Preparation Of Electrochemical Sensors And Applications For Detecting Folic Acid And Melamine

This article mainly introduced the type and the preparation methods of electrochemical sensors,and then described their applications in the field of analytical chemistry. Meanwhile a series of the goodperformance of electrochemical sensors of folic acid and melamine were prepared, which provided newfeasible methods for determination of folic acid and melamine. The main research work was as follows:1. Determination of Folic Acid by Glassy Carbon Electrode modified with poly-Methylene blue andmulti-walled carbon nanotubesThe glassy carbon electrode modified with Poly-Methylene blue and multi-walled carbonnanotubes (PMB/MWCNTs/GC) was prepared by electropolymerization method. The electrode exhibitedgood electrocatalytic activity for folic acid. The experiments results showed that the reduction peakcurrent at-0.51V was linear with the concentration of folic acid over the range of3.4×10-6~1.1×10-4mol/L, with a detection limit of1.6×10-6mol/L in the best experimental conditions. Test for recovery wascarried out by standard addition method, and values of recovery ratio were in the range of90.8%~101.0%. The modified electrode was prepared simply and had good stability.2. Determination of Folic Acid by Composite Film Modified Electrode Modified with Poly-Alizarin Redand Multi-walled Carbon NanotubesThe novel modified electrode was fabricated by electropolymerizing alizarin red onto thesurface of Multi-walled carbon nanotubes on glassy carbon electrode surface, which exhibited goodelectrocatalytic activity for folic acid. The experiments results showed that the reduction peak current offolic acid at-0.63V was linear with its concentration over the range of1.25×10-6~4.00×10-5mol/L in the best experimental conditions (R=0.9985). Test for recovery was carried out by standard addition method,and the recovery ratios were in the range of92.0%~102.0%. The modified electrode was prepared simplywith excellent stability, which provides a new feasible method for determination of folic acid.3. Ultrastable Method for Determination of Folic Acid Based on Poly-Neutral Red and Multi-walledCarbon Nanotubes Composite Nano-filmUsing electrocatalytic property of nanomaterials and molecular recognition characterstic ofneutral red (NR), a new modified electrode was fabricated by electropolymerizing NR onto the surface ofMulti-walled carbon nanotubes modified glassy carbon electrode, which exhibited good electrocatalyticactivity for folic acid. The experiments results showed that a good linear relationship between thereductive peak current of folic acid and its concentration was in the range6.25×10-7~5.00×10-5mol/Lwith a detection limit of1.37×10-7mol/L in the optimal conditions. The recovery ratio was in the rangeof99.3%~103.2%. The composite film modified electrode exhibited excellent stability with simplefabrication, which established solid foundation for practical applications.4. Determination of Folic Acid by Glassy Garbon Electrode modified with poly-Crystal VioletThe novel modified electrode was fabricated by electropolymerizing Crystal Violet onto thesurface of glassy carbon electrode surface, which exhibited good electrocatalytic activity for folic acid.The experiments results showed that the reduction peak current of folic acid at-0.65V was linear with itsconcentration over the range of1.00×10-5~7.00×10-5mol/L in the best experimental conditions(R=0.9963). Test for recovery was carried out by standard addition method, and the recovery ratios werein the range of90.4%~101.0%. The modified electrode was prepared simply with excellent stability,which provides a new feasible method for determination of folic acid.5. Electrochemical sensor based on Multi-walled carbon nanotubes/Gold nanoparticles composite for determination of melamineA new electrochemical sensor was prepared firstly based on Multi-walled carbonnanotubes/Gold nanoparticles and Nafion composite film immobilized on glassy carbon electrode, whichshowed an excellent electrocatalytic activity for oxidation of melamine. Under optimal conditions, theoxidation peak current was found to be linearly related to melamine concentration over the range of3.9×10-6to4.0×10-3mol/L with a detection limit of1.9×10-6mol/L, and the recovery ratio was94.6%~101.0%. This method for determination of melamine exhibited good stability, reproducibility andwith easy preparation, which showed potential applications for practice.