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1.
Emerg Microbes Infect ; 13(1): 2301666, 2024 Dec.
Article in English | MEDLINE | ID: mdl-38163752

ABSTRACT

In the past few decades, several emerging/re-emerging mosquito-borne flaviviruses have resulted in disease outbreaks of public health concern in the tropics and subtropics. Due to cross-reactivities of antibodies recognizing the envelope protein of different flaviviruses, serosurveillance remains a challenge. Previously we reported that anti-premembrane (prM) antibody can discriminate between three flavivirus infections by Western blot analysis. In this study, we aimed to develop a serological assay that can discriminate infection or exposure with flaviviruses from four serocomplexes, including dengue (DENV), Zika (ZIKV), West Nile (WNV) and yellow fever (YFV) viruses, and explore its application for serosurveillance in flavivirus-endemic countries. We employed Western blot analysis including antigens of six flaviviruses (DENV1, 2 and 4, WNV, ZIKV and YFV) from four serocomplexes. We tested serum samples from YF-17D vaccinees, and from DENV, ZIKV and WNV panels that had been confirmed by RT-PCR or by neutralization assays. The overall sensitivity/specificity of anti-prM antibodies for DENV, ZIKV, WNV, and YFV infections/exposure were 91.7%/96.4%, 91.7%/99.2%, 88.9%/98.3%, and 91.3%/92.5%, respectively. When testing 48 samples from Brazil, we identified multiple flavivirus infections/exposure including DENV and ZIKV, DENV and YFV, and DENV, ZIKV and YFV. When testing 50 samples from the Philippines, we detected DENV, ZIKV, and DENV and ZIKV infections with a ZIKV seroprevalence rate of 10%, which was consistent with reports of low-level circulation of ZIKV in Asia. Together, these findings suggest that anti-prM antibody is a flavivirus serocomplex-specific marker and can be employed to delineate four flavivirus infections/exposure in regions where multiple flaviviruses co-circulate.


Subject(s)
Dengue Virus , Dengue , Flavivirus Infections , Flavivirus , Zika Virus Infection , Zika Virus , Animals , Flavivirus/genetics , Zika Virus Infection/diagnosis , Zika Virus Infection/epidemiology , Zika Virus/genetics , Dengue Virus/genetics , Seroepidemiologic Studies , Antibodies, Viral , Flavivirus Infections/diagnosis , Flavivirus Infections/epidemiology , Yellow fever virus , Cross Reactions
2.
medRxiv ; 2023 Sep 25.
Article in English | MEDLINE | ID: mdl-37808865

ABSTRACT

In the past few decades, several emerging/re-emerging mosquito-borne flaviviruses have resulted in disease outbreaks of public health concern in the tropics and subtropics. Due to cross-reactivities of antibodies recognizing the envelope protein of different flaviviruses, serosurveillance remains a challenge. Previously we reported that anti-premembrane (prM) antibody can discriminate between three flavivirus infections by Western blot analysis. In this study, we aimed to develop a serological assay that can discriminate infection or exposure with flaviviruses from four serocomplexes, including dengue (DENV), Zika (ZIKV), West Nile (WNV) and yellow fever (YFV) viruses, and explore its application for serosurveillance in flavivirus-endemic countries. We employed Western blot analysis including antigens of six flaviviruses (DENV1, 2 and 4, WNV, ZIKV and YFV) from four serocomplexes. We tested serum samples from YF-17D vaccinees, and from DENV, ZIKV and WNV panels that had been confirmed by RT-PCR or by neutralization assays. The overall sensitivity/specificity of anti-prM antibodies for DENV, ZIKV, WNV, and YFV infections/exposure were 91.7%/96.4%, 91.7%/99.2%, 88.9%/98.3%, and 91.3%/92.5%, respectively. When testing 48 samples from Brazil, we identified multiple flavivirus infections/exposure including DENV and ZIKV, DENV and YFV, and DENV, ZIKV and YFV. When testing 50 samples from the Philippines, we detected DENV, ZIKV, and DENV and ZIKV infections with a ZIKV seroprevalence rate of 10%, which was consistent with reports of low-level circulation of ZIKV in Asia. Together, these findings suggest that anti-prM antibody is a flavivirus serocomplex-specific marker and can be employed to delineate four flavivirus infections/exposure in regions where multiple flaviviruses co-circulate.

