Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 96
Filtrar
1.
Talanta ; 235: 122818, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34517674

RESUMO

As a type of environmental endocrine disrupting chemicals, bisphenols (BPs) have a certain embryonic toxicity and teratogenicity, which can significantly increase the risks of breast cancer, prostate cancer, leukemia and other cancers. In this work, stable multivariate metal-organic frameworks (UiO-66-NH2/TCPPx) were synthesized via in situ one-pot method and used as miniaturized dispersive solid-phase extraction (dµSPE) sorbents for extraction of trace BPs from environmental samples. The phase purity, crystal morphology and physical properties of UiO-66-NH2/TCPPx samples were varied by adjusting the mass ratio of TCPP. The extraction performance of UiO-66-NH2/TCPPx samples were investigated and UiO-66-NH2/TCPP1.0 exhibited the highest adsorption efficiency. Besides, UiO-66-NH2/TCPP1.0 possessed excellent recycling stability for the adsorption and desorption of BPs more than 20 cycles. The experimental parameters including amount of adsorbent, adsorption time, sample solution pH, temperature, desorption time and desorption solvents which affecting the efficiency of dµSPE were studied, respectively. Good linearity (R2 > 0.9992) in range of 0.1-200 ng mL-1 was obtained. The detection limits (S/N = 3) and quantification limits (S/N = 10) were achieved at 0.03-0.08 ng mL-1 and 0.1-0.5 ng mL-1, respectively. The relative standard deviations (RSDs) of intra-day and inter-day ranged from 2.5 to 5.5% and 1.1-6.8%. Enrichment factors were calculated in the range of 303-338. The obtained recoveries of bisphenol F (BPF), bisphenol A (BPA), bisphenol B (BPB) and bisphenol AF (BPAF) were 81.26-91.03% (RSDs = 0.96-6.47%), 82.2-97.27% (RSDs = 0.45-6.15%), 87.56-97.26% (RSDs = 1.1-6.22%) and 82.2-100.8% (RSDs = 0.46-4.07%). The UiO-66-NH2/TCPP1.0 can be employed as potential dµSPE sorbents for the enrichment of trace BPs in the environmental samples.


Assuntos
Estruturas Metalorgânicas , Adsorção , Compostos Benzidrílicos , Humanos , Masculino , Fenóis , Extração em Fase Sólida , Solventes
2.
Mikrochim Acta ; 188(10): 340, 2021 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-34523015

RESUMO

Using MIL-101(Fe) as the source of carbon and Fe, a magnetic porous carbon (MPC) material with Fe3C nanoparticles encapsulated in porous carbon was prepared through one-pot pyrolysis under N2 atmosphere. With MPC as adsorption material, a stir bar sorptive-dispersive microextraction (SBSDME) method was proposed to extract and preconcentrate sulfonamides (SAs) prior to HPLC-DAD determination. To investigate their extraction ability, different MPC materials were prepared under different carbonization temperatures (600, 700, 800, 900, and 1000 °C). The material prepared under 900 °C (MPC-900) exhibited the highest extraction ability for SAs. The as-prepared MPC materials were also characterized by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, zeta potential, and other techniques. The main parameters that affect extraction were systematically studied. Under optimal conditions, favorable linearity (R2 ≥ 0.9938) and detection limits (0.02-0.04 ng mL-1) of sulfonamides were obtained. The average recoveries for spiked milk and lake water samples ranged from 76.9 to 109% and from 75.4 to 118% with RSDs of 3.10-9.63% and 1.71-11.3%, respectively. Sulfameter and sulfisoxazole were detected in milk sample. Sulfisoxazole was detected in the lake water sample. The MPC-900 material demonstrated excellent reusability. It can be reused 24 times with peak areas having no obvious decline. The method can be applied to extract ultra-trace compounds in complex sample matrices. Schematic presentation of a stir bar sorptive-dispersive microextraction (SBSDME) by using magnetic porous carbon (MPC) composites as sorbent combined with high-performance liquid chromatography for sensitive analysis of sulfonamides in milk and lake water samples.

