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1.
J Environ Sci Health B ; 55(1): 60-68, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31971076

RESUMO

This work reports the development of a very-simple-to-construct stir-bar extraction device so called "a dumbbell-shaped stainless steel stir-bar." The extraction device was assembled from a rolled up stainless steel net filled with an XAD-2 sorbent and a metal rod to allow the use of a magnetic stirrer during extraction. The dumbbell-shaped stainless steel stir-bar was used to extract diethyl phthalate (DEP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) before analysis by a gas chromatograph equipped with an electron capture detector (GD-ECD). Under the optimal conditions, the developed method provided a good linearity from 10.0 to 1,000.0 ng mL-1 for all three compounds. Limits of detection and limits of quantification were 9.37 ± 0.29 ng mL-1 and 31.22 ± 0.95 ng mL-1 for DEP, 5.73 ± 0.31 ng mL-1 and 19.1 ± 1.0 ng mL-1 for DBP and 3.30 ± 0.06 ng mL-1 and 11.0 ± 0.19 ng mL-1 for DEHP, respectively. Good recoveries in the range of 81.89 ± 0.17 to 109.5 ± 2.0% were achieved when the method was used to extract phthalate esters in five instant noodle and two rice soup samples.


Assuntos
Fracionamento Químico/instrumentação , Análise de Alimentos/instrumentação , Oryza , Ácidos Ftálicos/isolamento & purificação , Aço Inoxidável , Fracionamento Químico/métodos , Cromatografia Gasosa , Dibutilftalato/isolamento & purificação , Dietilexilftalato/isolamento & purificação , Desenho de Equipamento , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Limite de Detecção , Ácidos Ftálicos/química , Reprodutibilidade dos Testes
2.
Anal Chim Acta ; 1091: 30-39, 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31679572

RESUMO

A screw-based portable and simple solid phase microextraction device was fabricated by a 3D printer and used in combination with the developed silver-incorporated porous polyaniline film pencil lead solid-phase microextraction fiber (Ag/PANI SPME). Scanning electron microscopy revealed a porous structure of the electrodeposited Ag/PANI film. The spectrum from energy dispersive x-ray spectroscopy (EDS) and the elemental map confirmed the presence of silver in the porous polymer film. It was used under stirring for the extraction of five phthalate esters: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP). The extracted solution was identified and quantified by gas chromatography using a flame ionization detector (GC-FID). Under the optimum conditions of the developed method, a good linearity was obtained in a concentration range of 5.0-1000 µg L-1 for all five phthalate esters with limits of detection (LODs) of 4.41 ±â€¯0.91 µg L-1, 3.98 ±â€¯0.92 µg L-1, 3.65 ±â€¯0.74 µg L-1, 4.91 ±â€¯0.52 µg L-1 and 4.25 ±â€¯0.66 µg L-1 for DMP, DEP, DBP, BBP and DEHP, respectively. The developed method provided good precision when tested with standard solutions (RSD < 5.5%, n = 6) and real samples (RSD < 3.4%, n = 6). Good fiber-to-fiber reproducibility was also confirmed by extraction with six newly prepared fibers; recoveries ranged from 81.09 ±â€¯0.54% to 92.92 ±â€¯0.46% with RSD <6.6%. The developed method was used to determine phthalate esters in 14 cosmeceutical samples. In rubbing alcohol samples, DEP and DEHP were detected at 7.03 ±â€¯0.76 µg L-1 and 5.89 ±â€¯0.53 µg L-1, respectively, while in contact lens cleaners, DEHP was found in a concentration range from 5.3 ±â€¯1.1 µg L-1 to 6.8 ±â€¯1.2 µg L-1. No phthalate esters contamination was detectable in saline solutions, eye cleaners and antibacterial disinfectant liquids. Recoveries in the range of 81.92 ±â€¯0.99% to 102.4 ±â€¯1.1% indicated the good accuracy of the developed method.