3.
EBioMedicine ; 94: 104723, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37487418

ABSTRACT

BACKGROUND: Dengue virus outbreaks are increasing in number and severity worldwide. Viral transmission is assumed to require a minimum time period of viral replication within the mosquito midgut. It is unknown if alternative transmission periods not requiring replication are possible. METHODS: We used a mouse model of dengue virus transmission to investigate the potential of mechanical transmission of dengue virus. We investigated minimal viral titres necessary for development of symptoms in bitten mice and used resulting parameters to inform a new model of dengue virus transmission within a susceptible population. FINDINGS: Naïve mice bitten by mosquitoes immediately after they took partial blood meals from dengue infected mice showed symptoms of dengue virus, followed by mortality. Incorporation of mechanical transmission into mathematical models of dengue virus transmission suggest that this supplemental transmission route could result in larger outbreaks which peak sooner. INTERPRETATION: The potential of dengue transmission routes independent of midgut viral replication has implications for vector control strategies that target mosquito lifespan and suggest the possibility of similar mechanical transmission routes in other disease-carrying mosquitoes. FUNDING: This study was funded by grants from the National Health Research Institutes, Taiwan (04D2-MMMOST02), the Human Frontier Science Program (RGP0033/2021), the National Institutes of Health (1R01AI143698-01A1, R01AI151004 and DP2AI152071) and the Ministry of Science and Technology, Taiwan (MOST104-2321-B-400-016).


Subject(s)
Aedes , Dengue Virus , Dengue , Humans , Animals , Mice , Dengue/epidemiology , Disease Outbreaks , Mosquito Vectors
4.
Zhen Ci Yan Jiu ; 48(5): 488-93, 2023 May 25.
Article in Chinese | MEDLINE | ID: mdl-37247863

ABSTRACT

OBJECTIVE: To observe the effects of moxibustion on the contents of leukotriene B4 (LTB4), interleukin-17 (IL-17), tumor necrosis factor-α (TNF-α) and matrix metalloproteinase -9 (MMP-9) in serum, and explore the protection mechanisms of moxibustion in the patients with rheumatoid arthritis (RA). METHODS: A total of 64 patients with RA were randomly divided into treatment group (n=31) and control group (n=33). The patients in the control group were treated with conventional medication for consecutive 5 weeks. Based on the treatment in the control group, the patients in the treatment group were treated with moxibustion at bilateral Shenshu (BL23), Zusanli (ST36) and Ashi points, 3 times a week, for consecutive 5 weeks. Separately, the visual analogue scale (VAS) score, morning stiffness score, the number of tender joints, the number of swollen joints, the score of the disease activity score of 28 joints (DAS28) were observed; the contents of rheumatoid factor (RF), erythrocyte sedimentation rate (ESR) and C-reative protein (CRP) in serum were determined by biochemical method; and the contents of LTB4, IL-17, TNF-α and MMP-9 in serum were detected by using ELISA before and after treatment in the patients of both groups. RESULTS: After treatment, VAS score, morning stiffness score, the number of tender joints, the number of swollen joints, DAS28 score, the contents of serum RF in both groups, and contents of serum CRP, ESR, LTB4, IL-17, TNF-α and MMP-9 in the treatment group were significantly reduced when compared with those before treatment (P<0.01, P<0.05). After treatment, VAS score, morning stiffness score, the number of tender joints, the number of swollen joints, DAS28 score, and the levels of LTB4, IL-17 and MMP-9 in serum were obviously lower in the treatment group when compared with the control group (P<0.01, P<0.05). In the treatment group, the changes before and after treatment in the levels of LTB4, IL-17 and TNF-α were positively correlated with that of MMP-9 (P<0.05, r>0). CONCLUSION: Moxibustion at BL23 and ST36 combined with conventional medication significantly relieves joint pain and reduce disease activity in RA patients, which may be related to the modulation of LTB4, IL-17 and MMP-9 by moxibustion.


