Transcript 下載/瀏覽Download

Preparation of the Carbon Paste Electrode Modified with Ferrocene and Its Applications to Detection of
Hydrogen Peroxide and Glucose
Yi-Sheng Wang (汪乙生) , 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
RESULTS AND DISCUSSION
A study was conducted to use the ferrocene to modify the carbon paste electrode which
was used as the working electrode to detect the responding current of reduction of hydrogen
peroxide and then the concentration of hydrogen peroxide could be obtained from the
responding current and consequently, the concentration of the glucose could be determined.
The TB (Time Base) graphs for different operating potentials, and pH values were plotted to
determine the optimum operating conditions. The results showed that the responding current
for the carbon paste electrode modified with ferrocene was elevated significantly. The
optimum weight ratio for ferrocene : graphite carbon powders was 3 : 7 . The optimum
operating conditions are -200mV operating potential, 500rpm stirring rate and in 0.05 M PBS
buffer solution( pH = 7.4 ) .
INTRODUCTION
Nowadays, diabetes is one of the top ten causes of death for the people in Taiwan .
Therefore, developing a rapid, convenient, and economical glucose biosensor for
detecting the glucose is a very 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. Because the ferrocene (Fe(C5H5)2) possesses
the excellent conductivity and catalytic characteristic, it can be used to elevate the
responding current for detection of reduction of hydrogen peroxide. A study was
conducted to use the ferrocene to modify the carbon paste electrode which was used as
the working electrode to detect the responding current of reduction of hydrogen peroxide
in the phosphate buffer solution(PBS) and then the concentration of hydrogen peroxide
could be obtained from the responding current and consequently, the concentration of the
glucose could be determined.
(A)
(B)
Fig 1. CV graphs for (A) carbon paste
electrode modified with ferrocene (B)
unmodified carbon paste electrode; the
range of scanning potential: -0.8～+0.8
V, scanning rate = 50 mV/s
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) –300mV (B) –200mV
(C) –100mV ]
EXPERIMENTAL SECTION
Equipment
Electrochemical Analyzer (BAS 100W) was used to measure the activity of electrode by
Cyclic Voltammetry ( CV ) and Time Base ( TB ) mode ; pH meter (Metrohm 731); Constant
Temperature Thermal Bath (Wisdom BC-2DT 10L); Oven (DENG YNG) ; Electric Stirrer
(Fargo); Carbon Paste Electrode was used as the working electrode, Coiled Platinum Wire was
used as the counter electrode and Ag / AgCl was used as the reference electrode.
Chemicals and Reagents
Fig. 3 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 = 6.0 (B) pH = 7.0 (C) pH =
7.4 (D) pH = 8.0 ]
Fig. 4 The TB graphs of carbon paste
electrodes for detection of H2O2 ;; (A)
carbon paste electrode modified with
ferrocene (ferrocene : graphite carbon
powders = 3 : 7); (B) unmodified
carbon paste electrode
Ferrocene(Fe(C5H5)2); Hydrogen Peroxide (H2O2); D(+)-Glucose Monohydrate(C6H12O6);
Glucose Oxidase(EC 1.1.3.4, Type X-S: From Aspergillus Niger, 50000 units/mg); Graphite
Carbon Powder; Carbon Paste; Cyclohexanone(C6H10O); Nafion ; Potassium
Dihydrogenphosphate (KH2PO4); Potassium Chloride (KCl).
Procedure
(1) 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.
0.5 cm
0.05cm
7 cm
(2) 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 nakeended electric wire and dried in the oven and then we obtained the carbon paste
electrode. The surface area of the carbon paste electrode was 0.0805 cm2 .
Ferrocene
Graphite carbon powders
Mixing with carbon
paste
Coated on
the nakeended
electric wire
Fig.5 The graphs for determining the
linear range of detection of H2O2 for
carbon paste electrode [ (A) carbon
paste electrode modified with ferrocene
(B) unmodified carbon paste electrode ]
Fig. 6 The TB graph of glucose biosensor
for detection of glucose (ferrocene : graphite
carbon powders = 3 : 7); At 30 ℃; the
operating potential = –200 mV; in 0.1 M KCl
of 5 mL 0.05 M PBS buffer solution
( pH=7.4 ); stirring rate=500 rpm; 20μL of
100mM glucose 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 optimum weight ratio for
ferrocene : graphite carbon powders was 3 : 7 . At 30℃ , -200mV operating potential,
and in 0.05 M 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 0.01 mM H2O2 , the linear range was 0.01～0.5 mM
H2O2 , R2=0.993, and the sensitivity was 260.6 μA/cm2．mM H2O2 . For the glucose
biosensor, the detection limit was 0.06 mM C6H12O6 ; the linear range was 0.06 ~ 2.0
mM C6H12O6 ; R2 = 0.992 and the sensitivity was 83.1 μA/cm2．mM C6H12O6 . The
optimum operating conditions are -200mV operating potential, 500rpm stirring rate
and in 0.05 M PBS buffer solution ( pH = 7.4 ) .
(3) After the above mentioned carbon paste electrode was dried, the 2μL glucose oxidase
solution( 3mg of glucose oxidase was dissolved in 500μL PBS buffer solution ) was put
onto the surface of electrode and the electrode was dried at room temperature. Then 5μL
of 1% Nafion solution(in 95% alcohol) was dropped onto the electrode evenly and after
the electrode was dried at room temperature, we obtained the glucose biosensor.
1 % Nafion
glucose oxidase
PVC cover
REFERENCES
1. P. C. Pandey and S. Upadhyay, “Bioelectrochemistry of Glucose Oxidase
Immobilized on Ferrocene Encapsulated Ormosil Modified Electrode,” Sensors
and Actuators B, Vol.76,193 (2001).
2. M. A. Kim and W.-Y. Lee, “Amperometric Phenol Biosensor Based on Sol-Gel
Silicate/Nafion Composite Film,” Analytica Chimica Acta, Vol.479, 143 (2003).
3. Y.-M. Uang and T.-C. Chou , “Fabrication of Glucose Oxidase/Polypyrrole
Biosensor by Galvanostatic Method in Various pH Aqueous Solutions,”
Biosensors and Bioelectronics, Vol.19, 141(2003).