Transcript 下載/瀏覽

The pH on the Detection of Hydrogen Peroxide for Electrode Modified with Chromium Hexacyanoferrate
Chen-Hsun Hu (胡真熏) , 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
ABSTRAC
T
Because hydrogen peroxide plays an important role in industry and also because sometimes hydrogen peroxide is used in the food industry for the purpose of preservation , a rapid and convenient sensor for detecting the hydrogen peroxide is an important research subject.
Because the Chromium 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 Coprecipitation method to prepare the Chromium Hexacyanoferrate .
The Chromium Hexacyanoferrate was used to modify the carbon paste electrode [ Chromium 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 Chromium Hexacyanoferrate ( Chromium 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 Chromium 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 pH of buffer solutions
were plotted to evaluate the effect of the pH of buffer solutions 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 0.02～2.8 mM H2O2 , R2 = 0.9999 and the sensitivity was 242.57µA/cm2．mM H2O2.
INTRODUCTION
RESULTS
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. In recent years, the diabetes has become one of the top ten causes of
death for the people in our country. 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, and therefore, as the concentration of hydrogen peroxide
can be determined, the concentration of glucose can also be determined. Because the
Chromium Hexacyanoferrate possesses the excellent catalytic characteristic it can be
used with the carbon paste and carbon powders which possess the high 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 sensitivity of detection of hydrogen peroxide can be
determined. A study of the TB (Time Base) graphs for the carbon paste electrode at
different pH of buffer solutions was conducted to evaluate the effect of pH of buffer
solution on the responding current of detection of hydrogen peroxide.
(A)
(B)
Fig. 1 CV graphs for (A) carbon paste electrode modified
with chromium hexacyanoferrate (Ⅱ) ( 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 pH of buffer solutions (chromium
hexacyanoferrate (Ⅱ) : graphite carbon powders = 3 : 7); the pH
values are [ (A) pH=4 (B) pH=5 (C) pH=6 (D) pH=7.4 (E) pH=8 ]
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 pH of buffer solutions for
the carbon paste electrode modified with chromium
hexacyanoferrate (Ⅱ) [ (A) pH=4 (B) pH=5 (C) pH=6 (D) pH=7.4 (E)
pH=8 ]
Table 1 The sensitivities, responding currents, and R2 values of
different pH of buffer solutions for the carbon paste electrode modified
with chromium hexacyanoferrate (Ⅱ)
2. Chemicals and Reagents:
Chromium Chloride, 6-Hydrate (CrCl3．6H2O) ; Potassium
Hexacyanoferrate(Ⅱ)( K4[Fe(CN)6] ．3H2O ) ; 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 chromium hexacyanoferrate (Ⅱ) powders, graphite carbon
powders and carbon paste were mixed with the appropriate ratio (chromium
hexacyanoferrate (Ⅱ) : 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 (chromium
hexacyanoferrate (Ⅱ) : graphite carbon powders = 3 : 7); At 30
℃; the operating potential = –200m V; in 0.1 M KCl of 5 mL
0.05 M PBS buffer solution ( pH= 7.4 )
Fig. 5 The TB graphs of carbon paste electrodes for determining the
linear range of H2O2 (chromium hexacyanoferrate (Ⅱ) : graphite
carbon powders = 3 : 7); At 30 ℃; the operating potential = –200m
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 TB (Time Base) graphs for the carbon paste electrode at different pH of buffer solutions were plotted to
evaluate the effect of pH of buffer solution on the responding current of detection of hydrogen peroxide. The
results of TB (Time Base) graphs showed that when pH=8 the responding current was the highest. Because
the pH value of human blood is about 7.4, the buffer solution of 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 = 700 rpm, and pH = 7.4. Also the results showed that at –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 0.02~2.8 mM H2O2, R2=0.9999 and the sensitivity was 242.57μA/cm2ּmM H2O2.
chromium hexacyanoferrate
Mixing with
Carbon Paste
REFERENCES
Carbon Powders
1. M. A. Kim and W.-Y. Lee, “Amperometric Phenol Biosensor Based on Sol-Gel Silicate/Nafion Composite Film,” Analytica
Chimica Acta, 479, 143 (2003).
2. L. Qian and X. Yang, “Composite Film of Carbon Nanotubes and Chitosan for Preparation of Amperometric Hydrogen Peroxide
Biosensor,” Talanta, 68, 721(2006).
3. D. Odaci, A. Telefoncu and S. Timur, “Pyranose Oxidase Biosensor Based on Carbon Nanotube (CNT)-Modified Carbon Paste
Electrodes,” Sensors and Actuators B, 132, 159 (2008).
4. L. Shi, X. Liu, W. Niu, H. Li, S. Han, J. Chen and G. Xu, , “Hydrogen Peroxide Biosensor Based on Direct Electrochemistry of
Soybean Peroxidase Immobilized on Single-Walled Carbon Nanohorn Modified Electrode,” Biosensors and Bioelectronics, 24,
1159 (2009).
DEPARTMENT OF CHEMICAL AND MATERIALS ENGINEERING, SOUTHERN TAIWAN UNIVERSITY