3.
Chem Commun (Camb) ; 57(70): 8810-8813, 2021 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-34382969

RESUMO

Herein, a new gas-cycle-assisted (GCA) headspace solid-phase microextraction (HS-SPME) device was designed to rapidly extract organic pollutants with high Kow and boiling points, which have difficulty in volatilization from matrix to headspace. Organic pollutants, including three polycyclic aromatic hydrocarbons (PAHs), four polychlorinated biphenyls (PCBs), and five phthalate esters (PAEs), were selected to evaluate the performance of GCA HS-SPME. Compared with conventional HS-SPME, the equilibrium times of GCA HS-SPME for extraction of PAHs, PCBs, and PAEs were greatly shortened from 70-90 to 5-11 min. Moreover, the limits of detection for analysis of PAHs were achieved at pg mL-1 level by GCA HS-SPME coupled with gas chromatography-flame ionization detection.

4.
J Chromatogr A ; 1649: 462236, 2021 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-34038777

RESUMO

The widespread presence of lipid hydroperoxides in foodstuffs and biological samples has aroused great attentions in recent years, while it remains challenging for analysis of the fragility of O - O bond linkage of peroxides. In this present study, we explored the utility of electrospray ionization mass spectrometry (ESI-MS) for characterization of two fatty acid hydroperoxides from oxidation of linoleic acid and α-linolenic acid, which are the essential fatty acids abundant in many seeds and vegetable oils. The results indicated that in-source fragmentation occurred in the detection of the two fatty acid hydroperoxides in both positive and negative ion modes, which yielded characteristic fragments for ESI-MS analysis. In addition, the genotoxicity of fatty acid hydroperoxides for generation of nucleoside adducts was investigated. It was found that a variety of nucleoside adducts were formed from the reactions of fatty acid hydroperoxides and nucleosides. Furthermore, the decomposition products of the fatty acid hydroperoxides were determined, which provided evidence to elucidate the reaction mechanism for formation of nucleoside adducts.


Assuntos
Ácidos Graxos/química , Ácidos Linoleicos/química , Ácidos Linolênicos/química , Peróxidos Lipídicos/química , Nucleosídeos/química , Cromatografia Líquida de Alta Pressão/métodos , Oxirredução , Óleos Vegetais/química , Espectrometria de Massas por Ionização por Electrospray/métodos
5.
J Environ Sci (China) ; 103: 80-92, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33743921

RESUMO

In this study, transport behaviors of graphene oxide (GO) in saturated uncoated (i.e., clean sand) and goethite-coated sand porous media were examined as a function of the phosphate. We found that phosphate enhanced the transport of GO over a wide range of solution chemistry (i.e., pH 5.0-9.0 and the presence of 10 mmol/L Na+ or 0.5 mmol/L Ca2+). The results were mainly ascribed to the increase of electrostatic repulsion between nanoparticles and porous media. Meanwhile, deposition site competition induced by the retained phosphate was another important mechanism leading to promote GO transport. Interestingly, when the phosphate concentration increased from 0.1 to 1.0 mmol/L, the transport-enhancement effect of phosphate in goethite-coated sand was to a much larger extent than that in clean sand. The observations were primarily related to the difference in the total mass of retained phosphate between the iron oxide-coated sand and clean sand columns, which resulted in different degrees of the electrostatic repulsion and competitive effect of phosphate. When the background solution contained 0.5 mmol/L Ca2+, phosphate could be bind to sand/ goethite-coated sand surface by cation bridging; and consequently, promoted competition between phosphate and nanoparticles for deposition sites, which was an important mechanism for the enhanced effect of phosphate. Moreover, the DLVO theory was applicable to describe GO transport behaviors in porous media in the absence or presence of phosphate. Taken together, these findings highlight the important status and role of phosphate on the transport and fate of colloidal graphene oxide in the subsurface environment.


