different problems, such as reducing its cost of fabrication and ensuring high separation efficiency, undermine the competitiveness of this technology compared to other separation techniques. Contrary to the conventional pursuit of narrow microchannels, this study investigated the suitability of microchips with channels at the sub-millimeter level, targeting the simplification of the overall operation, cost reduction, and robustness improvement. To this effect, we considered the influence of pressurized flow and Joule heating on the separation. The suppression of pressurized flow with viscous solutions was confirmed through a combination of simulations and experimental results, indicating that the buffer viscosity was enough for successful separation. We fabricated channels of 200 µm × 230 µm using computer numerical controlled (CNC) machining and obtained theoretical plate numbers of 4.8 × 105 m-1 and 5.3 × 105 m-1 for fluorescein isothiocyanate (FITC) labeled small molecules and DNA fragments, respectively, with a buffer viscosity of 168 mPa s (0.5 % hydroxypropyl methylcellulose, HPMC). These values are comparable with that of narrow-bore microchips. Furthermore, we did not observe any deleterious effects with low-conductivity buffers. We investigated the rapid and highly sensitive detection of mycoplasma contamination and the real samples of circulating cell-free DNA (cfDNA), which gave a limit of detection (LOD) as low as 2.3 ng mL-1. Owing to the significant reduction in cost, ease of operation, and fast separation capabilities demonstrated in this work, MCE can be a viable alternative to the usual slab gel electrophoresis running in most biological laboratories.


Assuntos
Eletroforese em Microchip , DNA , Eletroforese Capilar , Derivados da Hipromelose , Limite de Detecção
3.
Chem Sci ; 12(11): 4111-4118, 2021 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-34163682

RESUMO

The analysis of single living cells, including intracellular delivery and extraction, is essential for monitoring their dynamic biochemical processes and exploring intracellular heterogeneity. However, owing to the 2D view in bright-field microscopy and optical distortions caused by the cell shape and the variation in the refractive index both inside and around the cells, achieving spatially undistorted imaging for high-precision manipulation within a cell is challenging. Here, an accurate and visual system is developed for single-cell spatial manipulation by correcting the aberration for simultaneous bright-field triple-view imaging. Stereo information from the triple view enables higher spatial resolution that facilitates the precise manipulation of single cells. In the bright field, we resolved the spatial locations of subcellular structures of a single cell suspended in a medium and measured the random spatial rotation angle of the cell with a precision of ±5°. Furthermore, we demonstrated the visual manipulation of a probe to an arbitrary spatial point of a cell with an accuracy of <1 pixel. This novel system is more accurate and less destructive for subcellular content extraction and drug delivery.

4.
J Hazard Mater ; 417: 125986, 2021 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-33990038

RESUMO

Sensitive, convenient and rapid detection devices for toxic Cr(VI) suitable for filed use are required. Smartphone can be used as the detector, but the quality of images taken with a smartphone may depend on the ambient light and the operator. In this work, two types of low-cost and portable smartphone-based devices used for fluorescence spots brightness and size dual-mode detection of Cr(VI) were constructed with the aid of the 3D printing, which avoids the effect of ambient light and maintains a fixed position of the phone camera relative to the samples. Based on the brightness reflected by the blue channel of RGB values of the images of carbon nanodots, a linear relationship between quenching efficiency and concentration of Cr(VI) in a range of 0.2-150 µM with a limit of detection of 0.058 µM was attained, which is comparable to or better than that from fluorescence spectrometers. With the size variation of fluorescence spots, a linear range of 10-350 µM was acquired and it is more intuitive for direct naked-eye estimation of the concentration of Cr(VI). The applicability of the proposed devices for the detection of Cr(VI) was verified with water and soil samples with recoveries ranging in 95.0-108.2%.


