H 2 O mol /L ~ mol /L

19 5 Vol. 19 No. 5 2010 10 Journal of Huaiyin Institute of Technology Oct. 2010 B 12 223003 B 12 VB 12 CNT /GC E O' 10 ~ 100 mv /s 0. 173 ± 0. 004 V - 0. 773 ± 0. 004 V vs. SCE ph 7. 0 ph VB 12 CNT /GC VB 12 H 2 O 2 H 2 O 2 H 2 O 2 4 10-5 mol /L ~ 4. 5 10-2 mol /L VB 12 H 2 O 2 B 12 O657 A 1009-7961 2010 05-0073 - 06 The Electrochemical Behavior of Vitamin B 12 at a Glassy Carbon Electrode Modified with Carbon Nanotubes CHEN Jing JIN Ye - Ling Faculty of Life Science & Chemical Engineering Huaiyin Institute of Technology Huai'an Jiangsu 223003 China Abstract Vitamin B 12 was immobilized on a CNT /GC electrode. The experimental results showed that CNTs could have promotion effect on the direct electron transfer of Vitamin B 12. Cyclic voltammetric results showed two pairs of redox peaks which corresponded to the direct electron transfer of Vitamin B 12 the average values of E O' are 0. 173 ± 0. 004 V and - 0. 773 ± 0. 004 V vs. SCE ph 7. 0 in the phosphate buffer solution in the scan rate range of 10 ~ 100 mv /s. The dependence of E O' on ph indicated that the direct electron transfer reaction of Vitamin B 12 was a one - electron transfer without proton transfer reaction process. The experimental results also demonstrated that the immobilized Vitamin B 12 retained their bioelectrocatalytic activity to the reduction of H 2 O 2 the linearity of calibration was between 4 10-5 and 4. 5 10-2 mol /L. Key words Vitamin B 12 Carbon nanotube direct electrochemistry chemically modified electrode 0 B 12 VB 12 B 12 B 12 B 12 Co Co III Co II Co I B 12 Rusling Zagal B 12 B 12 B 12 2010-07 - 20 1969 -

74 2010 1. 3 B 12 - VB 12 - CNT /GC SCE 25 ± 2 2 2. 1 B 12 CNT /GC 1a 1b GC VB 12 /GC - OH - COOH C = O 0. 1 mol /L PBS ph 5 0. 1 V /s GC VB 12 /GC VB 12 CNT /GC 1c - 50 mv CNT /GC CNT /GC VB 12 CNT /GC GC 1 1. 1 VB 12 - CNT /GC 0. 1 mol /L PBS ph 5 B 12 Sigma 30-50nm < 600nm > 95% 1d 1c 1d VB 12 0. 1 mol /L KH 2 PO 4 H 3 PO 4 H 2 O 2 30 % H 2 O 2 0. 1 mol /L PBS 2 mg /ml 30 min 1. 2 B 12 CNT /GC GC 3 mm 6 0. 3 0. 05 μm Al 2 O 3 2 min 1 GC a VB 12 /GC b CNT /GC c 25 μl 5 VB 12 - CNT /GC d 0. 1 mol /L PBS ph 5 μl VB 12 5 mg /ml 100 mv /s 0. 1 mol /L PBS B 12 Co 5 VB 12 VB 12 - CNT / Co III Co II Co I GC 4 Co III Co II CNT /GC Co II Co I VB 12 /GC CNT /GC CNT /GC CNT GC 1d 0. 174 V Vitamin B 12 Co III + e - Vi-