Assuntos
Nanopartículas , Dióxido de Silício , Compostos Férricos , Grafite , Fosfatos , Porosidade , Areia
6.
Food Chem ; 343: 128472, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33139121

RESUMO

Cadmium is a toxic environmental pollutant that is readily absorbed by rice grains and poses serious threats to human health. The selection and breeding of rice varieties with low cadmium accumulation is one of the most economical and ecological methods to reduce cadmium exposure. In this study, two different indica rice grains under cadmium stress were subjected to mass spectrometry-based metabolomics analysis for the first time. When the cadmium concentration increased in rice grains, most carbohydrates and amino acids were down-regulated, except myoinositol that can prevent cadmium toxicity, which was up-regulated. d-Mannitol and l-cysteine were up-regulated with the increase of cadmium concentration in low-cadmium-accumulating rice. Also, organic acids were activated especially 13-(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoicacid that is related to the alpha-linolenic acid metabolism and jasmonic acid production. The determination of biomarkers and characterization of metabolic pathways might be helpful for the selection of rice varieties with low cadmium accumulation.


Assuntos
Cádmio/toxicidade , Oryza/efeitos dos fármacos , Oryza/metabolismo , Poluentes do Solo/toxicidade , Aminoácidos/metabolismo , Biomarcadores/análise , Biomarcadores/metabolismo , Cádmio/farmacocinética , Metabolismo dos Carboidratos/efeitos dos fármacos , Ciclopentanos/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Ácidos Linolênicos/metabolismo , Peróxidos Lipídicos/metabolismo , Manitol/metabolismo , Espectrometria de Massas , Metabolômica/métodos , Oryza/química , Oxilipinas/metabolismo , Estruturas Vegetais/química , Poluentes do Solo/farmacocinética
7.
Chemosphere ; 265: 129081, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33288283

RESUMO

Since iron oxide minerals are ubiquitous in natural environments, the release of graphene oxide (GO) into environmental ecosystems can potentially interact with iron oxide particles and thus alter their surface properties, resulting in the change of their transport behaviors in subsurface systems. Column experiments were performed in this study to investigate the co-transport of GO nanoparticles and hematite colloids (a model representative of iron oxides) in saturated sand. The results demonstrated that the presence of hematite inhibited GO transport in quartz sand columns due to the formation of less negatively charged GO-hematite heteroaggregates and additional deposition sites provided by the adsorbed hematite on sand surfaces. Contrarily, GO co-present in suspensions significantly enhanced the transport of hematite colloids through different mechanisms such as the increase of electrostatic repulsion, decreased physical straining, GO-facilitated transport of hematite (i.e., highly mobile GO nanoparticles served as a mobile carrier for hematite). We also found that the co-transport behaviors of GO and hematite depended on solution chemistry (e.g., pH, ionic strength, and divalent cation (i.e., Ca2+)), which affected the electrostatic interaction as well as heteroaggregation behaviors between GO nanoparticles and hematite colloids. The findings provide an insight into the potential fate of carbon nanomaterials affected by mineral colloids existing in natural waters and soils.


Assuntos
Grafite , Nanopartículas , Coloides , Ecossistema , Compostos Férricos , Concentração Osmolar , Porosidade , Dióxido de Silício
8.
J Chromatogr A ; 1626: 461354, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797834