Assuntos
Compostos de Anilina/química , Cosmecêuticos/análise , Ésteres/análise , Grafite/química , Ácidos Ftálicos/análise , Prata/química , 2-Propanol/análise , Adsorção , Cromatografia Gasosa , Soluções para Lentes de Contato/análise , Desinfetantes/análise , Desenho de Equipamento , Limite de Detecção , Impressão Tridimensional , Solução Salina/análise , Microextração em Fase Sólida/instrumentação , Microextração em Fase Sólida/métodos
3.
Sensors (Basel) ; 18(10)2018 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-30347779

RESUMO

Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10-6 and 2.5 × 10-3 M with a detection limit of 5.5 × 10-7 M. On the other hand, MMA-DMA-based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO3- and NH4⁺ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO3- and NH4⁺ with the linear range concentration between 5.0 × 10-5 and 5.0 × 10-2 M (LOD = 11.3 µM) and 5.0 × 10-6 and 1.0 × 10-3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO3- and NH4⁺ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.

4.
Opt Lett ; 43(15): 3730-3733, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30067666

RESUMO

In this Letter, we utilize one-dimensional wavelet analysis to improve the quality of morphology images and velocity profiles of optical coherence tomography simultaneously, by performing analysis on the complex time-frequency plane of raw interferograms, prior to image construction. The results indicate a robust signal improvement that also preserves accuracy for both morphology and velocity information and has been demonstrated on a variety of samples with diverse flow speeds and morphologies.

5.
Talanta ; 188: 658-664, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029427

RESUMO

This article reports the detection of Salmonella spp. based on M13 bacteriophage in a capacitive flow injection system. Salmonella-specific M13 bacteriophage was immobilized on a polytyramine/gold surface using glutaraldehyde as a crosslinker. The M13 bacteriophage modified electrode can specifically bind to Salmonella spp. via the amino acid groups on the filamentous phage. An alkaline solution was used to break the binding between the sensing surface and the analyte to allow renewable use up to 40 times. This capacitive system provided good reproducibility with a relative standard deviation (RSD) of 1.1%. A 75 µL min-1 flow rate and a 300 µL sample volume provided a wide linear range, from 2.0 × 102 to 1.0 × 107 cfu mL-1, with a detection limit of 200 cfu mL-1. Bacteria concentration can be analyzed within 40 min after the sample injection. When applied to test real samples (raw chicken meat) it provided good recoveries (100-111%). An enrichment process was also explored to increase the bacteria concentration, enabling a quantitative detection of Salmonella spp. This biosensor opens a new opportunity for the detection of pathogenic bacteria using bacteriophage.


Assuntos
Carga Bacteriana/métodos , Bacteriófago M13/fisiologia , Técnicas Biossensoriais/métodos , Salmonella/isolamento & purificação , Sequência de Aminoácidos , Animais , Bacteriófago M13/química , Galinhas/microbiologia , Técnicas Eletroquímicas/métodos , Eletrodos , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Ouro/química , Limite de Detecção , Peptídeos/química , Reprodutibilidade dos Testes , Salmonella/química , Ligação Viral
6.
Talanta ; 184: 429-436, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29674065

RESUMO

A portable and simple microextractor device was constructed by aligning six miniaturized multi-stir-rod microextractors. Each microextractor was prepared from rod-like multiwalled carbon nanotubes functionalized with a carboxylic group (MWCNTs-COOH) in composite monoliths that were bundled together and connected to a small DC motor. Using six of these microextractors, the device could extract six samples at the same time. A scanning electron microscope (SEM) showed the MWCNTs-COOH well distributed throughout the highly porous structure of the monolith-MWCNTs-COOH-stir-rod. This miniaturized multi-stir-rod microextractor device was used for the extraction of four parabens, methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP). Under optimized conditions, good linearities were obtained in the concentration range of 1.0 ng mL-1 to 1.0 µg mL-1 for MP and EP and 2.0 ng mL-1 to 1.0 µg mL-1 for PP and BP. The limits of detection were low, 636.2 ±â€¯7.6 pg mL-1 for MP, 675.5 ±â€¯6.0 pg mL-1 for EP, 676.6 ±â€¯8.6 pg mL-1 for PP and 803.4 ±â€¯9.6 pg mL-1 for BP. The developed microextractor could be used up to 15 times (%RSDs from 1.5 to 5.2) and also provided good preparation reproducibility (%RSD from 1.3 to 5.8, n = 6). The % RSDs of intra-day (n = 6) and inter-day (n = 6) precisions were obtained from 1.10-7.79 and 1.96-7.55, respectively. This developed device coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) was applied for the extraction and preconcentration of four parabens in personal care products and cosmetics. The recoveries were studied by spiking the standard solution of parabens in real samples. Good recoveries were obtained in the range of 89.0 ±â€¯2.7 to 102.7 ±â€¯1.8% for MP, 88.09 ±â€¯6.4 to 102.5 ±â€¯1.0% for EP, 83.4 ±â€¯6.4 to 102.9 ±â€¯1.5% for PP and 83.5 ±â€¯3.6 to 102.3 ±â€¯2.0% for BP. This developed device might be easily applied for the extraction and preconcentration of other trace organic compounds in sample matrices.

