Electrochemical Detection Of Vitamin B12,mercury Ions And Rutin Based On Fenton-type Reaction

This thesis introduces the classification and application of electrochemical sensors and the polymer-modified electrodes.The development history and application prospect of Fenton-type reaction is summarized.Poly?thionine??PTH?and two kinds of carbon based nanomaterials were used to construct several electrochemical sensors.The quantitative detections of vitamin B12(V_B12),mercury ions(Hg²⁺)and rutin?Vp?were performed based on Fenton-type reaction.The main works are listed as follows:1.The glassy carbon electrode?GCE?modified with poly?thionine?was prepared by using a two-step polymerization method.Cu²⁺-involved Fenton-type reaction could produce hydroxyl radicals which oxidized PTH effectively.Cobalt ions were liberated from V_B12 in the presence of hydrogen peroxide.Copper ions in the solution reacted with the released ligands from V_B12 molecules,which inhibited the Fenton-type reaction to a certain extent,resulting in the decrease of the cathodic peak current of PTH during cyclic voltammetric scan?CV scan?.The current change of the developed sensor exhibited a good linear response to the V_B12concentration in the range of 10 nM-100?M.The detection limit of 2 nM was obtained at a signal-to-noise ratio of 3.The proposed electrochemical sensor was used to detect V_B12 in actual samples and the recovery rate was found to vary from 92%to 102%.It provides an efficient method for rapid and simple detection of V_B12.2.The GCE modified with PTH and amino-functionalized graphene quantum dots?af-GQDs?was fabricated by using the CV scan.H₂O₂displayed a weak oxidation ability to the dye polymer on the electrode surface on near-neutral condition.Copper ions and mercury ions could catalyze the reduction of H₂O₂,and the catalytic ability of the former was better than that of the latter under the same conditions.The coordination reaction between thiourea and Cu²⁺inhibited the Cu²⁺-involved Fenton-type reaction to a certain degree,which significantly reduced the cathodic peak current of PTH.Hg²⁺could exchange with Cu²⁺in the Cu²⁺-thiourea complex.Copper ions were set free and the Fenton-type reaction was recovered.As a result,the cathodic peak current of the dye polymer increased correspondingly.A sensitive,selective and indirect detection method for trace Hg²⁺was developed.The proposed sensor exhibited a good linear response to Hg²⁺in the concentration range of 1pM-1?M.The detection limit reached 0.98 pM at a signal-to-noise ratio of 3.This method has been successfully applied for the detection of mercury ions in actual water samples,and the recovery rate varied from97%to 103%.3.The double-layer structure composite composed of multi-wall carbon nanotubes?MWCNT?and PTH was assembled on GCE surface by using a two-step method comprising drip-drying and electropolymerization.The composite showed a stable property and a good electroconductivity.The coordination reaction between rutin and copper ions promoted the Fenton-type reaction and produced more hydroxyl radicals,leading to the increase of the cathodic peak current of PTH.Rutin at low concention in the range of 10 pM-1?M was detected by using this sensitive and selective electrochemical sensor.The content of rutin in tablets was successfully measured and the results were satisfactory.