Subject(s)
Arthritis, Rheumatoid , Moxibustion , Humans , Leukotriene B4 , Interleukin-17/genetics , Tumor Necrosis Factor-alpha/genetics , Matrix Metalloproteinase 9/genetics , Arthritis, Rheumatoid/genetics , Arthritis, Rheumatoid/therapy
5.
Small Methods ; 7(7): e2300280, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37086111

ABSTRACT

Ni-rich layered cathodes with ultrahigh nickel content (≥90%), for example LiNi0.9 Co0.1 O2 (NC0.9), are promising for next-generation high-energy Li-ion batteries (LIBs), but face stability issues related to structural degradation and side reactions during the electrochemical process. Here, surface modulation is demonstrated by integrating a Li+ -conductive nanocoating and gradient lattice doping to stabilize the active cathode efficiently for extended cycles. Briefly, a wet-chemistry process is developed to deposit uniform ZrO(OH)2 nanoshells around Ni0.905 Co0.095 (OH)2 (NC0.9-OH) hydroxide precursors, followed by high temperature lithiation to create reinforced products featuring Zr doping in the crust lattice decorated with Li2 ZrO3 nanoparticles on the surface. It is identified that the Zr4+ infiltration reconstructed the surface lattice into favorable characters such as Li+ deficiency and Ni3+ reduction, which are effective to combat side reactions and suppress phase degradation and crack formation. This surface control is able to achieve an optimized balance between surface stabilization and charge transfer, resulting in an extraordinary capacity retention of 96.6% after 100 cycles at 1 C and an excellent rate capability of 148.8 mA h g-1 at 10 C. This study highlights the critical importance of integrated surface modulation for high stability of cathode materials in next-generation LIBs.

6.
Opt Lett ; 48(4): 964-967, 2023 Feb 15.
Article in English | MEDLINE | ID: mdl-36790986

ABSTRACT

In this work, an electro-optical polymer modulator with double-layered gold nanostrips, a polymer nanograting, and a metal substrate is proposed and designed. Interestingly, mode hybridization between the Fabry-Pérot (F-P) and anti-bonding modes is formed, and strongly depends on the nanograting size, which can be controllably modulated by an injection current. The simulation and calculation results show that the temperature sensitivity and large structural sensitivity for the polymer modulator could remain constant during the current-tuning process, and a near-zero reflectance and a low linewidth of 13.8 nm in the red region corresponding to a high quality (Q) factor of 51 is achieved. In addition, a large redshift of 60.7 nm and a super-high modulation depth of 424 are obtained at only 8 µA.

7.
Biomed Chromatogr ; 35(7): e5109, 2021 Jul.
Article in English | MEDLINE | ID: mdl-33660332

ABSTRACT

As a new molecular recognition element, oligonucleotide aptamer not only has higher affinity and specificity to target molecules, but also has the advantages of wide recognition range, in vitro synthesis and chemical stability compared with conventional antibodies. Since a kind of screening method termed systematic evolution of ligands by exponential enrichment (SELEX) was reported, scientists have extensively researched the methodology of how to highly and efficiently screen out aptamers from a library consisting of a large number of random oligonucleotides. Certainly capillary electrophoresis-based screening methodologies, including nonequilibrium capillary electrophoresis of equilibrium mixtures, equilibrium capillary electrophoresis of equilibrium mixtures, non-SELEX, ideal-filter capillary electrophoresis, capillary transient isotachophoresis, etc., are revolutionary. Compared with conventional SELEX, these capillary electrophoresis-based methodologies show incomparable advantages such as the single-round screening of aptamers and increased successful screening rate. Methodology studies on the screening process of aptamers are comprehensively reviewed.


Subject(s)
Aptamers, Nucleotide , Electrophoresis, Capillary , Oligonucleotides , Animals , Aptamers, Nucleotide/analysis , Aptamers, Nucleotide/chemistry , Humans , Mice , Oligonucleotides/analysis , Oligonucleotides/chemistry , SELEX Aptamer Technique
8.
Biomed Chromatogr ; 33(10): e4630, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31243785

ABSTRACT

A new capillary electrophoresis method was developed to study the synergistic effect of superoxide dismutase and jujuboside A or B on scavenging superoxide anion radical in serum matrix respectively, in which superoxide anion radical was generated from pyrogallol autoxidation. The electrophoresis conditions, and the factors affecting the productive rate of purpurogallin, such as pyrogallol autoxidation product and the activity of superoxide dismutase, were optimized. Under optimal conditions, the content of superoxide dismutase in Gibco newborn calf serum was 7.06 mg/L, RSD was 2.01% and the average recovery was 98.4%. The values of IC50 for jujuboside A and B in the serum matrix were 157.67 and 31.60 mg/L respectively, and they both had synergy on scavenging superoxide anion radical with superoxide dismutase, but there was no the dose-dependency on this synergy.