7.
Mikrochim Acta ; 185(2): 148, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29594556

RESUMO

A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) was prepared for use in micro-solid phase extraction sorbent of preservative agents and antioxidants from cosmetic products. The extracted analytes were quantified by GC-MS. Under the optimized conditions, the calibration plots are linear in the concentration ranges between 5.0 µg·L-1 to 1.0 mg·L-1 for benzoic acid, of 10.0 µg·L-1 to 1.0 mg·L-1 for 2-methyl-3-isothiazolinone (MI), and between 1.0 µg·L-1 and 1.0 mg·L-1 for both 3-tert-butyl-4-hydroxyanisole (BHA) and 2,6-di-tert-butyl-p-hydroxytoluene (BHT). The LODs are 1.0 µg·L-1 for benzoic acid, 5.0 µg·L-1 for MI and 0.5 µg·L-1 for both BHA and BHT. The stir-foam can be easily prepared, is inexpensive and well reproducible (RSDs <3%, for n = 6). It can be re-used for up to 12 times after which extraction efficiency has dropped to 90%. The method was successfully applied to the determination of preservatives and antioxidants in cosmetic samples. Recoveries from spiked samples ranged between 94.5 ± 2.1% and 99.8 ± 1.8%. Graphical abstract A stir foam was prepared from graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) and is shown to be a most viable sorbent for the microextraction of trace amounts of preservative agents and antioxidants from cosmetic products.


Assuntos
Antioxidantes/isolamento & purificação , Conservantes Farmacêuticos/isolamento & purificação , Microextração em Fase Sólida/métodos , Hidroxianisol Butilado/análise , Hidroxitolueno Butilado/análise , Cosméticos/análise , Cromatografia Gasosa-Espectrometria de Massas , Grafite/química , Látex/química , Limite de Detecção , Polietilenoglicóis/química
8.
Biosens Bioelectron ; 102: 217-225, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29149687

RESUMO

A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportional to miRNA-21 concentrations between 0.20fM and 1.0nM, with a very low detection limit of 0.20fM. The biosensor showed a high specificity which could discriminate between complementary, single-, doubled-base mismatched, and non-complementary targets. Three out of the seven tested plasma samples provided detectable concentrations (63 ± 4, 111 ± 4 and 164 ± 7fM). The sensor also showed good recoveries (81-119%). The results indicated the possibilities of this biosensor for analysis without RNA extraction and/or amplification, making the sensor potentially useful for both the prognosis and diagnosis of cancer in clinical application.


Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , MicroRNAs/isolamento & purificação , Hibridização de Ácido Nucleico/genética , Espectroscopia Dielétrica , Ouro/química , Humanos , Limite de Detecção , MicroRNAs/genética , Neoplasias/diagnóstico , Neoplasias/genética , Polímeros/química , Pirróis/química , Pirrolidinas/química , Prata
9.
Anal Chim Acta ; 985: 69-78, 2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28864196

RESUMO

Phthalate esters (PAEs), especially dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP) are widely used as plasticizers in plastics and polymers. They are not chemically bound and can easily migrate into food and human tissue that comes into contact with these materials. The method developed in this work was applied for the preconcentration and determination of these four phthalate esters that might leach from contact lenses and baby teethers. A novel stir-bead micro-solid phase extractor of chitosan cryogel composited with polypyrrole with a steel wire core was evaluated for the extraction of DMP, DEP, DBP and DEHP before analysis by high performance liquid chromatography (HPLC). Scanning electron micrographs of the polypyrrole-chitosan cryogel beads revealed a high porosity with large surface area. Under the optimum conditions, the developed method provided a good linearity in a concentration range from 10 to 750 ng mL-1 for DMP and from 5.0 to 750 ng mL-1 for DEP, DBP and DEHP. The limits of detection (LOD) were 6.07 ± 0.22 ng mL-1, 4.358 ± 0.097 ng mL-1, 4.408 ± 0.099 ng mL-1 and 3.916 ± 0.053 ng mL-1 for DMP, DEP, DBP and DEHP, respectively, and the method reproducibility was good (n = 6, % RSD < 6.0). DBP and DEHP were detected in two original storage solutions of contact lenses from 13.2 ± 1.1 ng mL-1 to 15.4 ± 1.9 ng mL-1 and from 21.3 ± 1.6 ng mL-1 to 23.5 ± 1.5 ng mL-1, respectively. In the artificial saliva in contact with baby teether samples only DEHP was found, from 4.91 ± 0.31 ng mL-1 to 6.78 ± 0.23 ng mL-1, with good recoveries ranging from 81.3 ± 8.4% to 106.3 ± 5.2%.