RESUMO

The Al-doped mesoporous crystalline material-41 (Al-MCM-41) composite was prepared and applied as fiber coating material of headspace solid-phase microextraction (HS-SPME) for extraction of polycyclic aromatic hydrocarbons (PAHs) from human urine. Five PAHs including acenaphthene, fluorene, phenanthrene, anthracene, and pyrene are chosen as target analytes to evaluate the performance of the material by GC-FID analysis. The mesoporous Al-MCM-41 composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption measurement, and thermogravimetric analysis. The parameters affecting the extraction efficiency of HS-SPME were investigated. Under the optimal conditions, the method exhibits ideal linearity for target analytes in the range of 0.3-600 ng⋅mL-1 with the coefficients (R2) equal or higher than 0.9906. The enrichment factors are calculated from 540 to 1760. The limits of detection (LODs) and limits of quantitation (LOQs) are between the ranges of 0.06-0.18 and 0.3-0.9 ng⋅mL-1, respectively. The relative standard deviations (RSDs) (n = 5) of intra-day and inter-day are in the ranges of 1.08-7.49% and 2.84-18.3% respectively. The fiber-to-fiber reproducibility (n = 3) is in the range of 6.47-13.9%. The method was successfully applied for the analysis of PAHs in human urine with reasonable recoveries which is ranging from 73.29 to 116.1%.


Assuntos
Alumínio/química , Hidrocarbonetos Policíclicos Aromáticos/urina , Dióxido de Silício/química , Microextração em Fase Sólida/métodos , Adsorção , Cristalização , Humanos , Limite de Detecção , Masculino , Concentração Osmolar , Porosidade , Padrões de Referência , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Fatores de Tempo , Difração de Raios X
9.
Mikrochim Acta ; 187(6): 367, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32494885

RESUMO

The monodispersed mesoporous SiO2@metal-organic framework (MSN@MIL-101(Fe)) composites were prepared by grafting MSN-NH2 onto MIL-101(Fe) particles with a solvothermal method. The adsorption ability of the composites was greatly improved compared to that of pristine MSNs or MIL-101(Fe) for phytohormones (Phys). The MSN@MIL-101(Fe) composites were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive spectrometer, and mapping analysis. Using MSN@MIL-101(Fe) composites as sorbent, a dispersive solid-phase extraction procedure (dSPE) was developed to extract three endogenous Phys (abscisic acid (ABA), indole-3-aceticacid (IAA), and indole-3-butyric acid (IBA)) and two exogenous Phys (1-naphthylacetic acid (1-NAA) and 2-naphthylacetic acid (2-NAA)) prior to HPLC-DAD analysis. The experimental parameters including sample volume, sorbent amount, adsorption time, adsorption pH, desorption time, and desorption solvent on extraction efficiency were optimized and evaluated. Under optimized conditions, the working range of 0.08 to 0.45 ng mL-1 with enrichment factors from 144 to 207 were achieved. The linear range is 0.75-200 ng mL-1 for IAA, 0.20-200 ng mL-1 for ABA, and 1.0-200 ng mL-1 for IBA, 1-NAA, and 2-NAA. With MSN@MIL-101(Fe) as sorbent for extraction of Phys and determination by HPLC-DAD, two endogenous Phys (IAA and ABA) were detected from mung bean sprouts which were made in a laboratory, and the results were further confirmed by high-resolution mass spectrometry. The composites can be applied to extract other small molecules, which have similar chemical structures with Phys in biological, environmental, and food samples. Graphical abstract Schematic presentation of a dispersive solid-phase extraction using monodispersed mesoporous SiO2@metal-organic framework composites (MSNs@MIL-101(Fe)) as the sorbent for extraction, clean-up, and preconcentration of phytohormones in mung bean sprouts prior to HPLC-DAD analysis.

10.
J Agric Food Chem ; 68(26): 6956-6966, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32516537

RESUMO

Many physicochemical changes occur during food storage and processing, such as rancidity, hydrolysis, oxidation, and aging, which may alter the taste, flavor, and texture of food products and pose risks to public health. Analysis of these changes has become of great interest to many researchers. Mass spectrometry is a promising technique for the study of food and nutrition domains as a result of its excellent ability in molecular profiling, food authentication, and marker detection. In this review, we summarized recent advances in mass spectrometry techniques and their applications in food storage and processing. Furthermore, current technical challenges associated with these methodologies were discussed.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas/métodos , Manipulação de Alimentos , Armazenamento de Alimentos
11.
Talanta ; 208: 120440, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31816803

