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A Factorial Design for Detection of Hydrogen Peroxide for Carbon Paste Electrode Modified with Ferrocene
Pao-Tsai Kuo (郭寶財) , Chih-Ying Wu (巫致穎 ) , 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
Nowadays, sometimes the hydrogen peroxide is used in the industry and food preservation, and therefore developing a hydrogen peroxide sensor which can detect the hydrogen peroxide rapidly and conveniently is an important research subject. In
recent years, the diabetes has become one of the top ten causes of death for the people in Taiwan. Therefore, developing a glucose biosensor which can detect the glucose rapidly and conveniently is also an important research subject. The glucose and oxygen
can be catalyzed by the glucose oxidase to produce the gluconic acid and hydrogen peroxide. A study of experimental design involving three factors (operating potential, stirring rate, and pH value of PBS) and two levels was performed to analyze the effect of
reaction parameters on the sensitivity of detection of hydrogen peroxide for the carbon paste electrode modified with ferrocene . The results showed that the main effect of operating potential ( F = 151.494, p value ＜ 0.05 ), the main effect of stirring rate ( F
= 7.288, p value ＜ 0.05 ), and the main effect of pH value ( F = 94.461, p value ＜ 0.05 ) were significant on the sensitivity. At 30℃, -200 mV operating potential, 500 rpm stirring rate and in 0.05 M PBS buffer solution ( pH = 7.4 ) , when the carbon paste
electrode was modified with ferrocene [ferrocene : carbon powders : carbon paste = 0.3 ：0.7 ：1 ( 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 was161.43 µA/cm2．mM
H2 O 2 .
INTRODUCTION
RESULTS
Because sometimes the hydrogen peroxide is 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 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 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 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 study of experimental design involving three factors (operating potential, stirring rate, and pH value of
PBS) and two levels was performed to analyze the effect of reaction parameters on the 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)
Table 1 Three factors and two levels of the factorial
design
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).
Table 2 The results of the sixteen experiments of the
experimental design ( A: Operating Potential(mV), B:
Stirring Rate(rpm), C: pH valus )
Table 3 The results of analysis of variance for the
sensitivity of detection of hydrogen peroxide for the carbon
paste electrode modified with ferrocene
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.
7 cm
Table 4 The TB graphs of carbon paste electrode for
determining the detection limit of H2O2 (ferrocene:
graphite carbon powders = 3 : 7)
0.05 cm
0.5 cm
Table 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 =
–200mV; 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. For the experimental design, the results showed that the main
effect of operating potential ( F = 151.494, p value ＜ 0.05 ), the main effect of stirring rate ( F =
7.288, p value ＜ 0.05 ), and the main effect of pH value ( F = 94.461, p value ＜ 0.05 ) were
significant on the sensitivity. Because the pH of human blood is about 7.4, pH = 7.4 was used in this
research. The results showed that the optimum operating conditions for this research were operating
potential = –200mV, stirring rate = 500 rpm, and pH = 7.4. Also the results showed that at –200mV
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 was0.02~1.2 mM H2O2, R2=0.9998 and the sensitivity was
161.43 μA/cm2ּmM H2O2.
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