Assuntos
Quitosana , Soluções para Lentes de Contato/análise , Criogéis , Ácidos Ftálicos/análise , Polímeros , Pirróis , Saliva Artificial/análise , Ésteres , Reprodutibilidade dos Testes
10.
ACS Appl Mater Interfaces ; 9(38): 33368-33376, 2017 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-28846378

RESUMO

Printable organic bioelectronics provide a fast and cost-effective approach for the fabrication of novel biodevices, while the general challenge is to achieve optimized reaction kinetics at multiphase boundaries between biomolecules and electrodes. Here, we present an entirely new concept based on a modular approach for the construction of heterostructured bioelectronic interfaces by using tailored functional "biological microparticles" combined with "transducer microparticles" as modular building blocks. This approach offers high versatility for the design and fabrication of bioelectrodes with a variety of forms of interparticle spatial organization, from layered-structures to more advance bulk heterostructured architectures. The heterostructured biocatalytic electrodes delivered twice the reaction rate and a six-fold increase in the effective diffusion kinetics in response to a catalytic model using glucose as the substrate, together with the advantage of shortened diffusion paths for reactants between multiple interparticle junctions and large active particle surface. The consequent benefits of this improved performance combined with the simple means of mass production are of major significance for the emerging printed electronics industry.


Assuntos
Eletrodos , Biocatálise , Glucose , Cinética , Impressão
11.
Artigo em Inglês | MEDLINE | ID: mdl-28753095

RESUMO

This paper reports the development of a sensitive, high-throughput colorimetric method for the detection of trace mercuric ions (Hg2+). The method is based on the binding of the analyte to gold nanoparticles (AuNPs) modified with Tween-20. Tween-20 was used as a nonionic stabilizer to allow a good dispersion of AuNPs in solution. When mercuric ions were added to the solution, they replaced the Tween-20 stabilizer on the surface of the AuNPs due to their stronger binding affinity. This caused the NPs to aggregate and the color of the solution to change from red to blue. The quantitative analysis of Hg2+ was achieved by plotting the Red Green Blue (RGB) values of the scanned images of the analyte samples in the AuNP solution against concentrations of Hg2+. Since the reaction was carried out in 96-well plates, ninety-six samples were analyzed simultaneously, reducing the cost and time of analysis. The experimental parameters optimized were the concentrations of Tween-20 and NaCl, the reactants ratio, and the incubation time. Under the optimum conditions, the calibration plot of the assay was linear over an Hg2+ concentration range of 0.10-2.00 mg L-1, and the detection limit was 0.050 mg L-1 (S/N  =  3). The selectivity of the technique was high with no significant colorimetric responses to the presence of 100-fold excesses of other metal ions. Quantification was validated with Hg2+ standard solutions and spiked tap and waste water samples, and the accuracy of the technique was confirmed. The developed technique is simple and cost effective because it requires no complicated instruments, yet the results demonstrate it to be a very powerful technique with the potential to be developed for on-site mercury detection.