RESUMO

Reduced graphene oxide/ZnFe2O4 (rGO/ZnFe2O4) nanocomposite was facile prepared and applied as magnetic sorbent for the extraction of estrogens including 17ß-estradiol, 17α-estradiol, estrone and hexestrol from water, soil, and fish samples prior to HPLC analysis. The rGO/ZnFe2O4 nanocomposite was characterized by scanning electron microscope, Fourier transform-infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The experimental parameters affecting the efficiency of magnetic solid-phase extraction (MSPE) including the amount of material, extraction time, pH, temperature, desorption solvents, desorption time, and desorption solvent volume were investigated respectively. With the developed method, good linearity was observed in the range of 0.05-500 ng/mL with the correlation coefficients (R2) between 0.9978 and 0.9993. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were achieved at 0.01-0.02 ng/mL and 0.05 ng/mL, respectively. The enrichment factors were calculated as the range of 241-288. Using rGO/ZnFe2O4 nanocomposite as the sorbent, the developed MSPE followed by HPLC analysis, was applied to analysis of estrogens in river water, soil and fish samples. The method has the potential application in the extraction and preconcentration ultra trace compounds in complex matrices, such as environmental and biological samples.


Assuntos
Estrogênios/química , Compostos Férricos/química , Grafite/química , Nanocompostos/química , Zinco/química , Adsorção , Animais , Peixes , Fenômenos Magnéticos , Solo/química , Água/química
12.
Chem Commun (Camb) ; 55(67): 10019-10022, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31378803

RESUMO

We report a facile hydrothermal method to synthesize a novel mesoporous graphitic carbon nitride (MCN)@NiCo2O4 nanocomposite, which can be used as a solid phase microextraction coating for high efficiency extraction and preconcentration of trace polychlorinated biphenyls and polycyclic aromatic hydrocarbons in human serum samples.


Assuntos
Poluentes Ambientais/sangue , Nanocompostos/química , Nitrilas/química , Bifenilos Policlorados/sangue , Hidrocarbonetos Policíclicos Aromáticos/sangue , Cobalto/química , Humanos , Limite de Detecção , Níquel/química , Microextração em Fase Sólida/instrumentação , Microextração em Fase Sólida/métodos
13.
Nat Commun ; 10(1): 1768, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30992454

RESUMO

Seed germination and photoautotrophic establishment are controlled by the antagonistic activity of the phytohormones gibberellins (GAs) and abscisic acid (ABA). Here we show that Arabidopsis thaliana GAS2 (Gain of Function in ABA-modulated Seed Germination 2), a protein belonging to the Fe-dependent 2-oxoglutarate dioxygenase superfamily, catalyzes the stereospecific hydration of GA12 to produce GA12 16, 17-dihydro-16α-ol (DHGA12). We show that DHGA12, a C20-GA has an atypical structure compared to known active GAs but can bind to the GA receptor (GID1c). DHGA12 can promote seed germination, hypocotyl elongation and cotyledon greening. Silencing and over-expression of GAS2 alters the ABA/GA ratio and sensitivity to ABA during seed germination and photoautotrophic establishment. Hence, we propose that GAS2 acts to modulate hormonal balance during early seedling development.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Dioxigenases/metabolismo , Giberelinas/metabolismo , Plântula/crescimento & desenvolvimento , Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/genética , Dioxigenases/genética , Mutação com Perda de Função , Plantas Geneticamente Modificadas , Sementes/metabolismo
14.
Mikrochim Acta ; 186(5): 279, 2019 04 11.
Artigo em Inglês | MEDLINE | ID: mdl-30976897

