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The Operating Potential on the Sensitivity of Detection of Hydrogen Peroxide for the Carbon Paste Electrode Modified with Ferrocene
Pao-Tsai Kuo (郭寶財) , Ting-Li Lin (林庭立) , Hau Lin (林浩)
Department of Chemical and Materials Engineering, Southern Taiwan University
南台科技大學化學工程與材料工程系
ABSTRACT
Due to wide use of hydrogen peroxide in the industry and food preservation, a rapid and convenient sensor for detecting the hydrogen peroxide is an important research subject. 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 possess 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 30℃, and in 0.05
M phosphate buffer solution (PBS), the TB (Time Base) graphs for the carbon paste electrode at different operating potentials were plotted to evaluate the effect of the operating potential on the responding current of detection of hydrogen peroxide. At
the optimum operating conditions -0.2 V operating potential, 500 rpm stirring rate and in 0.05M PBS buffer solution ( pH = 7.4 ) , when the carbon paste electrode was modified with 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. This study can be further applied to the glucose biosensor.
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 the 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 our country. 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 at the reductive
potential 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. Therefore, the detecting technique for the hydrogen peroxide is an important research
subject. Because the ferrocene(Fe(C5H5)2) possesses the excellent catalytic characteristic, it can be used with the graphite carbon
powders which possess 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
30℃, and in 0.05 M phosphate buffer solution (PBS), the TB (Time Base) graphs for the carbon paste electrode at different
operating potentials were plotted to evaluate the effect of the operating potential on the responding current of detection of
hydrogen peroxide. The optimum operating conditions were used to detect the detection limit , linear range and sensitivity of
detection of hydrogen peroxide for the carbon paste electrode modified with ferrocene.
(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 electrodes for
detection of H2O2 at different operating potentials
(ferrocene : graphite carbon powders = 3 : 7); the
operating potentials are [ (A) 0V (B) –0.05V (C) –0.1V
(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 :
Fig. 3 The calibration curves of different operating
potentials for the carbon paste electrode modified with
ferrocene [ (A) 0V (B) –0.1V (C) –0.15V (D) –0.2V (E)
–0.25 V ]
Table 1 The sensitivities, responding currents, and R2
values of different operating potentials for the carbon paste
electrode modified with ferrocene
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.
7 cm
Fig. 4 The TB graphs of carbon paste electrodes 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. 5 The TB graphs of carbon paste electrodes 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 the
ferrocene was elevated significantly. The TB (Time Base ) graphs at different operating potentials
were plotted to evaluate the effect of the operating potential on the responding current of detection
of hydrogen peroxide and determine the optimum operating conditions. Because when the
operating potential was -0.25V, it caused the detection to be unstable, -0.2V operating potential
was used in this research. Because the pH of human blood is about 7.4, phosphate buffer solution
pH=7.4 was used in this study. The results showed that at the optimum operating conditions –0.2V
operating potential, 500rpm stirring rate and in 0.05M phosphate 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 161.43 μA/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