Assuntos
Colorimetria/métodos , Ouro/química , Mercúrio/análise , Nanopartículas Metálicas/química , Polissorbatos/química , Poluentes Químicos da Água/análise , Íons , Limite de Detecção
12.
Biosens Bioelectron ; 96: 84-88, 2017 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-28463740

RESUMO

A simple renewable surface for a rapid antibacterial susceptibility test has been demonstrated. The 3-aminophenylboronic acid (3-APBA) modified electrode bind with cis-diol groups on the cell wall of both gram positive and gram negative bacteria. The detection of antibacterial susceptibility response by a capacitive system can be done within a short time, 2.5h for the whole process, with good repeatability of the electrode's preparation. An acid solution, could break the bonding between 3-APBA and the bacteria, which were then easily removed by the fluid flow, renewing the sensing surface for the next test. This modified electrode can be reused up to 35 times. This sensor is useful for testing the susceptibility of bacteria to antibacterial agents that affect their cell wall. Results from the capacitive sensor corresponded well with the antimicrobial information in the literature and to the morphology of the treated bacteria revealed by scanning electron microscopy. Antimicrobial susceptibility to natural products could also be easily tested.


Assuntos
Antibacterianos/farmacologia , Ampicilina/farmacologia , Técnicas Biossensoriais , Ácidos Borônicos/farmacologia , Ceftriaxona/farmacologia , Técnicas Eletroquímicas , Eletrodos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície , Tetraciclina/farmacologia , Vancomicina/farmacologia , Xantonas/farmacologia
13.
Talanta ; 167: 573-582, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28340763

RESUMO

A novel preconcentrator-separator two-in-one online system has been developed for the online analysis of trace amounts of four polycyclic aromatic hydrocarbons (PAHs) in tea samples. A micro-preconcentrator unit of zeolite imidazolate framework-8-poly(vinyl alcohol) cryogel (ZIF-8-PVA cryogel) and a micro-separation unit of multiwalled carbon nanotubes-poly(vinyl alcohol) cryogel (MWCNTs-PVA cryogel) were fabricated onto an acrylic plate. The eluent from this two-in-one system flowed directly to an on-column UV-visible detector. Under optimum conditions, the system provided a wide linear range from 0.10µgL-1 to 2.00mgL-1 for benzo(a)anthracene (BaA) and chrysene (Chry), 0.15µgL-1 to 3.00mgL-1 for benzo(a)pyrene (BaP) and 0.20µgL-1 to 5.00mgL-1 for benzo(b)fluoranthene (BbF). The limits of detection were 0.05µgL-1 of both BaA and Chry, 0.10µgL-1 of BaP and 0.20µgL-1 of BbF. This two-in-one system was cost-effective, easy to prepare, had excellent stability for up to 417 consecutive injection cycles and provided a good system-to-system reproducibility (n=6) with a relative standard deviation of less than 4%. The system was successfully applied to detect PAHs in tea samples. The concentrations of BaA, Chry, BaP and BbF in seven tea samples were found in the range of non-detectable 2.73±0.07mgL-1 with good recoveries of 83±6 to 108±4%. In addition, it can be easily applied for the detection of other aromatic compounds in contaminated water samples.

14.
Artigo em Inglês | MEDLINE | ID: mdl-27533342

RESUMO

Two important air pollutants, sulfur dioxide (SO2) and nitrogen dioxide (NO2), were sampled and monitored in the spring season in the biggest industrial area of Bhutan. Field measurements of SO2 and NO2 were performed using standard colorimetric methods, and air samples were collected using an active sampling technique. Sampling sites were selected to cover all the potential catchment areas like settlements, staff quarters, shops and schools. The main objective of this sampling work was to see the distribution of these two pollutants from the source of emission (small scale industries) and to obtain and establish a baseline data. The active sampler was first tested and validated in a laboratory using liquid and gas standards of SO2 and NO2. Good linearity from 0.050 to 1.0 µg mL-1 for SO2 and from 0.010 to 1.0 µg mL-1 for NO2 were obtained (R2 > 0.99) with limits of detection of 30 and 50 ng mL-1 for SO2 and NO2, respectively. Daylong sampling was done at selected sites with a range of distances away from the sources of emission. The ambient concentration of SO2 and NO2 were in the range of 0.45-4.46 and 0.56-5.68 µg m-3, respectively.