Assuntos
Pontos Quânticos , Carbono , Cromo , Smartphone
5.
Talanta ; 228: 122224, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33773729

RESUMO

Carbon nanodots (CNDs) have been widely applied in variety of fields, while some evidences indicate their components may be complicated. In this work, capillary electrophoresis (CE) was used to evaluate the effect of synthetic conditions of fluorescent CNDs prepared through the hydrothermal method using citric acid (CA) and Triaminoguanidinium chloride (TGCl) as the starting materials. The results indicated that the fluorescent components of the products were affected by the ratio of the starting materials, the reaction temperature and reaction time. Under selected conditions, a ratio of TGCl to CA of 1:6, the reaction at 180 °C for 3 h, the product contains more than 4 fluorescent components with similar optical properties. CNDs were used for the determination of Cr(VI) in environmental samples with recoveries ranging in 95.3-107%, and the mechanism was also confirmed.

6.
Mikrochim Acta ; 188(3): 82, 2021 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-33586055

RESUMO

A uniform Schiff base network (SNW) film was synthesized in situ in a controllable way through continuous flow of reactants inside the capillary. The properties and application of the as-prepared capillary was investigated in capillary electrochromatography. The effects of reaction monomer concentration and reaction time on coating thickness were studied by SEM. The results show that the reaction condition has a significant influence on the morphology and thickness of the SNW films. The thickness of the film can be controlled by changing the concentration of reaction solution and reaction time. Capillaries coated under different conditions were employed to separate four nucleotides by capillary electrochromatography, which demonstrated significant variation of migration time, peak order, and separation efficiency. Analytes containing nitrogen heterocycle structures, such as nucleotides, methylimidazole isomers, and ß-lactam antibiotics, were successfully separated with the prepared open-tubular columns. Under the selected separation conditions, theoretical plate number of four nucleotides is in a range 45,237-104,505 plates·m-1, and the resolutions are 1.98-8.07. A resolution of 1.75 is obtained for methylimidazole isomers. The nucleotides in a real sample, chicken essence seasoning, were determined using the prepared capillary column with satisfactory recoveries in the range 95 to 105%.

7.
J Chromatogr A ; 1635: 461729, 2021 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-33250162

RESUMO

Considering pH-dependent fluorescence of curcuminoids, a microemulsion electrokinetic chromatographic (MEEKC) method was developed under acidic conditions for their separation and detection using laser-induced native fluorescence (LINF), so as to solve the analysis of urine metabolism for curcuminoids. The microemulsion composition was optimized by response surface methodology (RSM), and the effects of buffer pH and organic modifiers were systematically investigated. The optimal buffer for the separation of curcuminoids was chosen as follows: 2.8% (v/v) ethyl acetate, 80 mM SDS and 2.8% (v/v) n-butanol to form microemulsion, 28% (v/v) ethanol as organic modifier, and 20 mM phosphoric acid as electrolyte at pH 3.0. Under these conditions, four curcuminoids including curcumin, demethoxy curcumin (DMC), bisdemethoxy curcumin (BDMC) and demethyl curcumin (DEC) could be well separated within 18 min, and the detection limits (LOD, based on S/N=3) were calculated to be 71, 60, 22, and 147 pg mL-1, respectively. Combined with solid-phase extraction (SPE), the developed MEEKC-LINF method has been successfully applied to continuously monitor the curcuminoids and related metabolites in human urine collected from a healthy volunteer after oral administration of curry, testifying that this method has potential for evaluating the pharmacological activity of curcuminoids.


Assuntos
Cromatografia , Diarileptanoides/urina , Urinálise/instrumentação , Urinálise/métodos , Diarileptanoides/isolamento & purificação , Emulsões , Fluorescência , Humanos , Lasers , Extração em Fase Sólida
8.
Molecules ; 25(15)2020 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-32752084

RESUMO

Flavonoids are the main constituents of Goji berries and have good biological and pharmacological activities. The mixed-mode macroporous adsorption resins (MARs) for purification of flavonoids from Goji berries through computer-assisted calculation of the molecular size of flavonoids and the precise matching of MAR physical and chemical properties was firstly developed in the present study. Ten varieties of MARs with suitable molecular dimensions and polarities were used for investigating the adsorption/desorption behaviors of the flavonoids. Both AUKJ-1 and BWKX-1 showed higher separation efficiency than other MARs and then were mixed in different ratios to constitute a mixed-mode macroporous adsorption resin to obtain the optimal adsorption phase. Under optimal conditions, total flavonoid content of purified flavonoid (p-FLA) extract increased from 0.97% to 36.88% after one purification. The p-FLA extract from Goji berries significantly improved the expression of six genes with anti-aging effects and played an important role in aging-related Alzheimer's disease by down-regulating Aß expression.


