Study On Rapid Detection Of Vitamin C Based On The Electrochemical Method

Vitamin C(ascorbic acid,Vc),is an indispensable biological factor in maintaining the body's normal life activities.It participates in many biological effects in the body,including promoting the synthesis of collagen,synthesising of neurotransmitter,hydroxyl of steroids and organic substance.The balanced amount of Vc helps to satisfy the needing of human body,enhance the function of human body to fight disease and reduce the incidence of cancer.Being lack of Vc or ingesting Vc too much will make adverse effects on human body.At the same time,the change of Vc content can be used to evaluate the freshness and storage resistance of fruits and vegetables.Moreover,Vc is widely used as antioxidant in industry.Therefore,It is of great significance to establish a quick and efficient detecting method for Vc.Based on the principle of that Vc can be oxidated directly at the surface of electrode,this article introduced electrochemical methods to detect Vc in food.The main contents got listed as follows:1.Electrodes selection: glassy carbon electrode(GCE),homemade platinum wire microelectrode(ME)and embedded powder microelectrode(PME)were introduced as working electrodes.The functional nanomaterials multi-walled carbon nanotubes(MWCNTs)made through mixed acid phase oxidation which had excellent electrical conductivity was introduced to enhance the detection performance of working electrodes.Dispersants including H2 O and N,N-dimethyl formamide(DMF)were applied to fabricate modified electrodes including water/MWCNTs/GCE,DMF/MWCNTs/GCE,DMF/carboxyl/MWCNTs/GCE,water/MWCNTs/ME,DMF/MWCNTs/ME,DMF/carboxyl/MWCNTs/ME.Then the optimized DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME were chosen out through different characterization methods.Based on former conclusions,carboxyl/MWCNTs/PME got fabricated through ME was corroded by aqua regia and embedded with carbon MWCNTs in sequence.2.Optimizing of the detection condition: DMF/carboxyl/MWCNTs/GCE and DMF/carboxyl/MWCNTs/ME were used as working electrodes and the optimal modification concentration was confirmed at 1.0×10-3 g/mL.Meanwhile,the optimal pH value for three categories of electrodes were confirmed as 7.0,5.0 and 6.0 by cyclic voltammetry respectively.Through exploring Vc's action on the surface of three categories of electrodes,it was found that Vc's oxidation on DMF/carboxyl/MWCNTs/GCE and DMF/carboxyl/MWCNTs/ME were controlled by adsorption,and Vc's oxidation on carboxyl/MWCNTs/PME was controlled by diffusion.3.Based on the above inquiry,the DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME and carboxyl/MWCNTs/PME were used as working electrodes.When DMF/carboxyl/MWCNTs/ME and carboxyl/MWCNTs/PME were applied to detect Vc,three electrodes system could be simplified as two electrodes system.Based on DMF/carboxyl/MWCNTs/GCE,the linear equations were Ipa(10-5 A)=0.226c(10-4 mol/L)+1.351 with linear range: 1.0×10-6~1.0×10-3 mol/L,R=0.999.Based on DMF/carboxyl/MWCNTs/ME,the linear equations were Ipa(A)=4.197×10-8+1.273×10-5c with linear range: 1.0×10-4~2.0×10-1 mol/L,R=0.998.Based on carboxyl/MWCNTs/PME,the linear equations were Ipa(?A)=3.259×10-2+1.801×102c with linear range: 5.00×10-6~9.50×10-4 mol/L,R=0.997.The recoveries were 99%~105%,97%~113%,96%~105% respectivly.