5 B 12 75 tamin B 12 Co II 0. 775 V Vitamin B 12 Co II + e - Vitamin B 12 Co I CNT CNT 1 100 mv /s VB12 c NADH CNT Epa 1 = 0. 716 V Epc 1 = 0. 834 V E O' 1 = 0. 775 2. 2 V Epa 2 = 0. 253 V Epc 2 = 0. 094 V E O' CNT 2 VB 12 - CNT /GC 0. 1 mol /L PBS 2 = 0. 174 V VB 12 CNT VB 12 2 VB 12 - CNT /GC 0. 1 mol /L PBS A ph 4. 5 B ph 9 a e 40 80 120 160 and 200 mv /s 2 v < 100 mv /s VB 12 0. 17V 0. 094 V ph 4. 5 0. 775 V - 0. 834 V ph 9 136 ipa /ipc = 1 ip v Epa Epc 0. 4 V O 2 + 2H + + 2e H 2 O 2 10-100 mv /s E O' 1 = 0. 173 0. 6 V H 2 O 2 + 2H + + 2e 2H 2 O ± 0. 003 V E O' 2 = - 0. 773 ± 0. 004 V CNT /GC 2 ph = 9 VB 12 > 100mV - 0. 4 V - 0. 6 V II Co I Co III Co II 0. 834 V - 0. 6 V VB 12 Lin ph 3 ph = 4. 5 ph 4. 5 Co II Co III 0. 253 Co 2. 3 ph

76 2010 3 VB 12 - CNT /GC ph ph 7 0. 1mol /L PBS mv / ph VB 12 CNT /GC ph 0. 17V 0. 775 V ph VB 12 ph ph VB 12 3 VB 12 - CNT /GC 0. 1 mol /L PBS ph 5. 0 7. 0 9. 0 200 mv /s ph 2. 4 B 12 - CNT /GC 3. 2 VB 12 4 VB 12 - CNT /GC H 2 O 2 0. 1 mol /L PBS ph 5 H 2 O 2 a 0 b 20 c 50 mmol /L 100 mv /s VB 12 - CNT /GC H 2 O 2 0. 1

5 B 12 77 mol /L PBS 4 a VB 12 - CNT /GC Vb 12 H 2 O 2 0. 1 mol /L PBS ph = 5 H 2 O 2 b 0. 1 mol /L PBS ph = 5 20 mmol /L H 2 O 2 VB 12 - CNT /GC VB 12 - CNT /GC VB 12 H 2 O 2 5 H 2 O 2 4 10-5 mol /L ~ 4. 5 10-2 mol /L VB 12 - CNT /GC H 2 O 2 c VB 12 H 2 O 2 0. 1 mol /L PBS ph = 5 50 5 mmol /L H 2 O 2 VB 12 - CNT /GC 5 H 2 O 2 H 2 O 2 2. 5 B 12 - CNT /GC 0. 173 ± 0. 004 V - 0. 773 ± 0. VB 12 - CNT /GC 20 mmol /L H 2 O 2 004 V VS. SCE ph 1. 23 ± 0. 06 ma VB 12 CNT /GC VB 12 - CNT /GC VB 12 - CNT /GC CNT /GC B 12 H 2 O 2 H 2 O 2 VB 12 - CNT /GC 93 % 22 74 % VB 12 1 Hisaeda Y Nishioka T Inoue Y et al. Electrochemical - CNT /GC reactions mediated by vitamin B12 derivatives in organic solvents J. Chem. Rev. 2000 198 21-37. 3 2 Banerjee R. Chemistry and Biochemistry of B12 M. New York Wiley 1999 1948-1998. B 12 CNT /GC 3 Darbre T Siljegovic V Amolins A et al. Novel Trends in Electroorganic Synthesis J. Springer - Verlag Tokyo 1998 395-397. E O' 10 ~ 100 mv /s 4 Darbre T Zheng D Fraga R et al. Immobilization of