Assuntos
Peptídeos beta-Amiloides/metabolismo , Flavonoides/química , Lycium/química , Resinas Sintéticas/química , Adsorção , Envelhecimento/efeitos dos fármacos , Peptídeos beta-Amiloides/genética , Animais , Animais Geneticamente Modificados/genética , Animais Geneticamente Modificados/metabolismo , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Cromatografia Líquida de Alta Pressão , Flavonoides/isolamento & purificação , Flavonoides/farmacologia , Expressão Gênica/efeitos dos fármacos , Humanos , Lycium/metabolismo , Extratos Vegetais/química , Porosidade
9.
Electrophoresis ; 41(15): 1273-1279, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32358896

RESUMO

Mutations in the potassium channel genes may be linked to the development of epilepsy and affect the blood potassium levels. Therefore, accurate determination of potassium in the blood will be critical to diagnose the cause of epilepsy. CE is a competent technique for the fast detection of multiple ions, but complicated matrices of a blood sample may cause significant variation of migration times and the peak shape. In this work, a procedure for rapid stabilization of the capillary inner surface through preflushing of a blood sample was employed. The process takes only 40 min for a capillary and then it can be used for more than 2 weeks. No pretreatment of the blood sample or other surface modification of the capillary is needed for the analysis. The RSDs of the migration time and peak area were reduced to 1.5 and 5.1% from 12.6 and 14.5%, respectively. The proposed method has been successfully applied to the determination of the potassium contents in the blood sample of patients with epilepsy at different stages. The recoveries of potassium ions in these blood samples are in a range from 86.5 to 104.5%.


Assuntos
Eletroforese Capilar/métodos , Epilepsia/diagnóstico , Potássio/sangue , Coleta de Amostras Sanguíneas , Humanos , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
10.
Chem Commun (Camb) ; 56(16): 2423-2426, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-31994543

RESUMO

A highly sensitive laser-induced fluorescence detection system with real-time imaging focusing instead of the use of fluorescent reagents were developed for the detection of analytes in nanocapillaries. A cylindrical lens was adopted for the shaping of a laser beam to increase its spatial resolution. The limit of detection with a capillary having a radius of 440 nm was 6.76 yoctomoles (or four molecules) for fluorescein, and 84.5 yoctomoles (or 51 molecules) for FAM-labeled Hsa-miR-17. The designed system exhibited high sensitivity and stability for femtoliters of sample and was hence indicated to be suitable for analyses of single cells.


Assuntos
Fluorescência , Corantes Fluorescentes/química , Lasers , MicroRNAs/análise , Imagem Óptica , Análise de Célula Única , Humanos , Espectrometria de Fluorescência , Fatores de Tempo
11.
ACS Appl Mater Interfaces ; 12(7): 8773-8779, 2020 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-31997635

RESUMO

Electrophoretic separation in short microchannels is a promising way for rapid analysis of biomolecules, but the pressurized laminar flow may compromise the separation efficiency. In this work, through an electric field, instant formation and removal of a solid chitosan/ß-glycerol phosphate (CS/ß-GP) hydrogel within microchannels of microchips were realized. In a typical cross-type microchip, the CS/ß-GP hydrogel was precisely formed in the separation microchannel within 15 s of the application of a voltage of 2000 V. Highly efficient separation of peptides and proteins was achieved, and theoretical plate numbers of 0.6 to 1.5 × 106/m were attained for proteins in 120 s. The used hydrogel could be swiftly removed also with an electric field, and the whole procedure was achieved on a standard microchip electrophoresis device with no extra accessory or special operation required.