Subject(s)
Electrophoresis, Capillary/methods , Saponins/pharmacology , Superoxide Dismutase/pharmacology , Superoxides , Anions/analysis , Anions/metabolism , Drug Synergism , Free Radical Scavengers/pharmacology , Linear Models , Pyrogallol/analysis , Pyrogallol/chemistry , Pyrogallol/metabolism , Reproducibility of Results , Superoxides/analysis , Superoxides/metabolism
9.
J Agric Food Chem ; 66(6): 1307-1319, 2018 Feb 14.
Article in English | MEDLINE | ID: mdl-29378133

ABSTRACT

The pesticide and veterinary drug residues brought by large-scale agricultural production have become one of the issues in the fields of food safety and environmental ecological security. It is necessary to develop the rapid, sensitive, qualitative and quantitative methodology for the detection of pesticide and veterinary drug residues. As one of the achievements of nanoscience, quantum dots (QDs) have been widely used in the detection of pesticide and veterinary drug residues. In these methodology studies, the used QD-signal styles include fluorescence, chemiluminescence, electrochemical luminescence, photoelectrochemistry, etc. QDs can also be assembled into sensors with different materials, such as QD-enzyme, QD-antibody, QD-aptamer, and QD-molecularly imprinted polymer sensors, etc. Plenty of study achievements in the field of detection of pesticide and veterinary drug residues have been obtained from the different combinations among these signals and sensors. They are summarized in this paper to provide a reference for the QD application in the detection of pesticide and veterinary drug residues.


Subject(s)
Biosensing Techniques/methods , Drug Residues/analysis , Nanotechnology/methods , Pesticides/analysis , Quantum Dots/chemistry , Veterinary Drugs/analysis , Animals , Biosensing Techniques/instrumentation , Humans , Nanotechnology/instrumentation
10.
Pharmacogn Mag ; 13(51): 446-453, 2017.
Article in English | MEDLINE | ID: mdl-28839370

ABSTRACT

BACKGROUND: Rattan tea is a medicinal plant that has been used for many years for the treatment of inflammation, fatty liver, tumor, diabetes, and hyperlipidemia. OBJECTIVE: A green and novel approach based on surfactant-mediated, ultrasonic-assisted extraction (SM-UAE) was developed for the extraction of antioxidant polyphenols from Rattan tea. A nonionic surfactant Tween-80 was selected as extraction solvent. The antioxidant activity was measured by total phenolic content (TPC) and ferric-reducing/antioxidant capacity (FRAC) assay. MATERIALS AND METHODS: Optimization of extraction parameters including concentration of solvent, ultrasonic time, and temperature were investigated by response surface methodology. The antioxidant activity was measured by TPC and FRAC assay. RESULTS: The optimal extraction conditions were determined as 6.8% (v/v) of aqueous Tween-80, ultrasonic temperature of 54°C, and ultrasonic time of 28.8 min. Under these conditions, the highest TPC value of 360.4 mg gallic acid equivalent per gram of dry weight material (GAE/g DW) was recorded. Moreover, 6.8% (v/v) of aqueous Tween-80, ultrasonic temperature of 54.5°C, and ultrasonic time of 28.4 min were determined for the highest FRAC value of 478.2 µmol of Fe2+/g of weight material (µmol Fe2+/g DW). Compared with other methods, the TPC and FRAC values of 313.5 mg GAE/g DW and 389.6 µmol Fe2+/g DW were obtained by heat reflux extraction using ethanol as solvent, respectively, and 343.2 mg GAE/g DW and 450.1 µmol Fe2+/g DW were obtained by UAE using ethanol as solvent, respectively. CONCLUSION: The application of SM-UAE markedly decreased extraction time or extraction cost and improved the extraction efficiency, compared with the other methods. SUMMARY: Surfactant-mediated ultrasonic-assisted extraction of antioxidant polyphenols from Rattan TeaResponse surface methodology used to optimize parameters and study combined effectsOptimized surfactant-mediated ultrasonic-assisted extraction process enhances the antioxidant phenolics extraction in less time. Abbreviations used: SM-UAE: Surfactant-mediated ultrasonic-assisted extraction; TPC: total phenolic content; FRAC: Ferric reducing antioxidant capacity; RSM: Response surface methodology; BBD: Box-Behnken design.

