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The Optimum Operating Conditions for Detection of Hydrogen Peroxide for the Carbon Paste Electrode Modified with Ferrocene
Pao-Tsai Kuo (郭寶財), Chung-Min Lien (連崇閔), Hau Lin (林浩)
Department of Chemical and Materials Engineering, Southern Taiwan University
ABSTRACT
A study was conducted to use the ferrocene to modify the carbon paste electrode. Because the ferrocene(Fe(C5H5)2) possesses the excellent catalytic characteristic, it can be used with the graphite carbon powders
which possesses the excellent conductivity to make the carbon paste electrode and to elevate the responding current of hydrogen peroxide. The responding current of hydrogen peroxide is detected in the phosphate
buffer solution(PBS) and then the concentration of the hydrogen peroxide can be obtained and consequently, the concentration of the glucose can be determined. At optimum operating conditions - 0.2V operating
potential, 500 rpm stirring rate and in 0.05M PBS buffer solution ( pH = 7.4 ) , when the carbon paste electrode was modified with the ferrocene [ferrocene : graphite carbon powders = 3 : 7 ( weight ratio )] , the
detection limit was 0.02 mM H2O2 , the linear range was 0.02～1.2 mM H2O2 , R2 = 0.9998 and the sensitivity was 161.43µA/cm2．mM H2O2.
INTRODUCTION
RESULTS
Because hydrogen peroxide is widely used in the food industry for the purpose of preservation
nowadays, a rapid and convenient sensor for detecting hydrogen peroxide is an important research subject.
In recent years, diabetes has become one of the top ten causes of death for the people in Taiwan. Therefore
developing a rapid and convenient glucose biosensor also has become an important research subject. The
glucose and oxygen can be catalyzed by the glucose oxidase and the glucose is oxidized to gluconic acid
and the oxygen is reduced to hydrogen peroxide. The electrode releases the electrons and converts the
mediator to the reductive state. Then the mediator at the reductive state releases the electrons to reduce the
hydrogen peroxide to water and consequently the mediator at the reductive state is converted to the
oxidizing state. The responding current for detecting the hydrogen peroxide is used to measure the amount
of hydrogen peroxide and consequently determine the concentration of the glucose. Because the
ferrocene(Fe(C5H5)2) possesses the excellent catalytic characteristic, it can be used with the graphite carbon
powders which possesses the excellent conductivity to make the carbon paste electrode and to elevate the
responding current of hydrogen peroxide. The responding current of hydrogen peroxide is detected in the
phosphate buffer solution(PBS) and then the concentration of the hydrogen peroxide can be obtained and
consequently, the concentration of the glucose can be determined.
(A)
(B)
Fig 1. CV graphs for (A) carbon paste electrode
modified with ferrocene ( the range of scanning potential:
-0.8～+0.8 V) (B) unmodified carbon paste electrode( the
range of scanning potential: -0.8～+0.8 V)
Fig. 2 The TB graphs of carbon paste electrode for
detection of H2O2 at different operating potentials
(ferrocene : graphite carbon powders = 3 : 7); the
operating potentials are [ (A) 0V (B) –0.1V (C) –0.15V
(D) –0.2V (E) –0.25 V ]
EXPERIMENTAL
1. Equipment
Electrochemical Analyzer (CHI 401A, CH Instruments, Inc) was used to measure the activity of
electrode by Cyclic Voltammetry ( CV ) and Time Base ( TB ) mode ; Electric Stirrer(Fargo) ; pH
meter (Metrohm 731); Constant Temperature Thermal Bath (Wisdom BC-2DT 10L); Oven (DENG
YNG) ; Carbon Paste Electrode was used as the working electrodes, Coiled Platinum Wire was
used as the counter electrode and Ag / AgCl was used as the reference electrode.
2. Chemicals and Reagents
Ferrocene ; Hydrochloric Acid (HCl); Sodium Hydroxide (NaOH) ; Hydrogen Peroxide (H2O2);
Graphite Carbon Powder( C ); Carbon Paste; Cyclohexanone(C6H10O); Potassium
Dihydrogenphosphate (KH2PO4); Potassium Chloride (KCl).
3. Preparation of the Carbon Paste Electrode :
Take one section of 7 cm electric wire with 0.05 cm inside diameter. After depriving the coating
0.5 cm length from both ends, the nake-ended wire was washed, dried and ready for use. Then the
ferrocene powders, graphite carbon powders and carbon paste were mixed with the appropriate
ratio (ferrocene : graphite carbon powders : carbon paste = 0.3 : 0.7 : 1). After the mixing was
complete, the mixture was evenly coated on the nake-ended electric wire and dried in the oven and
then we obtained the carbon paste electrode.
Fig. 3 The TB graphs of carbon paste electrode for
detection of H2O2 at different stirring rates
(ferrocene : graphite carbon powders = 3 : 7); the
stirring rates are [ (A) 100 rpm (B) 200 rpm (C) 300
rpm (D) 400 rpm (E) 500 rpm ]
7 cm
Fig. 5 The TB graphs of carbon paste electrode for
determining the detection limit of H2O2 (ferrocene: graphite
carbon powders = 3 : 7); At 30 ℃; the operating potential = –
0.2 V; in 0.1 M KCl of 5 mL 0.05 M PBS buffer solution ( pH=
7.4 )
0.05 cm
0.5 cm
Fig. 4 The TB graphs of carbon paste electrode for
detection of H2O2 at different pH values of PBS
buffer solution (ferrocene : graphite carbon powders
= 3 : 7); the pH values are [ (A) pH = 4.0 (B) pH = 5.0
(C) pH = 6.0 (D) pH = 7.4 (E) pH = 8.0 ]
Fig. 6 The TB graphs of carbon paste electrode for
determining the linear range of H2O2 (ferrocene :
graphite carbon powders = 3 : 7); At 30 ℃; the
operating potential = –0.2 V; in 0.1 M KCl of 5 mL 0.05
M PBS buffer solution ( pH= 7.4 ); stirring rate =500
rpm; 10μL of 100mM H2O2 is injected per 100 seconds
CONCLUSIONS
The results showed that the responding current for the carbon paste electrode modified with
ferrocene was elevated significantly. The TB (Time Base ) graphs for different operating potentials,
stirring rates, and pH values were plotted to determine the optimum operating conditions. The
results showed that at the optimum operating conditions –0.2 V operating potential, 500 rpm
stirring rate and in 0.05M PBS buffer solution (pH=7.4), the detection limit was 0.02 mM H2O2, the
linear range was 0.02~1.2 mM H2O2, R2=0.9998 and the sensitivity was 161.43μA/cm2ּmM H2O2. This
research can be further applied to the glucose biosensor in the future.
Ferrocene
REFERENCES
Mixing with equal
amount of carbon
paste
Graphite carbon
powders
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DEPARTMENT OF CHEMICAL AND MATERIALS ENGINEERING, SOUTHERN TAIWAN UNIVERSITY