Assuntos
Eletroforese em Microchip/métodos , Desenho de Equipamento/instrumentação , Glicerofosfatos/química , Hidrogéis/química , Quitosana/química , Eletricidade , Eletroforese em Microchip/instrumentação , Desenho de Equipamento/métodos , Células HeLa , Humanos , Hidrogéis/síntese química , Proteínas/química
12.
Anal Chem ; 91(24): 15670-15677, 2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31710814

RESUMO

Exploration of simple and universal methods to quantitatively measure nanoparticle (NP)-protein interaction is of great importance. In this work, pulsed streaming potential (SP) measurement has been used to evaluate the interaction between NPs and proteins within microchannels. Graphene oxide (GO) and SiO2 NPs were selected to represent two kinds of NPs. Lysozyme and common blood proteins, including albumin V, γ-globulins, and fibrinogen, were used as model proteins. The linear relationship between the initial adsorption rate (S = dEr/dt) and the concentration of proteins was observed. Combined with the Hill equation, the microscopic dissociation constant (KD) and the Hill coefficient (n) between NPs and proteins were calculated based on the relationship between S and the concentration of each protein. The concentration of free proteins which have not interacted with the NPs in the NPs-protein mixture could also be measured. The influence of pH, conductivity, and ionic strengths of the incubation buffer on the interaction between GO and lysozyme was evaluated based on the constant KD. The interaction intensity between NPs and proteins was defined as charge neutralization efficiency QC, which could be calculated from the value of S. It takes only 150 s to get the whole set of data under the optimized experiment parameters. The measurement solely depends on the surface charge, no intrinsic fluorescence is required for either the NPs or the proteins, and no labeling or immobilization process is involved as well.


Assuntos
Albuminas/metabolismo , Fibrinogênio/metabolismo , Grafite/química , Muramidase/metabolismo , Nanopartículas/química , Dióxido de Silício/química , gama-Globulinas/metabolismo , Adsorção , Albuminas/química , Fibrinogênio/química , Grafite/metabolismo , Humanos , Muramidase/química , Nanopartículas/metabolismo , Concentração Osmolar , Dióxido de Silício/metabolismo , gama-Globulinas/química
13.
J Agric Food Chem ; 67(28): 8053-8060, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31276393

RESUMO

The development of analytical methods for acrylamide formed during food processing is of great significance for food safety, but limited by its inherent characteristics, the analysis of acrylamide is a continuing challenge. In this study, an efficient derivatization strategy for acrylamide based on thiol-ene click reaction with cysteine as derivatization reagent was proposed, and the resulting derivative was then analyzed by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). After systematic investigation including catalyst dosage (0-20 mM), reaction temperature (30-90 °C) and time (1-60 min), and cysteine concentration (0.2-3.6 mM), acrylamide could be efficiently labeled by 2.0 mM cysteine at 70 °C for 10 min using 4 mM n-butylamine as catalyst. Application of 10 mM triethylamine as separation buffer, the labeled acrylamide was analyzed within 2.0 min, and the relative standard deviations of migration time and peak area were less than 0.84% and 5.6%, indicating good precision. The C4D signal of acrylamide derivative showed a good linear relationship with acrylamide concentration in the range of 7-200 µM with the correlation coefficient of 0.9991. The limit of detection and limit of quantification were calculated to be 0.16 µM and 0.52 µM, respectively. Assisted further by the QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample pretreatment, the developed derivatization strategy and subsequent CE-C4D method were successfully applied for the determination of acrylamide in potato products.


Assuntos
Acrilamida/análise , Química Click/métodos , Eletroforese Capilar/métodos , Solanum tuberosum/química , Culinária , Cisteína/química , Temperatura Alta , Limite de Detecção , Tubérculos/química
14.
Talanta ; 203: 83-89, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31202353

