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    Multiwalled carbon nanotubes modified two dimensional MXene with high antifouling property for sensitive detection of ochratoxin A
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    Abstract:
    Electrochemical sensor has great potential in the detection of small molecules by virtues of low cost, fast response, and easy to miniaturization. However, electrochemical sensing of ochratoxin A (OTA) was seriously hindered by the heavy electrode-fouling effect and poor electrochemical activity inherent from OTA molecular. Herein, two-dimensional titanium carbide (2D Ti3C2) MXene incorporated with carboxylic multiwalled carbon nanotubes (cMWCNTs) was developed as a glassy carbon electrode modifier for rapid and sensitive detection of OTA. Physical characterizations combined with electrochemical techniques revealed that cMWCNTs can not only prevent the restacking of 2D Ti3C2nanosheets but also facile its electron transfer, leading to a nanohybrid with a high specific surface and good electrocatalytic activity to OTA. Under optimal conditions, the electrochemical sensor showed a good linear response to OTA in a concentration range from 0.09 to 10μmol·l-1and a low detection limit (LOD) of 0.028μmol·l-1. The proposed sensor was impelled successive times to detect OTA, a good repeatability was obtained, indicating the constructed sensor possessed good anti-fouling property. Moreover, satisfactory recoveries between 91.8% and 103.2% were obtained in the real sample analysis of grape and beer, showing that the developed sensing technique is reliable for the screening of trace OTA in food resources.
    Keywords:
    Electrochemical gas sensor
    Repeatability
    Linear range
    Due to the strong oxidizing properties of H2O2, excessive discharge of H2O2 will cause great harm to the environment. Moreover, H2O2 is also an energetic material used as fuel, with specific attention given to its safety. Therefore, it is of great importance to explore and prepare good sensitive materials for the detection of H2O2 with a low detection limit and high selectivity. In this work, a kind of hydrogen peroxide electrochemical sensor has been fabricated. That is, polypyrrole (PPy) has been electropolymerized on the glass carbon electrode (GCE), and then Ag and Cu nanoparticles are modified together on the surface of polypyrrole by electrodeposition. SEM analysis shows that Cu and Ag nanoparticles are uniformly deposited on the surface of PPy. Electrochemical characterization results display that the sensor has a good response to H2O2 with two linear intervals. The first linear range is 0.1-1 mM (R2 = 0.9978, S = 265.06 μA/ (mM × cm2)), and the detection limit is 0.027 μM (S/N = 3). The second linear range is 1-35 mM (R2 = 0.9969, 445.78 μA/ (mM × cm2)), corresponding to 0.063 μM of detection limit (S/N = 3). The sensor reveals good reproducibility (σ = 2.104), repeatability (σ = 2.027), anti-interference, and stability. The recoveries of the electrode are 99.84-103.00% (for 0.1-1 mM of linear range) and 98.65-104.80% (for 1-35 mM linear range). Furthermore, the costs of the hydrogen peroxide electrochemical sensor proposed in this work are reduced largely by using non-precious metals without degradation of the sensing performance of H2O2. This study provides a facile way to develop nanocomposite electrochemical sensors.
    Polypyrrole
    Linear range
    Electrochemical gas sensor
    Bimetallic strip
    Oxidizing agent
    Citations (4)
    An Fe–N–C/AuNP nanohybrid was combined with a glassy carbon electrode to construct a novel electrochemical sensor for rapid detection of gallic acid (GA). The sensor exhibited excellent performance to detect GA with a wide linear response range and low detection limit.
    Electrochemical gas sensor
    Linear range
    Glassy carbon
    Citations (8)
    To evaluate the ochratoxin A risk in French vineyards, five winemaking regions were investigated. An exhaustive survey of the fungal microflora of 60 grape samples was carried out at two development stages of the berries: end of veraison and harvest time. Potentially toxinogenic fungi isolated from grapes were assessed in vitro for ochratoxin A production. Ochratoxin A was also quantified in musts by high-performance liquid chromatography after cleanup on immunoaffinity columns. Among the 90 species identified, almost half are listed as mycotoxin producers, but only 2 are potentially ochratoxinogenic: Aspergillus carbonarius and Aspergillus niger. Among these strains, only A. carbonarius, isolated from the Languedoc region at harvest time, was found to produce ochratoxin A. These results were in accordance with the presence of ochratoxin A in French southern region musts (0.01-0.43 microg/L) and confirmed the major implication of A. carbonarius in ochratoxin A contamination.
    Veraison
    Ochratoxins
    Ochratoxins
    Winemaking
    Aspergillus niger
    Food contaminant
    Citations (84)
    Conductivity measurements are important within the area of insulating material characterization especially for HVDC transmission application. Within first investigations a derived novel test setup showed promising results regarding overall reproducibility with regard to the test specimen production and test configurations. Based on these first results, the setup is subjected to further enhancements and used for a repeatability study focusing on measurement repeatability and robustness. With a detailed knowledge about the repeatability of obtained results any impact to the test specimen production and preparation can be determined. After a brief description of the experimantal setup a repeatability study in which two different test specimens are measured repetitively a deviation analysis is carried out. Furthermore as used materials are commercially available XLPE for AC and DC application a comparison of these materials is done whilst results are presented and discussed.
    Repeatability
    Robustness
    Citations (5)
    Variability introduced into numerical measurements by a measuring instrument is referred to as measurement instrument repeatability. Measurement instrument repeatability estimation methods exist when the measurements are repeatable. However, when measurements are destructive and repeated measurements are not possible, estimating measuring instrument repeatability is difficult since repeatability is confounded with, and usually cannot be separated from item variability. In this paper an estimator for destructive measuring instrument repeatability is obtained from measurements of two different item types, under the assumptions of constant item type measurement coefficient of variation, constant repeatability, and independent and normally distributed measurements. The estimator's variance is also derived, from which a confidence interval for repeatability can be computed. The results add to the body of existing methods that exploit some assumed pattern of item variability, or alternatively make other assumptions needed to estimate measurement instrument repeatability when repeated measurements are unavailable.
    Repeatability
    Coefficient of variation
    Accuracy and precision
    Variance components