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The Effect of Operating Potential on the Sensitivity of Detection of Hydrogen Peroxide for the Carbon Paste Electrode Modified
with Cobalt Hexacyanoferrate
Ting-Li Lin (林庭立) , 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
ABSTRAC
T
Developing a reliable, rapid and economical method for detecting hydrogen peroxide and glucose is an important research subject. Because the Cobalt Hexacyanoferrate possesses the excellent catalytic characteristic, it can be used with the graphite carbon powders and
carbon paste to make the carbon paste electrode to elevate the sensitivity of responding current of hydrogen peroxide. The responding current of hydrogen peroxide can be detected in phosphate buffer solution (PBS) and then the concentration of hydrogen peroxide can be
determined. 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. Therefore, as the concentration of hydrogen peroxide can be determined the concentration of the glucose
can also be determined. A study was conducted to use the Cobalt Hexacyanoferrate to modify the carbon paste electrode [Cobalt Hexacyanoferrate : graphite carbon powders = 3 : 7(weight ratio)] to elevate the sensitivity of responding current of detection of hydrogen
peroxide. The CV ( Cyclic Voltammetry ) graphs were plotted for the carbon paste electrode modified with Cobalt Hexacyanoferrate (Cobalt Hexacyanoferrate : graphite carbon powders : carbon paste = 0.3 : 0.7 : 1) and the unmodified carbon paste electrode. The results
showed that the responding current for the carbon paste electrode modified with Cobalt Hexacyanoferrate was elevated significantly. At 30℃, 700rpm stirring rate and in 0.05 M phosphate buffer solution ( pH=7.4 ), 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 -200mV operating potential, 700 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 0.02～1.8 mM H2O2 , R2 = 0.9990 and the sensitivity was 181.52µA/cm2．mM H2O2.
INTRODUCTION
RESULTS
Hydrogen peroxide is widely 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, 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. Because the cobalt hexacyanoferrate possesses the excellent
catalytic characteristic it can be used with the carbon paste and graphite carbon powders which possess
the excellent conductivity to make the carbon paste electrode and to elevate the responding current of the
hydrogen peroxide. The carbon paste electrode is used to detect the responding current of hydrogen
peroxide in PBS buffer solution and the concentration of hydrogen peroxide can be determined from the
responding current of hydrogen peroxide. The glucose and oxygen can be catalyzed by the glucose
oxidase to produce gluconic acid and hydrogen peroxide, and the concentration of the glucose can then
be determined. A study was conducted to use the cobalt hexacyanoferrate [cobalt hexacyanoferrate :
graphite carbon powders = 3 : 7(weight ratio)] to modify the carbon paste electrode to elevate the
responding current of detection of the hydrogen peroxide at different operating potentials. The TB (Time
Base ) graphs and calibration curves for different operating potentials were plotted to determine the
optimum operating conditions in this research.
Fig. 1 CV graphs for (A) carbon paste electrode modified
with cobalt hexacyanoferrate ( the range of scanning potential:
-0.8～+0.8 V) and (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 (cobalt hexacyanoferrate :
graphite carbon powders = 3 : 7); the operating potentials are [ (A)
-50mV (B) –100mV (C) –150mV (D) –200mV (E) –250mV ]
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 ;
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 electrodes, Coiled Platinum Wire was used as the counter electrode and
Ag / AgCl was used as the reference electrode.
Fig. 3 The calibration curves of different operating potentials for
the carbon paste electrode modified with cobalt hexacyanoferrate
[ ( A) -50mV (B) –100mV (C) –150mV (D) –200mV (E) –250mV ]
Table 1 The sensitivities, responding currents, and R2 values of
different operating potentials for the carbon paste electrode modified
with cobalt hexacyanoferrate
2. Chemicals and Reagents:
Cobalt(II) Acetate, Tetrahydrate (CH3COO)2Co．4H2O) ; Potassium
Hexacyanoferrate(ⅡI)( K3[Fe(CN)6] ) ; Hydrochloric Acid (HCl); Sodium Hydroxide
(NaOH) ; Hydrogen Peroxide (H2O2); Graphite Carbon Powder ; 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 cobalt hexacyanoferrate powders, graphite carbon powders
and carbon paste were mixed with the appropriate ratio (cobalt hexacyanoferrate :
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
linear range of H2O2 (cobalt hexacyanoferrate : graphite carbon
powders = 3 : 7); At 30 ℃; the operating potential = –200
m V; in 0.1 M KCl of 5 mL 0.05 M PBS buffer solution ( pH= 7.4 );
stirring rate =700 rpm; 10μL of 100mM H2O2 is injected per 100
seconds
0.05 cm
0.5 cm
CONCLUSIONS
The results showed that the responding current for the carbon paste electrode modified with the cobalt hexacyanoferrate 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 -250mV, it caused the detection to be unstable, -200mV operating potential was used in
this research and 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 –200mV operating potential, 700rpm stirring rate and in 0.05M phosphate buffer
solution (pH=7.4), the detection limit was 0.02 mM H2O2, the linear range was 0.02~1.8 mM H2O2, R2=0.9990 and the sensitivity was
181.52 μA/cm2ּmM H2O2. This research can be further applied to the glucose biosensor in the future.
cobalt hexacyanoferrate
Mixing with
Carbon Paste
REFERENCES
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Carbon Powders
2. Uang, Y.-M. ; Chou, T. -C., Biosensors and Bioelectronics, 2003, 19, 141-147.
3. Qian, L. ; Yang, X., Talanta, 2006, 68, 721-727.
4. Yang, X. ; Chen, X. ; Zhang, X .; Yang, W. ; Evans, D. G., Sensors and Actuators B, 2008, 129, 784-789.
DEPARTMENT OF CHEMICAL AND MATERIALS ENGINEERING, SOUTHERN TAIWAN UNIVERSITY