Fabrication And Study Of Performance Of Versicolorina Electrochemical Sensor Electrode Based On CNTs

Objective: Aflatoxins (AFs) are one group of the most potentially carcinogenic, teratogenicand genotoxic substances. AFs are found to be one of the predominant mycotoxins incontaminating food and feed. They are seriously harmful to humans, livestock and poultries.Among them afltoxin B1is the most toxic and commonly contaminant. VersicolorinA (Ver A) isan important precursor of AFB1biosynthetic pathway. And it is closely related to thebiosynthesis of AFB1. Previous investigation indicated that Ver A is a feasible predictivebioindicator for aflatoxins-contamination of storage-crops. Therefore, to establish a rapid,sensitive and easy method for Ver A detection is important. Electrochemical sensors have theadvantages of such as low cost, simple operation, rapid response, high sensitivity, withouttedious sample pre-treatment. The sensors are potentially developed to be real-time monitoring,miniaturize and portable. Thus, in this thesis, an electrochemical sensor for Ver A wasconstructed. And a sensor way of Ver A detection was set-up.Methods: Ver A standard was prepared from a mutant of Aspergillus parasiticus andidentified by mass spectrometry. The sensor was constructed by self-assembly technique.Cysteamine (CSm) and single-walled carbon nanotubes (SWCNTs) were assembled onto thegold electrode with step-by-step optimization. The surface of the constructed sensor was viewedwith atomic force microscopy. The processes of caroxylation SWCNTs and sensor’sconstructions were monitored by infrared spectroscopy, cyclic voltammetry and electrochemicalimpedance spectroscopy.Results:(1) Three-milligram of Ver A standard was obtained.(2)The optimized way to buildthe Ver A sensor was found to be SWCNTs/CSm/Au.(3)The final obtained Ver A sensor showedacceptable performances including of a wide linear range from100ppb to1200ppb, a detectionlimit of75ppb (3SD/slope), a sensitivity of0.30μA.ng-1.ml.cm-2with a good selectivity to thegeneral electroactive interferences. The presented Ver A electrochemical sensor had theadvantage of a good repeatability. Under same conditions, the RSD of12replicatedeterminations of400ppb Ver A was4.6%. Seven one-patch-made electrodes showed a4.2%ofRSD of350ppb Ver A detection. The Ver A-sensor was stable, it remained98.2%of the original current value after a30-day of storage at4℃. After a simple preparation of80%methanol extraction, the sensor-way of Ver A detection for standard samples (6corn-powders)had giving acceptable recovery values from95.5%to111.8%with RSD in the range of1.1%~6.2%.In conclusion: In this thesis, the assembling method of the Ver A sensor electrode wasestablished. The present sensor was easy to operate in Ver A detection, without the sophisticatedpreparation processes.