This work describes a glassy carbon electrode (GCE) modified by 4-((E)-(2-methyl-4-nitrophenylimino)
methyl) benzene-1,2-diol (abbreviated as MBD) and multiwall carbon nanotubes (MWNT) as an electrochemical
sensor for monitoring of levodopa (LD) concentration. Different electrochemical parameters of
MBD were obtained at MWCNT-GCE by cyclic voltammetry. Also the electrocatalytic behavior of LD was
investigated at the MBD-MWNT-GCE by cyclic voltammetry, chronoamperometry and differential pulse
voltammetry. Using the electrocatalysis of LD V in phosphate buffer solution pH 7.0 on this modified electrode
it is possible to obtain a linear calibration curve from 5.0 10 – 7 to 9.0 10 – 4 M and a detection limit
of 0.37 μM for LD by differential pulse voltammetry. The electrode was successfully applied for determination
of LD in real sample.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3493

Mazloum-Ardakani, M.

Mirjalili, B.B.F

Sheikh-Mohseni, M.A.

Yavari, M.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 1 No 2, 02NNBM04 (2pp) (2012) 
 
 
2304-1862/2012/1(2)02NNBM04(2) 02NNBM04-1  2012 Sumy State University 
Electrocatalytic Behavior of Levodopa at MultiWall Carbon Nanotubes and 4-((E)-(2-Methyl-4-
Nitrophenylimino) Methyl) Benzene-1,2-Diol Modified Glassy Carbon Electrode 
  
M. Mazloum-Ardakani*, M. Yavari, M.A. Sheikh-Mohseni, B.B.F. Mirjalili 
 
Department of Chemistry, Faculty of Science, Yazd University, I.R. Iran 
 
(Received 28 April 2012; published online12 July 2012) 
 
This work describes a glassy carbon electrode (GCE) modified by 4-((E)-(2-methyl-4-nitrophenylimino) 
methyl) benzene-1,2-diol (abbreviated as MBD) and multiwall carbon nanotubes (MWNT) as an electro-
chemical sensor for monitoring of levodopa (LD) concentration. Different electrochemical parameters of 
MBD were obtained at MWCNT-GCE by cyclic voltammetry. Also the electrocatalytic behavior of LD was 
investigated at the MBD-MWNT-GCE by cyclic voltammetry, chronoamperometry and differential pulse 
voltammetry. Using the electrocatalysis of LD V in phosphate buffer solution pH 7.0 on this modified elec-
trode it is possible to obtain a linear calibration curve from 5.0  10 – 7 to 9.0  10 – 4 M and a detection limit 
of 0.37 μM for LD by differential pulse voltammetry. The electrode was successfully applied for determina-
tion of LD in real sample. 
 
Keywords: Carbon nanotubes, Levodopa, Glassy carbon electrode, Electrocatalysis. 
 
  PACS numbers: 61.46.Fg, 07.07.Df 
 
 
______________ 
* mazloum@yazduni.ac.ir 
1. INTRODUCTION 
 
Levodopa (3,4-dihydroxyphenyl - l -alanine) is an 
important chemical substance and used in the treat-
ment of Parkinson’s disease. This substance is known 
to be converted into dopamine by an enzymatic reaction 
for the deficiency of dopamine in brain [1]. 
Several methods have been reported for the deter-
mination of levodopa including high performance liquid 
chromatography, gas chromatography, NMR spectros-
copy and electrochemical methods. The electrochemical 
methods caused a lot of attention because of their celer-
ity and sensitivity [1]. 
Carbon nanotubes (CNT), a novel carbon material 
discovered by Iijima in 1991, can be divided into multi-
wall carbon nanotubes (MWNT) and single-wall carbon 
nanotubes (SWNT). They have been the subject of nu-
merous investigations in many areas due to their novel 
structural, mechanical, electronic, and chemical prop-
erties. Because of their excellent electrocatalytic per-
formance, more and more electrochemistry researchers 
have begun to pay close attention to them [2]. We have 
studied the electrochemical behavior of MBD at 
MWNT-GCE. Also some electrocatalytic parameters of 
levodopa were measured at MBD-MWNT-GCE. 
 
