Construction Of Novel Copper Ion And Iron Ion Electrochemical Sensors And Its Application In Food Analysis

Fast and sensitive electrochemical sensors have broad application prospects in the field of food quality and safety detection.Among many electrochemical sensors,In the field of electrochemical sensors,all-solid-state ion-selective electrodes and nucleic acid-modified electrodes have been widely used in the detection of heavy metals,pathogenic bacteria and antibiotics in food due to their fast response time,low detection limit,and small sample disturbance.In this paper,copper ions and iron ions as two kinds of heavy metals are used as detection objects,which are commonly found in food.Two new electrochemical sensor systems are established and successfully used for accurate,rapid and sensitive detection and analysis of corresponding targets in complex samples.The main content of the paper is as follows(1)Preparation and application of carbon nanotube all-solid-state copper ion-selective microelectrodes.The first part of the research work proposes a new all-solid-state ion-selective microelectrode with high mechanical strength,stability and simple operation,which was successfully used for the simple and rapid detection of copper ions,and the detection of copper ions in oyster hemolymph.Perform morphological analysis.The Methyl Methacrylate-Decyl Methacrylate(MMA-DMA)was used as the polymer film substrate,and the filling of the polymer film was controlled by a microinjection instrument,thereby improving the stability and reproducibility of the microsensor.Under the optimized conditions,the fabricated Cu²⁺-IS?E exhibited a Nernst response to Cu²⁺in ionized water in the range of 1×10^-8-1×10^-4M,and the detection limit was 2.8×10^-9M.Cu²⁺in the background of 0.5 M Na Cl exhibited a Nernst response in the range of 1×10^-7-1×10^-3M with a detection limit of 5.2×10^-8.At the same time,the prepared Cu²⁺-IS?E was used for the speciation analysis of copper(including total copper and free copper)in oyster hemolymph,and the results were basically consistent with the results measured by atomic absorption spectrometry.(2)Construction and application of a label-free nucleic acid-modified electrode for electrocatalytic detection of iron ions.In the second part of the research work of this paper,a label-free nucleic acid-modified electrode is proposed for electrocatalytic rapid and sensitive detection of ferric ions.First,dodecanethiol was used as the gold electrode blocking agent,and the label-free nucleic acid chain was modified on the surface of the gold electrode by self-assembly to prepare a label-free nucleic acid modified electrode.EDTA-Fe(III)was quantified according to the signal gain value through electrocatalytic reduction reaction with EDTA-Fe(III)by using thionine as a redox indicator by 1:1 pairing complexation of ferric iron with EDTA analyze.The effects of scanning speed,immobilization density of nucleic acid strands and p H on the electrocatalysis of nucleic acid modified electrodes were investigated by cyclic voltammetry.Experiments show that the labeled nucleic acid modified electrode can rapidly detect ferric ions,and can eliminate the interference of other heavy metal ions,with good selectivity and specificity.The detection performance of the sensor was analyzed under the optimal detection conditions.The detection range of ferric ions was 10?M-750?M and detection limit is2.5 u M.which can be used for the detection of actual iron-fortified soy sauce with good recovery rate.