11.
Electrophoresis ; 38(16): 2004-2010, 2017 08.
Article in English | MEDLINE | ID: mdl-28497571

ABSTRACT

A nonaqueous micellar electrokinetic capillary chromatography method with indirect LIF was developed for the determination of strobilurin fungicide residues in fruits and vegetables. Hydrophobic CdTe quantum dots (QDs) synthesized in aqueous phase were used as background fluorescent substance. The BGE solution, QD concentration, and separation voltage were optimized to obtain the best separation efficiency and the highest signal intensity. The optimal BGE solution consists of 40 mM phosphate, 120 mM sodium dodecyl sulfate, 15% v/v water and 15% v/v hydrophobic CdTe QDs in formamide, of which apparent pH is 9.5. The optimized separation voltage is controlled as 25 kV. The resultant detection limits of azoxystrobin, kresoxim-methyl, and pyraclostrobin are all 0.001 mg/kg, their linear dynamic ranges are 0.005-2.5 mg/kg, and the recoveries of the spiked samples are 81.7-96.1%, 86.5-95.7%, and 87.3-97.4%, respectively. This method has been proved to be sensitive enough to detect the aforementioned fungicides in fruits and vegetables at the maximum residue limits.


Subject(s)
Fruit/chemistry , Fungicides, Industrial/analysis , Methacrylates/analysis , Vegetables/chemistry , Chromatography, Micellar Electrokinetic Capillary/methods , Humans , Hydrophobic and Hydrophilic Interactions , Lasers , Limit of Detection , Pesticide Residues/analysis , Pyrimidines/analysis , Quantum Dots , Spectrometry, Fluorescence/methods , Strobilurins/analysis
12.
J Agric Food Chem ; 64(17): 3456-61, 2016 May 04.
Article in English | MEDLINE | ID: mdl-27088652

ABSTRACT

A new micellar electrokinetic chromatography method with large-volume sample stacking and polarity switching was developed to analyze amoxicllin, cephalexin, oxacillin, penicillin G, cefazolin, and cefoperazone in milk and egg. The important parameters influencing separation and enrichment factors were optimized. The optimized running buffer consisted of 10 mM phosphate and 22 mM SDS at pH 6.7. The sample size was 1.47 kPa × 690 s, the reverse voltage was 20 kV, and the electric current recovery was 95%. Under these optimum conditions, the enrichment factors of six ß-lactams were 193-601. Their LODs were <0.26 ng/g, and LOQs were all 2 ng/g, which was only 1/50-1/2 of the maximum residual limits demanded by U.S. and Japanese regulations. The intraday and interday RSDs of method were lower than 3.70 and 3.91%, respectively. The method can be applied to determine these six antibiotic residues in egg and milk.


Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Drug Residues/analysis , Milk/chemistry , Ovum/chemistry , beta-Lactams/analysis , Animals , Chromatography, High Pressure Liquid
13.
Anal Chem ; 86(14): 6843-9, 2014 Jul 15.
Article in English | MEDLINE | ID: mdl-24932699

ABSTRACT

An on-field colorimetric sensing strategy employing gold nanoparticles (AuNPs) and a paper-based analytical platform was investigated for mercury ion (Hg(2+)) detection at water sources. By utilizing thymine-Hg(2+)-thymine (T-Hg(2+)-T) coordination chemistry, label-free detection oligonucleotide sequences were attached to unmodified gold nanoparticles to provide rapid mercury ion sensing without complicated and time-consuming thiolated or other costly labeled probe preparation processes. Not only is this strategy's sensing mechanism specific toward Hg(2+), rather than other metal ions, but also the conformational change in the detection oligonucleotide sequences introduces different degrees of AuNP aggregation that causes the color of AuNPs to exhibit a mixture variance. To eliminate the use of sophisticated equipment and minimize the power requirement for data analysis and transmission, the color variance of multiple detection results were transferred and concentrated on cellulose-based paper analytical devices, and the data were subsequently transmitted for the readout and storage of results using cloud computing via a smartphone. As a result, a detection limit of 50 nM for Hg(2+) spiked pond and river water could be achieved. Furthermore, multiple tests could be performed simultaneously with a 40 min turnaround time. These results suggest that the proposed platform possesses the capability for sensitive and high-throughput on-site mercury pollution monitoring in resource-constrained settings.