2. EXPERIMENTAL 
 
2.1 Chemicals 
 
All solutions were freshly prepared with doubly dis-
tilled water. All the reagents were of analytical grade. 
Buffer solutions were prepared from orthophosphoric 
acid and its salts in the pH range of 2.0 – 12.0. MBD 
was synthesized in our laboratory. 
 
2.2 Apparatuses 
 
The electrochemical experiments were performed us-
ing a potentiostat/galvanostat (SAMA 500, electroana-
lyzer system, I.R. Iran). The cell configuration contained 
a glassy carbon as a working electrode, a Pt wire as an 
auxiliary electrode and a saturated calomel electrode as 
the reference electrode. All the potentials were recorded 
with respect to the reference electrode. A Metrohm 691 
pH/ion meter was also used for pH measurements. 
 
2.3 Preparation of MBD-MWNT-GCE 
 
For preparation of MBD-MWNT-GCE the flowing 
procedure was applied. The GCE surface was polished 
mechanically with alumina powders, using a polishing 
cloth until the electrode surfaces had a mirror-finish 
and then rinsed thoroughly with double distilled water. 
Electrochemical activation of the electrode was per-
formed by continuous potential cycling in sodium bi-
carbonate solution until a stable voltammogram was 
obtained. The activated GCE was coated by casting 
mixture of 3 μL MWNT. After being dried in the air 
overnight to remove the solvent, the MWNT-GCE was 
prepared. For modification by MBD, it was placed in a 
0.1 M phosphate buffer solution containing MBD and 
was modified by cycling the potential between 0.0 and 
0.5 V for 10 cycles. Finally, the electrode was rinsed 
thoroughly with water and dipped into the buffer solu-
tion (pH 7.0) to test its electrochemical behavior. 
 
3. RESULTS AND DISCUSSION  
 
3.1 Electrochemical behavior of MBD-MWNT-
GCE 
 
Experimental results show reproducible anodic and 
cathodic peaks (with Epa  0.148 V, Epc  0.135 V ver-
sus SCE and ΔEp  0.013 V) for MBD-MWNT-GCE at 
scan rate 100 mV/s in pH 7.0. The effects of the poten-
tial scan rate on the electrochemical properties of the 
MBD-MWNT-GCE were studied with cyclic voltamme-
try. Plots of the anodic and cathodic peak currents were 
linearly dependent on scan rates (Fig. 1 A). Fig. 1B 
shows the variations of peak potentials as a function of 
the logarithm of the potential scan rate. Based on this 
 
M. MAZLOUM-ARDAKANI, M. YAVARI, ET AL. PROC. NAP 1, 02NNBM04 (2012) 
 
 
02NNBM04-2 
equation the cathodic transfer coefficient (α) and elec-
tron transfer rate constant for MBD-MWNT-GCE calcu-
lated as 0.43 and 18.54 s – 1, respectively. 
 
 
 
Fig. 1 – (A) Variation of Ip versus scan rates (B) Variation of 
Ep versus the logarithm of the high scan rate 
 
3.2 Electrocatalysis of levodopa at MBD-MWNT-
GCE 
 
The effect of scan rate on the electrocatalytic oxidation 
of LD at the MBD-MWNT-GCE was investigated by cyclic 
voltammetry (Fig. 2). The plot of peak height versus the 
square root of the scan rate was constructed (Fig. 2 inset). 
This plot was found to be linear, suggesting that the pro-
cess of oxidation of LD was diffusion-controlled [3]. 
 