RESUMO

Mesoporous graphitic carbon nitride (MCN) is shown to be a viable sorbent for the enrichment of sulfonamides (SAs). To overcome the difficulty of separating the sorbent from the matrix, a novel type kind of column-assisted dispersive solid-phase extraction (CA-dSPE) method was designed. The MCN was characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, fourier transform infrared spectroscopy and nitrogen adsorption-desorption measurements. The amount of sorbent, the pH value of the sample, the adsorption time, type and volume of the eluent and desorption time were optimized. The SAs were eluted from the sorbent with elution solvent of methanol containing 10% (v/v) ammonia and then submitted to HPLC analysis. Under the optimized conditions, the limits of detection for the SAs investigated (sulfadiazine, sulfameter, sulfachloropyridazine, sulfabenzamide and sulfadimethoxine) range from 20 to 5 pg·mL-1. Satisfactory recoveries were obtained for spiked environmental water (90.1-110.5%) and milk samples (82.3-102.7%), with relative standard deviations of 0.5-3.8% and 1.1-4.4%, respectively. The method is simple, time saving and sensitive. Graphical abstract Schematic presentation of a column assisted dispersive solid-phase extraction by using mesoporous graphitic carbon nitride as sorbent combined with high performance liquid chromatography for sensitive analysis of sulfonamides in environmental water and milk samples.

15.
Spectrochim Acta A Mol Biomol Spectrosc ; 213: 228-234, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30695741

RESUMO

In this work, we reported an economical plant-based hydrothermal method for one-pot green synthesis of water-soluble carbon dots (Tea-CDs) by using waste tea extract as a carbon source. The synthesized Tea-CDs were characterized by UV-visible, fluorescence, FT-IR, TEM, XPS and XRD. The Tea-CDs were found to remove hydroxyl and superoxide anion radical in vitro. In addition, the Tea-CDs exhibited bright blue fluorescence under UV-light (λex = 365 nm), and the fluorescence could be effectively quenched by CrO42- and Fe3+ ions. Meanwhile, the fluorescence of Tea-CDs-CrO42- and Tea-CDs-Fe3+ systems could be again easily recovered by ascorbic acid (AA) and L-cysteine (L-Cys). As an on-off-on fluorescent nano-sensor of the Tea-CDs, the sensitive detection of CrO42-, Fe3+, AA and L-Cys were all performed, showing that the good linear relationships between fluorescence intensity of Tea-CDs and concentration of all testing samples. Finally, the sensors successfully detected CrO42-, Fe3+, AA and L-Cys in commercially available real samples with satisfactory recovery ranges. The prepared sensors offer distinct advantages including low cost, simple handling, good sensitivity and high selectivity.


Assuntos
Antioxidantes/análise , Ácido Ascórbico/análise , Carbono/química , Compostos de Cromo/análise , Cisteína/análise , Ferro/análise , Pontos Quânticos/química , Chá/química , Ácido Ascórbico/urina , Compostos de Cromo/urina , Cisteína/urina , Sequestradores de Radicais Livres/química , Radicais Livres/química , Concentração de Íons de Hidrogênio , Ferro/urina , Espectroscopia Fotoeletrônica , Pontos Quânticos/ultraestrutura , Cloreto de Sódio/química , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
16.
Anal Chim Acta ; 1038: 21-28, 2018 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-30278904

RESUMO

This work reports the proof-of-concept of an ultrasensitive label-free electrochemical aptasensor for Kanamycin (Kana) detection coupling strand-displacement amplification (SDA) with hybridization chain reaction (HCR). In the presence of target Kana, the analyte triggers conformational change of hairpin HP1 (HP1) and two-staged SDA to produce short single-stranded DNA (S1) with the aid of KF polymerase and nicking endonuclease. Meanwhile, the as-produced S1 hybridizes with the immobilized hairpin HP2 (HP2) on the electrode to open the hairpin, thereby resulting in the formation of DNA duplex. Thereafter, DNA duplex is selectively digested by Exo III accompanying S1 recycling. The residual single-stranded probe (S2) on the electrode opens another two hairpins in sequence and propagates a chain reaction of hybridization events between two alternating hairpins (H1 and H2) to form a long nicked double-helix. Upon addition of redox-active methylene blue (MB), numerous indicators are intercalated into the grooves of double-helix DNA polymers, each of which produces an electrochemical signal within the applied potentials. Under optimum conditions, the SDA/HCR-based electrochemical aptasensor exhibits a high sensitivity for detection of Kana down to 36 fM with a linear range from 0.05 to 200 pM. Additionally, the as-prepared aptasensor is successfully employed to determinate the Kana in animal derived food (milk). With the advantages of high sensitivity, label-free strategy and excellent selectivity, the developed aptasensor possesses great potential application value in food-safety analysis field.


