Investigation And Application Of Electrochemical Behavior Of Vitamins Using A Silver Doped Poly Amino Acid Modified Electrode

In this paper, slver doped poly L-argenine modified glassy carbon electrode(Ag-PLA/GCE) was fabricated by cyclic voltammetric method, and some electrochemicalbehavior including the adsorption and diffusion characteristics of ascorbic acid (vitamin C),rutin, vitamin B2, vitamin B12and vitamin B6were studied on the modified electrode. Newmethods for individually and simultaneously determining vitamins were developed. Withadding silver during the electrochemical polymerization of L-argenine, the catalytic abilityof modified electrode was enhanced, which further improved the determination sensitivityand declined the detection limit of vitamin. In comparation with bare glassy carbonelectrode, Ag-PLA/GCE could decrease electrochemical impedance and accelerate theelectron transfer. The Ag-PLA/GCE electrode was of high sensitivity and selectivity, andhad been successfully applied to determine vitamin C, rutin, vitamin B2, vitamin B12andvitamin B6in samples.The major problems to be solve in working process are as fellows:1) Fabrication ofAg-PLA/GCE and investigation of catalytic ability and electrochemical impedance;2)Study of electrochemical behavior of ascorbic acid;3) Study of electrochemical behaviorof rutin;4) Study of electrochemical behavior of vitamin B2;5) Study of electrochemicalbehavior of vitamin B12;6) Study of electrochemical behavior of vitamin B6;7) Individualdetermination of ascorbic acid;8) Simultaneous determination of ascorbic acid and rutin;9)Simultaneous determination of vitamin B2and vitamin B12;10) Simultaneousdetermination of vitamin B2, vitamin C and vitamin B6.The main works and the detail achievements were exhibited as follows:1. The silver doped poly L-arginine modified glassy carbon electrode (Ag-PLA/GCE) wasprepared by electropolymerization method (Cyclic voltammetry). The voltammetricbehavior for ascorbic acid (AA) was studied on that electrode and a determination methodwas set up．In pH2.5phosphate buffer solution and at a scan rate of0.12V·s-1,Ag-PLA/GCE gave a sensitive oxidation peak at0.287V (vs. Ag/AgCl). The linear response was obtained in the range of5.00×10-6~5.00×10-3mol·L-1. The detection limitwas1.0×10-6mol·L-1.2. Ag-PLA/GCE was applied to study electrochemical behavior of rutin and ascorbic acid(AA). A new method of simultaneous determination of rutin and ascorbic acid wasestablished in the basis of optimum conditions. In pH2.5phosphate buffer solution at ascan rate of0.14V·s-1, two sensitive oxidation peaks at0.552V for rutin and0.281V forAA (vs. Ag/AgCl) were presented respectively. Besides, a reduction peak at0.491V forrutin was gave at Ag-PLA/GCE. The two oxidation peaks of rutin and AA could beseparated by0.271V. The determination linear range for rutin and AA were5.00×10-7mol·L-1~2.00×10-5mol·L-1and2.50×10-5mol·L-1~5.00×10-3mol·L-1, respective. Thedetection limits for rutin and AA were1.0×10-7mol·L-1and1.0×10-5mol·L-1, respectively.3. Vitamin B2(VB2) and vitamin B12(VB12) were analyzed by differential pulsevoltammetry at Ag-PLA/GCE. In pH5.0phosphate buffer solution, two sensitive oxidationpeaks at-0.470V for and-0.880V (vs. Ag/AgCl) were exhibited for VB2and VB12,respectively, based on the optimum conditions. The two oxidation peaks of VB2and VB12could be separated by0.410V, and it was no need to make separation for VB2and VB12inadvance. The determination linear range for VB2and VB12were1.00×10-7~1.50×10-5mol·L-1and7.50×10-7~1.25×10-5mol·L-1, respectively. And the detection limits for VB2and VB12were3.0×10-8mol·L-1and5.0×10-7mol·L-1, respectively.4. Vitamin B2(VB2), vitamin C (VC) and vitamin B6(VB6) were studied by cyclicvoltammetry and linear sweep voltammetry at Ag-PLA/GCE. The results indicate thatunder optimal conditions, Ag-PLA/GCE gave three sensitive oxidation peaks using LSV at-0.298V for VB2,0.317V for VC and1.058V for VB6(vs. Ag/AgCl), respectively. Andthe oxidation peak separations between VB2and VC, VC and VB6at modified electrodemethod were0.615V and0.741V. The linear ranges for VB2, VC and VB6were1.00×10-7~2.25×10-5mol L1,5.00×10-6~4.00×10-3mol L1and1.00×10-5~3.00×10-3molL1, respectively. The detection limits were8.0×10-8,3.0×10-6and5.0×10-6mol L1,respectively. The modified electrode has been successfully applied to simultaneously determine VB2, VC and VB6in multivitamin tablets with satisfactory results.