 
 
Fig. 2 – Cyclic voltammograms of MBD-MWNT-GCE in 
phosphate buffer (pH 7.0) containing 1.0 mM levodopa at 
different scan rates (from inner to outer 10, 20, 30, 40, 60, 80 
and 100 mV/s), Insets: Variation of the electrocatalytic 
currents versus the square root of the scan rate 
 
3.3 Determination of levodopa by differential 
pulse voltammetry 
 
Differential pulse voltammetry (DPV) was used for 
determination of levodopa at MBD-MWNT-GCE. Fig. 3 
shows the DPVs of different concentrations of levodopa at 
MBD-MWNT-GCE. Linear calibration curve was ob-
tained in the rang of 5.0  10 – 7 to 9.0  10 – 4 M. Also the 
detection limit was calculated as 0.37 μM for levodopa. 
 
 
 
Fig. 3 – DPVs of MBD-MWNT-GCE in 0.1 M phosphate buffer 
solution (pH 7.0) containing different concentrations of 
levodopa (from inner to outer): 0.5, 1.0, 5.0 10.0, 15.0, 20.0, 
50.0, 100.0, 300.0, 500.0, 700.0 and 900.0. Insets show the 
plots of the electrocatalytic peak current as a function of 
levodopa concentration in the range of: (A) 0.5 to 20.0 µM and 
(B) 20.0 to 900.0 µM 
 
CONCLUSIONS 
 
A glassy carbon electrode has been modified with 
MBD and MWNT. The electrochemical behaviors of MBD 
were investigated. Also this modified electrode was used 
for electrocatalytic determination of LD. The results 
demonstrated that the electrooxidation of LD at the sur-
face of MBD-MWNT-GCE occurs at a potential about 
328 mV less positive than bare glassy carbon electrode. 
The modified electrode has been shown to be promising 
for LD detection with many desirable properties includ-
ing good reproducibility, high sensitivity, excellent cata-
lytic activity, low detection limit and especially its anti-
fouling properties towards LD and its oxidation products. 
 
AKNOWLEDGEMENTS 
 
The authors wish to thank the Yazd University 
Research Council, IUT Research Council and Excellence 
in Sensors for financial support of this research. 
 
REFERENCES 
 
1. M. Mazloum-Ardakani, B. Ganjipour, H. Beitollahi, M.K. 
Amini, F. Mirkhalaf, H. Naeimi, M. Nejati-Barzoki, Elec-
trochim. Acta 56 No 25, 9113 (2011). 
2. M. Mazloum-Ardakani, H. Beitollahi, B. Ganjipour, 
H. Naeimi, M. Nejati, Bioelectrochemistry 75 No 1, 1 
(2009). 
3 A.J. Bard, L.R. Faulkner, Electrochemical Methods: Fun-
damentals and Applications (New York, Wiley, 2001). 


Electrocatalytic Behavior of Levodopa at MultiWall Carbon Nanotubes and 4-((E)-(2-Methyl-4-Nitrophenylimino) Methyl) Benzene-1,2-Diol Modified Glassy Carbon Electrode