78 2010 Vitamin B12 onto solid electrodes by electropolymerization of a catalyst - modified monomer Electrochem J. Soc. Proc. 2000 15 53-55. 5 Zheng D Darbre T Keese R J. Methanol and dimethylaniline as methylating agents of Co I corrinoids under a- cidic conditions J. Inorg. Biochem 1999 73 273-275. 6 Wedemeyer C E Darbre T Keese R. A Model for the Cobalamin - Dependent Methionine Synthase J. Chim. Acta. 1999 82 1173-1184. 7 Njue C K Nuthakki B Vaze A et al. Vitamin B12 - mediated electrochemical cyclopropanation of styrene J. Electrochem. Commun 2001 3 733-741. 8 Shao Y Mirkin M V Rusling J F Liquid /Liquid Interface as a Model System for Studying Electrochemical Catalysis in Microemulsions. Reduction of trans - 1 2 - Dibromocyclohexane with Vitamin B12 J. J. Phys. Chem. B 1997 101 3202-3208. 9 Zagal J H Aguirre M J Parodi C G et al. Electrocatalytic activity of vitamin B12 adsorbed on graphite electrode for the oxidation of cysteine and glutathione and the reduction of cystine. 374 215-221. Electroanal J. Chem. 1994 10 Zagal J H Páez M A. Electro - oxidation of hydrazine on electrode modified with vitamin B12 Electrochim J. Acta 1997 42 3477-3485. 11 Holliger C Wohlfahrt G Diekert G. Reductive dechlorination in the energy metabolism of anaerohic bacteria J. FEMS Rev. 1999 22 383-398. 12 McCauly K M Wilson S R. Synthesis and Characterization of Chlorinated Alkenylcobaloximes To Probe the Mechanism of Vitamin B12 - Catalyzed Dechlorination of Priority Pollutants J. Inorg. Chem. 2002 41 393-404. 13 Lin M S Leu H J Lai C H. Development of Vitamin B12 based disposable sensor for dissolved oxygen J. Analytica Chimica Acta 2006 561 164-166. 14 Ngandu L Robin D Kasmi A E et al. Vitamin B12 - transport protein interaction Electrochemistry of aque and glutathionnl - cobalamins adsorbed on carbon electrodes role of the nucleotide chain J. Chim. Acta 1999 292 204-209. 15 Borek V Morra M J. Cyclic voltammetry of aquocobalamin on clay - modified electrodes J. Environ. Sci. Technol 1998 32 2149-2153. 16 Vilakazi S L Nyokong T. Electrocatalytic properties of vitamin B12 towards oxidation and reduction of nitric oxide J. Electrochimica Acta 2000 46 453-457. 17 Porter M D Bright T B Allara D L. Chidsey C. E. D. J. Spontaneously organized molecular assemblies. 4. Structural characterization of n - alkyl thiol monolayers on gold by optical ellipsometry infrared spectroscopy and electrochemistr J. Am. Chem. Soc. 1987 109 3559-3566. 18 Wittkampf M Chemnitius G C Cammann K et al. Silicon thin film sensor for measurement of dissolved oxygen. Sens J. Actuators B 1997 43 40-42. 19 Hu S J Electroanal. Electrocatalytic reduction of molecular oxygen on a sodium montmorillonite - methyl viologen carbon pastechemically modified electrode J. Chem. 1999 463 253-255. 20 Tavar G Kalcher K Ogoreve B. Applicability of a Sol - Gel Derived CeO2 - TiO2 Thin Film Electrode as an Amperometric Sensor in Flow Injection J. Analyst 1997 122 371-376. 21 Glasspool W Atkinson J. A screen - printed amperometric dissolved oxygen sensor utilising an immobilised electrolyte gel and membrane J. Sens. Actuators B 1998 48 308-312. 22 Choi S H Ha J Shin J H et al. Planar amperometric oxygen sensor with improved preconditioning property J. Anal. Chim. Acta 2001 431 261-262. 23 Otten T Darbre T Cosnier S et al. ChemInform Abstract Synthesis of Vitamin - B12 Derivatives with an Electropolymerizable Side Chain J. Chim. Acta 1998 81 1117-1126. 24. J. 2004 32 3 381-387. 25 Wang J X Li M X Shi Z J et al. Direct Electrochemistry of Cytochrome c at a Glassy Carbon Electrode Modified with Single - Wall Carbon Nanotubes J. Anal. Chem. 2002 74 9 1993-1997. 26. J. 2006 64 24 2396-2402.