Assuntos
Poluentes Atmosféricos/análise , Dióxido de Nitrogênio/análise , Dióxido de Enxofre/análise , Butão , Monitoramento Ambiental , Indústrias , Estações do Ano
15.
Biosens Bioelectron ; 85: 743-750, 2016 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-27266659

RESUMO

A simple and selective colorimetric sensor for sialic acid detection, based on the aggregation of 4-mercaptophenylboronic acid functionalized gold nanoparticles (4-MPBA-AuNPs) was developed. The color of the solution changed from wine-red to blue after binding with sialic acid. The colorimetric sensor provided good analytical performances with a linear dynamic range of 80µM to 2.00mM and a 68±2µM limit of detection without any effect from possible interferences and sample matrix. In addition, the quantitative results were obtained within only 10min. This developed sensor was used to detect sialic acid in blood serum samples and the results were in good agreement with those from the current periodate-resorcinol method (P>0.05) thus indicating that this developed colorimetric sensor can be used as an alternative method for sialic acid detection with a shorter analysis time and a high accuracy.


Assuntos
Ácidos Borônicos/química , Colorimetria/métodos , Ouro/química , Nanopartículas Metálicas/química , Ácido N-Acetilneuramínico/sangue , Compostos de Sulfidrila/química , Técnicas Biossensoriais/métodos , Humanos , Limite de Detecção , Nanopartículas Metálicas/ultraestrutura
16.
Artigo em Inglês | MEDLINE | ID: mdl-27231039

RESUMO

A laboratory-built printed circuit board (PCB) passive sampler used for the monitoring of xylene and styrene in copy print shops was re-validated for detecting benzene, toluene and xylene (BTX) and applied for the sampling of ambient air from Hat Yai city, Songkhla, Thailand, in the month of November 2014. For monitoring, the PCB passive samplers were exposed to target analytes in 16 locations covering high to low exposure areas. After sampling, the samplers were thermally desorbed and the analytes were trapped by multi-walled carbon nanotubes packed into a micro-preconcentrator coupled to a gas chromatograph (GC) equipped with a flame ionization detector. At the optimum GC operating conditions, the linear dynamic ranges for BTX were 0.06-5.6 µg for benzene, 0.07-2.2 µg for toluene and 0.23-2.5 µg for xylene with R(2) > 0.99 with the limits of detection being 6.6, 6.8 and 19 ng for benzene, toluene and xylene, respectively. The concentrations of BTX in the 16 sampling sites were in the range of N.D.-1.3 ± 1.6, 4.50 ± 0.76-49.6 ± 3.7 and 1.00 ± 0.21-39.6 ± 3.1 µg m(-3), respectively. When compared to past studies, there had been an increase in the benzene concentration.


Assuntos
Poluentes Atmosféricos/análise , Benzeno/análise , Monitoramento Ambiental/métodos , Tolueno/análise , Xilenos/análise , Cromatografia Gasosa , Cidades , Nanotubos de Carbono , Tailândia
17.
Talanta ; 155: 305-13, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27216687

RESUMO

In this work, the idea of incorporating a non-enzymatic signal amplification with a regular aptasensor was tested. In this proof of principle, the sensor was designed for the detection of mercury (II) ions (Hg(2+)) based on the Förster Resonance Energy Transfer (FRET), and the catalyzed hairpin assembly (CHA) technique that was used as the signal amplification method. This sensor comprised a mercury aptamer-catalyst complex (Apt-C) and two types of hairpin DNA: H1 labeled with fluorescein and H2 labeled with tetramethylrhodamine. In the presence of Hg(2+), two facing thymine bases in the mercury aptamer strand were coordinated with one mercury ion. This caused the release of the catalyst for the catalyzed hairpin assembly (CHA) reaction that turned H1 and H2 hairpins into H1-H2 hybrids. FRET was then used to report the hairpin-duplex transformation. The sensor showed excellent specificity towards Hg(2+) over other possible interfering cations present at even a 100 fold greater concentrations. It had a linear range of 10.0-200.0nM, and a good detection limit of 7.03±0.18nM, which is lower than the regulatory mercury limit for drinking water (10nM or 2ppb). The sensor was used to detect spiked Hg(2+) in nine real surface water samples collected from three different areas. Acceptable recoveries and small standard deviations indicated that the sensor was practically applicable, and the proposed idea to incorporate a CHA amplification in a regular aptasensor was not only feasible but beneficial. The same principles can be applied to develop sensors for various different targets.