RESUMO

An integrated immunodetection platform employing a simple, reusable, centrifugal microchannel array chip and a smartphone as detection unit was developed. The applicability of the platform to the detection of HIV p24 antigen was demonstrated. The microchip was made of polycarbonate and contained 4 × 8 zigzag microchannels. After the monoclonal antibody of HIV p24 was adsorbed onto the channel surfaces, HIV p24 was introduced into the microchannel to react with the antibody. A biotin linked polyclonal antibody was then brought in to react with HIV p24, and SP80 (containing streptavidin and horseradish peroxidase) was introduced to react with the biotin. Finally, a solution containing 3,3',5,5'-tetramethylbenzidine and other reagents was passed through the above channels, horseradish peroxidase catalyzed the oxidation of tetramethylbenzidine (to 3,3',5,5'- tetramethylbenzidine diamine) forming a dark color. The color intensity, indicating HIV p24 antigen quantity, was then photographed via a smartphone, and the color of each microchannel was processed via a computer to determine the HIV p24 antigen concentration. Under the optimized conditions, limits of detection (LODs) of 0.17 ng/ml and 0.11 ng/ml were obtained for p24 antigen in a buffer solution and human serum, respectively. Channel washing/rinsing was implemented via a centrifugal force. An economic portable centrifugal device that could accommodate up to 4 microchips was assembled, and multi-step solution loading and rinsing involved in this sandwich immunoassay were performed conveniently. The microchip could be reused after a simple regeneration process. The low-cost polycarbonate microchip and centrifugal device together with the simple but efficient operation make the method a promising tool for HIV screening in resource limited areas.


Assuntos
Proteína do Núcleo p24 do HIV/análise , Dispositivos Lab-On-A-Chip , Smartphone , Animais , Anticorpos Monoclonais Murinos/imunologia , Armoracia/enzimologia , Centrifugação , Ensaio de Imunoadsorção Enzimática/métodos , Desenho de Equipamento , Reutilização de Equipamento , HIV/química , Proteína do Núcleo p24 do HIV/imunologia , Peroxidase do Rábano Silvestre/química , Humanos , Limite de Detecção , Camundongos , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Estudo de Prova de Conceito , Coelhos
15.
Talanta ; 201: 16-22, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122407

RESUMO

Diode lasers, especially 405 nm diode laser, as excitation sources offer new opportunities for laser-induced fluorescence (LIF) detection, but the lack of available derivatization reagents limits their widespread applications. Herein, a commercial fluorescent dye, 7-(diethylamino)coumarin-3-carboxylic acid (DEAC-C) was introduced as derivatization reagent and corresponding derivatization strategy for DEAC-C labeling sulfonamides was developed for 405 nm LIF detection. After systematic optimization, three sulfonamides including hydrochlorothiazide (HCTZ), chlorothiazide (CTZ) and chlortalidone (CTD) could be efficiently labeled by DEAC-C in the presence of cyanuric chloride and triethylamine (1.5%) in acetonitrile at 50 °C for 180 min. Based on the laboratory-built capillary electrophoresis-LIF system, a robust method was then proposed for the separation of DEAC-C labeled sulfonamides by micellar electrokinetic chromatography (MEKC) using the classic borax-SDS system. Under the optimized conditions, a baseline separation of three sulfonamides was achieved within 15 min, and the detection limits were determined to be 0.24, 0.29, and 0.23 nM for HCTZ, CTZ, and CTD, respectively. Furthermore, the developed MEKC-LIF method was validated using sulfonamide standards and spiked human urine sample and successfully applied for the analysis of three sulfonamides in complex pharmaceutical and physiological samples.

16.
Electrophoresis ; 40(16-17): 2165-2171, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30861170

RESUMO

Micro free flow electrophoresis (µFFE) is a valuable technique capable of high throughput rapid microscale electrophoretic separation along with mild operating conditions. However, the stream flow separation nature of free flow electrophoresis affects its separation performance with additional stream broadening due to sample stream deflection. To reduce stream broadening and enhance separation performance of µFFE, we presented a simple microfluidic device that enables injection bandwidth control. A pinched injection was formed in the reported µFFE system using operating buffer at sample flow rate ratio (r) setting. Initial bandwidth at the entrance of separation chamber can be shrunk from 800 to 30 µm when r increased from 1 to 256. Stream broadening at the exit of separation chamber can be reduced by about 96% when r increased from 4 to 128, according to both theoretical and experimental results. Moreover, the separation resolution for a dye mixture was enhanced by a factor of 4 when r increased from 16 to 128, which corresponded to an 80% reduction in sample initial bandwidth. Furthermore, a similar enhancement on amino acids separation was obtained by using injection control in the reported µFFE device and readily integrated into online/offline sample preparation and/or downstream analysis procedures.