Assuntos
Aptâmeros de Nucleotídeos/química , Técnicas Eletroquímicas , Canamicina/análise , Leite/química , Técnicas de Amplificação de Ácido Nucleico , Animais , Bovinos
17.
Artigo em Inglês | MEDLINE | ID: mdl-30352014

RESUMO

This work presents a method of magnetic solid-phase extraction (MSPE) combined with high-performance liquid chromatography (HPLC) to analyse five synthetic azo dyes (tartrazine, amaranth, carmine, sunset yellow, allura red) in different food samples. The magnetic graphene oxide nanocomposite (GO@Fe3O4) was prepared by a one-step solvothermal method and used as the sorbent for extraction and pre-concentration of azo dyes in food samples. The as-prepared GO@Fe3O4 nanocomposite was characterised by transmission electron microscope, Fourier transform-infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, and Brunuer-Emmett-Teller analysis. The extraction and desorption parameters were investigated, including the material amount, extraction time, pH of the solution, desorption temperature, and desorption solvents. Under the optimised conditions, the limits of detection (LODs) were 1.14-2.23, 0.36-0.77 and 0.68-1.26 ng/g for candy, jelly, and plum candy, respectively. The limits of quantification (LOQs) were 4.02-7.73, 1.21-2.50 and 2.31-4.20 ng/g for candy, jelly, and plum candy, respectively. For the analysis of spiked jelly, recoveries were between 73.2% and 107.7%, with RSDs lower than 1.34 %. The developed method was successfully applied to the analysis of real samples including jelly, candy and plum candy.


Assuntos
Compostos Azo/análise , Análise de Alimentos , Contaminação de Alimentos/análise , Grafite/química , Nanopartículas de Magnetita/química , Óxidos/química , Adsorção , Cromatografia Líquida de Alta Pressão , Propriedades de Superfície
18.
J Chromatogr A ; 1570: 47-55, 2018 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-30078480

RESUMO

In this work, a novel nanoscale graphitic carbon nitride hybridized with copper oxide (nano-g-C3N4/CuO) composite was prepared and used as the coating of solid-phase microextraction (SPME) for the first time. The coating was applied to adsorption and preconcentration of polycyclic aromatic hydrocarbons (PAHs) including naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, and pyrene from water and soil prior to gas chromatography (GC) analysis. Compared with pristine nanoscale graphitic carbon nitride (nano-g-C3N4) or copper oxide (CuO), the as-prepared nano-g-C3N4/CuO composite as the coating of SPME provided the best adsorption affinity for PAHs. Moreover, the extraction efficiencies of the nano-g-C3N4/CuO coated fibers were much higher than that of bulk-g-C3N4/CuO hybrids. The developed method exhibited excellent linearity for target analytes in the range of 0.1-1000 ng/mL with determination coefficient (R2) not lower than 0.9944. The limits of detection (LODs) of the established method for the analysis of PAHs were achieved between 0.025 and 0.40 ng/mL. The relative standard deviations (RSDs) for three replicate extractions with one fiber were determined from 2.5% to 7.3%. The fiber-to-fiber reproducibility (n = 3) was 5.4-12.8%. The prepared coating also demonstrated excellent thermal and chemical stability. The method was successfully applied to analysis of target analytes in water and soil samples and the corresponding contents were calculated between 0.07 and 1.58 µg/g.