18.
Biosens Bioelectron ; 82: 99-104, 2016 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-27054813

RESUMO

A highly sensitive label-free DNA biosensor based on PNA probes immobilized on a gold electrode was used to detect a hybridization event. The effect of a target DNA overhang on the hybridization efficiency was shown to enhance the detected signal and allowed detection at a very low concentration. The sensors performances were investigated with a complementary target that had the same length as the probe, and the signal was compared to the target DNAs with different lengths and overhangs. A longer target DNA overhang was found to provide a better response. When the overhang was on the electrode side the signal enhancement was greater than when the overhang was on the solution side due to the increased thickness of the sensing surface, hence produced a larger capacitance change. Using conformationally constrained acpcPNA probes, double stranded DNA was detected sensitively and specifically without any denaturing step. When two acpcPNA probes were applied for the screening test for the double stranded HLA-B*58:01 and HLA-B*57:01 genes that are highly similar, the method differentiated the two genes in all samples. Both purified and unpurified PCR products gave comparable results. This method would be potentially useful as a rapid screening test without the need for purification and denaturation of the PCR products.


Assuntos
Técnicas Biossensoriais/métodos , DNA/genética , Antígenos HLA-B/genética , Sequência de Bases , DNA/análise , Capacitância Elétrica , Humanos , Hibridização de Ácido Nucleico/métodos , Sondas de Ácido Nucleico/química , Sondas de Ácido Nucleico/genética , Ácidos Nucleicos Peptídicos/química , Ácidos Nucleicos Peptídicos/genética
19.
Anal Chim Acta ; 917: 27-36, 2016 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-27026597

RESUMO

A novel miniaturized "stir-brush microextractor" was prepared using a zinc oxide/hydroxylated multiwalled carbon nanotubes (ZnO/MWCNTs-OH) coated stainless steel brush connected to a small dc motor. The synthesized zinc oxide on each strand of stainless steel had a flower-like nanostructure when observed by a scanning electron microscope (SEM). This structure produced a large surface area before it was coated with the hydroxylated multiwalled carbon nanotubes sorbent. Under optimal conditions, the developed device provided a good linearity for the extraction of carbofuran and carbaryl, in the range of 25-500 ng mL(-1) and 50-500 ng mL(-1), respectively, with low limits of detection of 17.5 ± 2.0 ng mL(-1) and 13.0 ± 1.8 ng mL(-1). It also provided a good stir-brush-to-stir-brush reproducibility (% relative standard deviation < 5.6%, n = 6). The device was applied for the extraction and preconcentration of carbamate pesticides in fruit and vegetable samples prior to analysis with a gas chromatograph coupled with a flame ionization detector (GC-FID). Carbofuran was found at 9.24 ± 0.93 ng g(-1) and carbaryl was detected at 7.05 ± 0.61 ng g(-1) with good recoveries in the range of 73.7 ± 10.0% to 108.4 ± 2.6% for carbofuran and 75.7 ± 10.0% to 111.7 ± 5.7% for carbaryl.


Assuntos
Carbamatos/análise , Miniaturização , Nanotubos de Carbono , Praguicidas/análise , Óxido de Zinco/química , Cromatografia Gasosa , Hidroxilação , Microscopia Eletrônica de Varredura , Reprodutibilidade dos Testes
20.
J Sep Sci ; 38(22): 3921-3927, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26347144

RESUMO

A magnetic solid-phase extraction sorbent of polypyrrole/silica/magnetite nanoparticles was successfully synthesized and applied for the extraction and preconcentration of sulfonamides in water samples. The magnetite nanoparticles provided a simple and fast separation method for the analytes in water samples. The silica coating increased the surface area that helped to increase the polypyrrole layer. The polypyrrole-coated silica provided a high extraction efficiency due to the π-π and hydrophobic interactions between the polypyrrole and sulfonamides. Several parameters that affected the extraction efficiencies, i.e. the amount of sorbent, pH of the sample, extraction time, extraction temperature, ionic strength, and desorption conditions were investigated. Under the optimal conditions, the method was linear over the range of 0.30-200 µg/L for sulfadiazine and sulfamerazine, and 1.0-200 µg/L for sulfamethazine and sulfamonomethoxine. The limit of detection was 0.30 µg/L for sulfadiazine and sulfamerazine and 1.0 µg/L for sulfamethazine and sulfamonomethoxine. This simple and rapid method was successfully applied to efficiently extract sulfonamides from water samples. It showed a high extraction efficiency for all tested sulfonamides, and the recoveries were in the range of 86.7-99.7% with relative standard deviations of < 6%.

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