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 1 No 2, 02NNBM04 (2pp) (2012)   2304-1862/2012/1(2)02NNBM04(2) 02NNBM04-1  2012 Sumy State University Electrocatalytic Behavior of Levodopa at MultiWall Carbon Nanotubes and 4-((E)-(2-Methyl-4-Nitrophenylimino) Methyl) Benzene-1,2-Diol Modified Glassy Carbon Electrode   M. Mazloum-Ardakani*, M. Yavari, M.A. Sheikh-Mohseni, B.B.F. Mirjalili  Department of Chemistry, Faculty of Science, Yazd University, I.R. Iran  (Received 28 April 2012; published online12 July 2012)  This work describes a glassy carbon electrode (GCE) modified by 4-((E)-(2-methyl-4-nitrophenylimino) methyl) benzene-1,2-diol (abbreviated as MBD) and multiwall carbon nanotubes (MWNT) as an electro-chemical sensor for monitoring of levodopa (LD) concentration. Different electrochemical parameters of MBD were obtained at MWCNT-GCE by cyclic voltammetry. Also the electrocatalytic behavior of LD was investigated at the MBD-MWNT-GCE by cyclic voltammetry, chronoamperometry and differential pulse voltammetry. Using the electrocatalysis of LD V in phosphate buffer solution pH 7.0 on this modified elec-trode it is possible to obtain a linear calibration curve from 5.0  10 – 7 to 9.0  10 – 4 M and a detection limit of 0.37 μM for LD by differential pulse voltammetry. The electrode was successfully applied for determina-tion of LD in real sample.  Keywords: Carbon nanotubes, Levodopa, Glassy carbon electrode, Electrocatalysis.    PACS numbers: 61.46.Fg, 07.07.Df   ______________ * mazloum@yazduni.ac.ir 1. INTRODUCTION  Levodopa (3,4-dihydroxyphenyl - l -alanine) is an important chemical substance and used in the treat-ment of Parkinson’s disease. This substance is known to be converted into dopamine by an enzymatic reaction for the deficiency of dopamine in brain [1]. Several methods have been reported for the deter-mination of levodopa including high performance liquid chromatography, gas chromatography, NMR spectros-copy and electrochemical methods. The electrochemical methods caused a lot of attention because of their celer-ity and sensitivity [1]. Carbon nanotubes (CNT), a novel carbon material discovered by Iijima in 1991, can be divided into multi-wall carbon nanotubes (MWNT) and single-wall carbon nanotubes (SWNT). They have been the subject of nu-merous investigations in many areas due to their novel structural, mechanical, electronic, and chemical prop-erties. Because of their excellent electrocatalytic per-formance, more and more electrochemistry researchers have begun to pay close attention to them [2]. We have studied the electrochemical behavior of MBD at MWNT-GCE. Also some electrocatalytic parameters of levodopa were measured at MBD-MWNT-GCE.  2. EXPERIMENTAL  2.1 Chemicals  All solutions were freshly prepared with doubly dis-tilled water. All the reagents were of analytical grade. Buffer solutions were prepared from orthophosphoric acid and its salts in the pH range of 2.0 – 12.0. MBD was synthesized in our laboratory.  2.2 Apparatuses  The electrochemical experiments were performed us-ing a potentiostat/galvanostat (SAMA 500, electroana-lyzer system, I.R. Iran). The cell configuration contained a glassy carbon as a working electrode, a Pt wire as an auxiliary electrode and a saturated calomel electrode as the reference electrode. All the potentials were recorded with respect to the reference electrode. A Metrohm 691 pH/ion meter was also used for pH measurements.  2.3 Preparation of MBD-MWNT-GCE  For preparation of MBD-MWNT-GCE the flowing procedure was applied. The GCE surface was polished mechanically with alumina powders, using a polishing cloth until the electrode surfaces had a mirror-finish and then rinsed thoroughly with double distilled water. Electrochemical activation of the electrode was per-formed by continuous potential cycling in sodium bi-carbonate solution until a stable voltammogram was obtained. The activated GCE was coated by casting mixture of 3 μL MWNT. After being dried in the air overnight to remove the solvent, the MWNT-GCE was prepared. For modification by MBD, it was placed in a 0.1 M phosphate buffer solution containing MBD and was modified by cycling the potential between 0.0 and 0.5 V for 10 cycles. Finally, the electrode was rinsed thoroughly with water and dipped into the buffer solu-tion (pH 7.0) to test its electrochemical behavior.  