Subject(s)
Colorimetry/methods , Mercury/analysis , Metal Nanoparticles/chemistry , Cell Phone , Colorimetry/instrumentation , DNA, Single-Stranded , Gold/chemistry , Limit of Detection , Microfluidic Analytical Techniques , Paper , Rivers , Thymine/chemistry , Water/analysis , Water/chemistry , Water Pollutants, Chemical/analysis
14.
Anal Bioanal Chem ; 406(13): 3201-8, 2014 May.
Article in English | MEDLINE | ID: mdl-24633513

ABSTRACT

A new assay was developed for the determination of five quinolone antibiotic residues in foods, loxacin, enrofloxacin, ciprofloxacin, lomefloxacin, and norfloxacin, by micellar electrokinetic capillary chromatography with indirect laser-induced fluorescence, in which cadmium telluride quantum dots were used as a fluorescent background substance. Some factors that affected the peak height and the resolution were examined. The optimized running buffer was composed of 20 mM SDS, 7.2 mg/L quantum dots, and 10 mM borate at pH 8.8. The separation voltage was 20 kV. Under these conditions, five quinolone antibiotic residues were separated successfully within 8 min. The detection limits ranged from 0.003 to 0.008 mg/kg; the linear dynamic ranges were all 0.01 ∼ 10 mg/kg; and the average recoveries of the spiked samples were 81.4 ∼ 94.6 %. The assay can meet the requirement of maximum residue limits to these five quinolone antibiotics in the regulations of the European Union and Japan and has been applied for determining their residues in animal-derived food.


Subject(s)
Animal Feed/analysis , Anti-Bacterial Agents/analysis , Cadmium Compounds/chemistry , Chromatography, Micellar Electrokinetic Capillary/methods , Lasers , Quantum Dots , Quinolones/analysis , Tellurium/chemistry , Animals , Ciprofloxacin/analysis , Enrofloxacin , European Union , Fluorescence , Fluoroquinolones/analysis , Hydrogen-Ion Concentration , Japan , Limit of Detection , Loxapine/analysis , Norfloxacin/analysis , Spectrometry, Fluorescence
15.
J Chromatogr Sci ; 52(2): 157-63, 2014 Feb.
Article in English | MEDLINE | ID: mdl-23390023

ABSTRACT

A new assay of micellar electrokinetic capillary chromatography with sweeping was developed to determine azoxystrobin, kresoxim-methyl and pyraclostrobin in fruits and vegetables. The key factors affecting resolution and peak height were studied and the optimum conditions were obtained for separation and enrichment. The running buffer consisted of 40 mM borate, 25 mM sodium dodecyl sulfate and 15% acetonitrile, and its pH was adjusted to 8.4. The sample was injected for 677 nL and the separation voltage was 25 kV. Under the optimum conditions, the enrichment factors of azoxystrobin, kresoxim-methyl and pyraclostrobin were 861, 550 and 403; the linear dynamic ranges were all 0.01-5.0 mg/L; the limits of detection were 0.002, 0.001 and 0.002 mg/kg; the recoveries of spiked samples were 85.1-98.5%, 87.5-97.0% and 89.1-99.1%, respectively. The assay can meet the requirement of maximum residue limits for these three strobilurin fungicides, and has been applied for determining their residues in fruits and vegetables.


Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Fruit/chemistry , Fungicides, Industrial/analysis , Pesticide Residues/analysis , Vegetables/chemistry , Acetonitriles , Carbamates/analysis , Hydrogen-Ion Concentration , Limit of Detection , Methacrylates/analysis , Phenylacetates/analysis , Pyrazoles/analysis , Pyrimidines/analysis , Reproducibility of Results , Strobilurins
16.
Food Chem ; 145: 41-8, 2014 Feb 15.
Article in English | MEDLINE | ID: mdl-24128447

ABSTRACT

A new method was developed for the determination of eight triazine herbicide residues in cereal and vegetable samples by on-line sweeping technique in micellar electrokinetic capillary chromatography (MEKC). Some factors affecting analyte enrichment and separation efficiency were examined. The optimum buffer was composed of 25 mM borate, 15 mM phosphate, 40 mM sodium dodecylsulfate (SDS) and 3% (v/v) of 1-propanol at pH 6.5. The separation voltage was 20 kV and the sample was injected at 0.5 psi for 240 s. The detection wavelength was set at 220 nm with the capillary temperature being at 25 °C. Under the optimized conditions, the enrichment factors were achieved from 479 to 610. The limits of detection (LODs, S/N = 3) ranged from 0.02 to 0.04 ng/g and the limits of quantification (LOQs) of eight triazine herbicides were all 0.1 ng/g. The average recoveries of spiked samples were 82.8-96.8%. This method has been successfully applied to the determination of the triazine herbicide residues in cereal and vegetable samples.


Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Edible Grain/chemistry , Herbicides/analysis , Pesticide Residues/analysis , Triazines/analysis , Vegetables/chemistry , Hydrogen-Ion Concentration , Limit of Detection
17.
J Chem Phys ; 139(22): 224111, 2013 Dec 14.
Article in English | MEDLINE | ID: mdl-24329060

ABSTRACT

Basing on the earlier works on the hierarchical equations of motion for quantum transport, we present in this paper a first principles scheme for time-dependent quantum transport by combining time-dependent density functional theory (TDDFT) and Keldysh's non-equilibrium Green's function formalism. This scheme is beyond the wide band limit approximation and is directly applicable to the case of non-orthogonal basis without the need of basis transformation. The overlap between the basis in the lead and the device region is treated properly by including it in the self-energy and it can be shown that this approach is equivalent to a lead-device orthogonalization. This scheme has been implemented at both TDDFT and density functional tight-binding level. Simulation results are presented to demonstrate our method and comparison with wide band limit approximation is made. Finally, the sparsity of the matrices and computational complexity of this method are analyzed.

18.
J Chromatogr Sci ; 51(7): 608-18, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23537564

ABSTRACT

The molecular imprinting technique is a highly predeterminative recognition technology. Molecularly imprinted polymers (MIPs) can be applied to the cleanup and preconcentration of analytes as the selective adsorbent of solid-phase extraction (SPE). In recent years, a new type of SPE has formed, molecularly imprinted polymer solid-phase extraction (MISPE), and has been widely applied to the extraction of agrochemicals. In this review, the mechanism of the molecular imprinting technique and the methodology of MIP preparations are explained. The extraction modes of MISPE, including offline and online, are discussed, and the applications of MISPE in the analysis of agrochemicals such as herbicides, fungicides and insecticides are summarized. It is concluded that MISPE is a powerful tool to selectively isolate agrochemicals from real samples with higher extraction and cleanup efficiency than commercial SPE and that it has great potential for broad applications.


Subject(s)
Agrochemicals/isolation & purification , Polymers/chemistry , Solid Phase Extraction/methods , Agrochemicals/chemistry , Molecular Imprinting , Polymers/chemical synthesis , Solid Phase Extraction/instrumentation
19.
Electrophoresis ; 34(9-10): 1304-11, 2013 May.
Article in English | MEDLINE | ID: mdl-23436573

ABSTRACT

A new MEKC method with large-volume sample stacking and polarity switching was developed for on-line preconcentration and detection of sulfonylurea herbicide (SUH) residues in cereals, including nicosulfuron (NS), thifensulfuon (methyl) (TFM), tribenuron-methly (TBM), sulfometuron-methyl (SMM), pyrazosulfuron-ethyl (PSE), and chlorimuron-ethyl (CME). In order to achieve a high resolution and enrichment factor, several parameters were optimized, such as the pH of the running buffer, the concentration of the BGE and the SDS, the separate voltage, the sample size, the pH, and the electrolyte concentration of the sample. The optimal running buffer was composed of 30 mM borate and 80 mM SDS at pH 7.0. The borate concentration in the sample was 30 mM and the pH value of the sample was the same as that of the running buffer. The concentrating voltage and the separating voltage were -15 kV and 15 kV, respectively. The sample size was 1.455 kPa × 780 s (33.11 cm). Under the optimum conditions, for NS, TFM, TBM, SMM, PSE, and CME, the enrichment factors were 613, 642, 835, 570, 709, and 599; the LODs were 0.29-0.50 ng/g, 0.22-0.36 ng/g, 0.60-0.89 ng/g, 0.39-0.72 ng/g, 0.28-0.56 ng/g, and 0.31-0.57 ng/g; the LOQs of six SUHs were all 5 ng/g; the average recoveries of the spiked sample were 86.68-92.99%, 80.73-93.65%, 81.49-94.40%, 82.97-95.1%, 82.96-98.84%, and 80.41-92.94%, respectively.


Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Edible Grain/chemistry , Herbicides/isolation & purification , Sulfonylurea Compounds/isolation & purification , Buffers , Herbicides/analysis , Hydrogen-Ion Concentration , Limit of Detection , Sulfonylurea Compounds/analysis
20.
Sci Technol Adv Mater ; 14(4): 044403, 2013 Aug.
Article in English | MEDLINE | ID: mdl-27877588

ABSTRACT

A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody-antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml-1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.

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