Assuntos
Cromatografia Gasosa/métodos , Cobre/química , Grafite/química , Nanocompostos/química , Nitrilas/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Microextração em Fase Sólida/métodos , Adsorção , Limite de Detecção , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/isolamento & purificação
19.
Biosens Bioelectron ; 117: 590-596, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-30005378

RESUMO

In this work, a new "signal-on" split-type photoelectrochemical (PEC) sensing platform for prostate-specific antigen (PSA) detection was successfully constructed using p-type Cu-doped Zn0.3Cd0.7S as the photosensitive semiconductor material and target-triggered rolling circle amplification (RCA) for signal amplification. The signal derived from Cu-doped Zn0.3Cd0.7S was amplified by hemin/G-quadruplex. Upon target PSA introduction, the aptamer-primer probe (apt-pri) was captured by capture antibody-conjugated magnetic bead (MB-mAb) to form the sandwiched MB-mAb/PSA/apt-pri. The complex could initiate the RCA reaction to produce a long single-stranded DNA that provided binding sites for G-rich DNA and to form long single-stranded DNA/G-quadruplex/hemin. Upon the addition of exonuclease III (Exo III), the hemin/G-quadruplex immobilized on the RCA long product could be released by the digestion of Exo III. The hemin/G-quadruplex complexes in this study were used as efficient electron acceptors to neutralize the photoelectrons generated from the semiconductor and hindered the recombination of charges, thus enhancing the photocurrent. Under the optimum conditions, the developed sensing system displayed a good analytical performance with a linear range of 0.05-40 ng mL-1 PSA and a detection limit of 16.3 pg mL-1. Furthermore, good selectivity, high anti-interference ability, satisfactory reproducibility, and good accuracy were also achieved. These prominent analytical properties revealed that our strategy might be a potential and reliable tool for the detection of PSA.


Assuntos
Técnicas Biossensoriais/métodos , Exodesoxirribonucleases/metabolismo , Técnicas de Amplificação de Ácido Nucleico , Antígeno Prostático Específico/análise , Biomarcadores/análise , Compostos de Cádmio/química , Cobre/química , Quadruplex G , Humanos , Limite de Detecção , Masculino , Neoplasias da Próstata/sangue , Neoplasias da Próstata/diagnóstico , Reprodutibilidade dos Testes , Óxido de Zinco/química
20.
Biosens Bioelectron ; 109: 70-74, 2018 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-29529510

RESUMO

A new photoluminescence (PL) enzyme immunoassay was designed for sensitive detection of aflatoxin B1 (AFB1) via an innovative enzyme substrate, 6-aza-2-thiothymine-stabilized gold nanocluster (AAT-AuNC) with L-arginine. The enzyme substrate with strong PL intensity was formed through supramolecular host-guest assembly between guanidine group of L-arginine and AAT capped on the surface of AuNC. Upon arginase introduction, the captured L-arginine was hydrolyzed into ornithine and urea, thus resulting in the decreasing PL intensity. Based on this principle, a novel competitive-type immunoreaction was first carried out on AFB1-bovine serum albumin (AFB1-BSA) conjugate-coated microplate, using arginase-labeled anti-AFB1 antibody as the competitor. Under the optimum conditions, the PL intensity increased with the increment of target AFB1, and allowed the detection of the analyte at concentrations as low as 3.2 pg mL-1 (ppt). Moreover, L-arginine-AAT-AuNC-based PL enzyme immunoassay afforded good reproducibility and acceptable specificity. In addition, the accuracy of this methodology, referring to commercial AFB1 ELISA kit, was evaluated to analyze naturally contaminated or spiked peanut samples, giving well-matched results between two methods, thus representing a useful scheme for practical application in quantitative monitoring of mycotoxins in foodstuff.


Assuntos
Aflatoxina B1/isolamento & purificação , Técnicas Biossensoriais , Nanopartículas Metálicas/química , Aflatoxina B1/química , Arachis/química , Arginina/química , Técnicas Imunoenzimáticas , Soroalbumina Bovina/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...