3. RESULTS AND DISCUSSION   3.1 Electrochemical behavior of MBD-MWNT-GCE  Experimental results show reproducible anodic and cathodic peaks (with Epa  0.148 V, Epc  0.135 V ver-sus SCE and ΔEp  0.013 V) for MBD-MWNT-GCE at scan rate 100 mV/s in pH 7.0. The effects of the poten-tial scan rate on the electrochemical properties of the MBD-MWNT-GCE were studied with cyclic voltamme-try. Plots of the anodic and cathodic peak currents were linearly dependent on scan rates (Fig. 1 A). Fig. 1B shows the variations of peak potentials as a function of the logarithm of the potential scan rate. Based on this  M. MAZLOUM-ARDAKANI, M. YAVARI, ET AL. PROC. NAP 1, 02NNBM04 (2012)   02NNBM04-2 equation the cathodic transfer coefficient (α) and elec-tron transfer rate constant for MBD-MWNT-GCE calcu-lated as 0.43 and 18.54 s – 1, respectively.    Fig. 1 – (A) Variation of Ip versus scan rates (B) Variation of Ep versus the logarithm of the high scan rate  3.2 Electrocatalysis of levodopa at MBD-MWNT-GCE  The effect of scan rate on the electrocatalytic oxidation of LD at the MBD-MWNT-GCE was investigated by cyclic voltammetry (Fig. 2). The plot of peak height versus the square root of the scan rate was constructed (Fig. 2 inset). This plot was found to be linear, suggesting that the pro-cess of oxidation of LD was diffusion-controlled [3].    Fig. 2 – Cyclic voltammograms of MBD-MWNT-GCE in phosphate buffer (pH 7.0) containing 1.0 mM levodopa at different scan rates (from inner to outer 10, 20, 30, 40, 60, 80 and 100 mV/s), Insets: Variation of the electrocatalytic currents versus the square root of the scan rate  3.3 Determination of levodopa by differential pulse voltammetry  Differential pulse voltammetry (DPV) was used for determination of levodopa at MBD-MWNT-GCE. Fig. 3 shows the DPVs of different concentrations of levodopa at MBD-MWNT-GCE. Linear calibration curve was ob-tained in the rang of 5.0  10 – 7 to 9.0  10 – 4 M. Also the detection limit was calculated as 0.37 μM for levodopa.    Fig. 3 – DPVs of MBD-MWNT-GCE in 0.1 M phosphate buffer solution (pH 7.0) containing different concentrations of levodopa (from inner to outer): 0.5, 1.0, 5.0 10.0, 15.0, 20.0, 50.0, 100.0, 300.0, 500.0, 700.0 and 900.0. Insets show the plots of the electrocatalytic peak current as a function of levodopa concentration in the range of: (A) 0.5 to 20.0 µM and (B) 20.0 to 900.0 µM  CONCLUSIONS  A glassy carbon electrode has been modified with MBD and MWNT. The electrochemical behaviors of MBD were investigated. Also this modified electrode was used for electrocatalytic determination of LD. The results demonstrated that the electrooxidation of LD at the sur-face of MBD-MWNT-GCE occurs at a potential about 328 mV less positive than bare glassy carbon electrode. The modified electrode has been shown to be promising for LD detection with many desirable properties includ-ing good reproducibility, high sensitivity, excellent cata-lytic activity, low detection limit and especially its anti-fouling properties towards LD and its oxidation products.  AKNOWLEDGEMENTS  The authors wish to thank the Yazd University Research Council, IUT Research Council and Excellence in Sensors for financial support of this research.  REFERENCES  1. M. Mazloum-Ardakani, B. Ganjipour, H. Beitollahi, M.K. Amini, F. Mirkhalaf, H. Naeimi, M. Nejati-Barzoki, Elec-trochim. Acta 56 No 25, 9113 (2011). 2. M. Mazloum-Ardakani, H. Beitollahi, B. Ganjipour, H. Naeimi, M. Nejati, Bioelectrochemistry 75 No 1, 1 (2009). 3 A.J. Bard, L.R. Faulkner, Electrochemical Methods: Fun-damentals and Applications (New York, Wiley, 2001). 

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Electrocatalytic Behavior of Levodopa at MultiWall Carbon Nanotubes and 4-((E)-(2-Methyl-4-Nitrophenylimino) Methyl) Benzene-1,2-Diol Modified Glassy Carbon Electrode

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