Electrochemical Sensing System Based On Molecular Imprinted Technology For The Determination Of Ractopamine

Ractopamine (RCT), one of β2-adrenergic receptor agonists, is usedclinically as oxytocin inhibitant or bronchodilator. In addition, since RCTwould improve lean meat rate and promote growth, it is still illegally usedin animal feed in order to improve economic efficiency. Concerning thefacts that RCT residues posses potential hazards in animal food, EuropeUnion and Peopoe’s Republic of China has formally prohibited thesupplementation of RCT in animal feed. Thus, it is of great significence toestablish rapid and efficient detecting methodologies to monitor the abuseof RCT in feed industry. At present, the most common methods for thedetermination of RCT are chromatography and immunoassay. Thesemethods are accurate and sensitive techniques used for the confirmortaryquantitation. However, they are not suitable for fast and efficient on-sitetesting due to the complicated operation, long detecting time and highexpense. Furthermore, because there are still great needs for the detectionof RCT in great number of biological samples, it is very necessary to setup accurate, fast, simple and economic detecting method.In this study, based on the molecular imprinted technologies andelectrochemical sensing methodologies, two novel types ofelectrochemical sensing systems were established by using new transducermaterial on electrodes. The sensor performance was evaluated by thestudies on the superficial characteristics. The main content of theexperiments and results were described as follows:1. Preparation of ractopamine molecularly imprinted polymers andanalysis of its superficial characteristics. The optimal functional monomer(methacrylic acid) was selected using computer simulation techniques andmolecularly imprinted polymers (MIPs) of RCT were prepared using thermal polymerization in sealed tubes. The mechanism of the interactionand recognition between template and functional monomer was studied byInfrared spectrum. Moreover, the adsorption properties of RCT-MIPs werealso analysed and evaluated using ultraviolet spectrography. The resultsshowed that the MIPs posessed significant absorptional capacity towardsRCT and its average absorption rate reached83.4%. Thus, based on theabove premise, these MIPs were effectively used in the preparation ofmolecularly imprinted membrane (MIM) of RCT, which also showed thespecifically adsorptional ability towards the template. Then the MIM wasapplied as the sensing element in the fabrication of novel electrochemicalsensor for the determination of RCT.2. The establishment of the conductometric sensing method for thedetection of RCT based on molecular imprinted technology (MIT): Thescreen printed electrode (SPE) was firstly modified with7,7,8,8-Tetracyanoquinodimethane (TCNQ) and followed by thesynthesization of molecularly imprinted membrane (MIM) of RCT on themodified SPE by using in-situ thermal polymerization techniques. In thenext step, the MIM-TCNQ modified screen printed electrode wasconnected to a portable conducometer using USB port to set up theconductometric sensor for the detection of RCT in biological samples. Thesuccessive analysis and multiple determinations were carried out only bychanging the MIM-TCNQ modified screen printed electrode. The resultsindicated that this sensing methodology menifiested the favorable linearresponse of the sensing signal to the concentration of RCT over the rangeof0.2~1.0mg/L, with the detection limit of0.05mg/L and recovery of97.0%~99.3%. The lifespan of the modified SPE was more than4months.This sensing methodology showed the advantages of simple operation,high recovery and favorable stability, which can be effectively used in therapid determination of RCT on the sites.3. The establishment of the amperometric sensing methodology forthe detection of RCT based on molecular imprinted technology (MIT): The screen printed electrode (SPE) was firstly modified with multi-wall carbonnanotubes (MWCNs) and followed by the synthesization of molecularlyimprinted membrane (MIM) of RCT on the modified SPE by using in-situthermal polymerization techniques. In the next step, the MIM-MWCNsmodified screen printed electrode was connected to a portableamperometer using USB port to set up the amperometric sensor for thedetection of RCT in biological samples. The successive analysis andmultiple determinations were carried out only by changing theMIM-MWCNs modified screen printed electrode. The results indicatedthat this sensing methodology menifiested the favorable linear response ofthe sensing signal to the concentration of RCT over the range of0.04~0.24mg/L, with the detection limit of0.012mg/L and recovery of91.7%~97.8%. The detection time of this method was within5minutes.Furthermore, the lifespan of the modified SPE was more than6months.This sensing methodology showed the advantages of high sensitivity,satisfactory specificity, simple operation and low cost. In summary, thissensing system can be effectively used in the rapid determination of RCTon the sites.