Application Of Sol-gel Based Imprinting Electrochemical Sensors For Food Safety Analysis

Imprinting membrane possesses the advantages of molecularlyimprinting technology and membrane separation technology with anaffinity and selectivity to a specific molecule. Due to its uniquesuperiority, it has been used in food sample preparation and foodcomposition analysis with a huge applied potential. Electrochemicalsensors, with the advantages of easy preparation, high sensitivity high, lowcost, and easy automation, have got widely attentions. By usingmolecularly imprinting membrane as the recognition element of sensors,an imprinting electrochemical sensor has a promising future. Base onelectropolymerization method and sol-gel technology, three kinds ofelectrochemical sensors were constructed in our work and used for foodsafety analysis, as follows:1. A sol-gel based electrochemical sensor was developed formelamine direct and selective detection in real samples. Thin film ofmolecularly imprinted sol-gel polymers with specific binding sites formelamine in acid solution was fabricated on glassy carbon electrodesurface by electropolymerization method. Oxidation peak of melamine waschosen as a detected signal for the properties study of the sensor. Underthe optimized conditions, the sensor displayed an excellent recognitioncapacity towards melamine compared with other structural similarmolecules. With acceptable regeneration and stability the sensor coulddetect melamine in the range of6.3×10-7~1.1×10-4mol L-1with a detectedlimit of6.8×10-8mol L-1(S/N=3). The result of real samples detectionindicated that the proposed low cost electrochemical sensor might bepotential to determine melamine in real samples to ensure food safety.2. A surface imprinting electrochemical sensor was prepared forselective recognition and detection of tert-butylhydroquinone withcarboxylized polystyrene microspheres as a sacrificial template byelectopolymerization method. Under the optimized conditions, the linearrange of the sensor to tert-butylhydroquinone was5.0×10-7~4.2×10-3molL-1with the limit of detection of3.4×10-7mol L-1(S/N=3). And the sensorexhibited specificity and selectivity towards template molecules as well asexcellent reproducibility, regeneration and stability. Furthermore, thesensor could be applied to determine tert-butylhydroquinone in complexsamples with a recovery of92.3%~108%. 3. A novel electrochemical sensor prepared by stepwise modifying ofgraphene-single walled carbon nanotubes composite and molecularlyimprinting polymers was developed for the determination of propyl gallate.Modified molecular imprinting polymers and the modifiedgraphene-single walled carbon nanotubes composite endowed the sensor agood selective recognition and sensitivity towards template molecules,respectively. Under the optimized conditions, the linear range of the sensorto propyl gallate was8.0×10-8~2.6×10-3mol L-1with the limit ofdetection of5.0×10-8mol L-1(S/N=3). With the advantages of easypreparation, excellent regeneration, and good stability, the sensor could beapplied to determine propyl gallate in complex samples with a satisfactoryresult.