Assuntos
Eletroforese em Microchip/instrumentação , Eletroforese em Microchip/métodos , Aminoácidos/análise , Aminoácidos/isolamento & purificação , Corantes/análise , Corantes/isolamento & purificação , Desenho de Equipamento , Modelos Químicos
17.
Chem Commun (Camb) ; 55(27): 3963-3966, 2019 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-30874265

RESUMO

Flexible control of the micropore size of carbon was achieved in a cost-efficient way by predesigned quantitative correlation between the sizes of extendable (CN2)x nanosized modulators and the generated micropore sizes ranged from 0.2 to 2.3 nm, with effectiveness for boosting the electrochemical performance systematically.

18.
Anal Chim Acta ; 1060: 1-16, 2019 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-30902323

RESUMO

This review (with 152 references) covers the progress made in the development and application of electroosmotic pumps in a period from 2009 through 2018 in microflow analysis. Following a short introduction, the review first categorizes various electroosmotic pumps into five subclasses based on the materials used for pumping: i) open channel EOP, 2) packed-column EOP, iii) porous monolith EOP, iv) porous membrane EOP, and v) other types of EOP. Pumps in each subclass are discussed. A next section covers EOP applications, primarily the applications of EOPs in micro flow analysis and micro/nano liquid chromatography. Other scattered applications are also examined. Perspectives, trends and challenges are discussed in the final section.

19.
Talanta ; 197: 159-167, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30771918

RESUMO

Low-cost and nontoxic fluorescent reagents are important for on-site analysis performed by non-professionals. In this work, a cheap and widely available food additive, caramel was used as an effective fluorescence reagent for the sensitive detection of 2,4,6-trinitrophenol (TNP), 2,4-dinitrophenol (DNP) and 4-nitrophenol (4-NP). Through a simple dialysis, fluorescent components of a commercial caramel were harvested with a yield as high as 60%. The structural characterization demonstrated that the fluorescent components were dehydrated oligomers of carbohydrates. Their fluorescence can be quenched by these nitrophenols. The quenching mechanism was speculated as inner filter effect. At pH 8, a linear range of 0.2-22 µM and a detection limit of 90 nM could be achieved for TNP. Based on the difference of their quenching efficiency at different pHs, TNP, DNP and 4-NP can be simultaneously determined by solving the linear equations obtained at pH 3, 5 and 8. Successful detection of these nitrophenols in the water and soil samples was performed with relative standard deviations of 1.1-5.9% and recoveries of 95-108% of spiked standards.

20.
Electrophoresis ; 40(4): 499-507, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30467879

RESUMO

Aflatoxin contamination in agricultural products poses a great threat to humans and livestock. The aim of this study was to establish a simple, rapid, highly sensitive, and inexpensive method for the simultaneous detection of aflatoxin B1 , B2 , G1 , and G2 in agricultural products. We used a vortex assisted low density solvent-microextraction (VALDS-ME) technique for sample preconcentration and sample detection was achieved with a CE-LIF method. Aflatoxins were separated in an uncoated fused-silica capillary with the MEKC mode and were excited by a 355 nm UV laser to produce native fluorescence for detection. The obtained LOD and LOQ for the four aflatoxins were in the range of 0.002-0.075 and 0.007-0.300 µg/L, respectively, and the analysis time was within 6.5 min. Using the established method, aflatoxins were screened in naturally contaminated dairy cattle feed samples including alfalfa, bran, and corn kernel. The result shows that the alfalfa and bran samples were contaminated with aflatoxins to varying degrees. Compared with other analytical techniques for aflatoxin screening in agricultural products, this CE-LIF method combined with VALDS-ME preconcentration technique is simple, rapid, highly efficient, and inexpensive.


Assuntos
Aflatoxinas/análise , Ração Animal/análise , Cromatografia Capilar Eletrocinética Micelar/métodos , Microextração em Fase Líquida/métodos , Contaminação de Alimentos/análise , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
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