Transcript 下載/瀏覽

The Effect of Stirring Rate on the Detection of Hydrogen Peroxide for the Carbon Paste Electrode Modified with Chromium
Hexacyanoferrate
Chen-Hsun Hu (胡真熏) , 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
Both the hydrogen peroxide sensor and glucose biosensor are important research subjects. 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 stirring rates were plotted to evaluate the effect of the stirring rate 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
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 chromium hexacyanoferrate (Ⅱ)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 chromium hexacyanoferrate (Ⅱ) [chromium
hexacyanoferrate (Ⅱ) : 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 stirring
rates. The TB (Time Base ) graphs and calibration curves for different stirring rates were plotted to
determine the optimum operating conditions in this research.
(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 stirring rates (chromium hexacyanoferrate (Ⅱ) :
graphite carbon powders = 3 : 7); the stirring rates are [ (A)
300rpm (B) 400rpm(C) 500rpm (D) 600rpm (E) 700rpm ]
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 electrode, 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 stirring rates for the
carbon paste electrode modified with chromium hexacyanoferrate
(Ⅱ) [ (A) 300rpm (B) 400rpm(C) 500rpm (D) 600rpm (E) 700rpm ]
Table 1 The sensitivities, responding currents, and R2 values of
different stirring rates 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 results showed that the responding current for the carbon paste electrode modified with chromium hexacyanoferrate (Ⅱ)
was elevated significantly. The TB (Time Base ) graphs at different stirring rates were plotted to evaluate the effect of the stirring
rate on the responding current of detection of hydrogen peroxide and determine the optimum operating conditions. Because when
the stirring rate was 800 rpm, it caused the detection to be unstable, 700 rpm stirring rate 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 0.02~2.8 mM H2O2, R2=0.9999 and the sensitivity was 242.57 μA/cm2ּmM
H2O2. This research can be further applied to the glucose biosensor in the future.
chromium hexacyanoferrate
Mixing with
Carbon Paste
REFERENCES
1. Pandey, P. C. ; Upadhyay, S., Sensors and Actuators B, 2001, 76, 193-198.
Carbon Powders
2. Uang, Y.-M. ; Chou, T.-C., Biosensors and Bioelectronics, 2003, 19, 141-147.
3. Liu, Y. ; Lei, J. ; Ju, H., Talanta, 2008, 74, 965-970.
4. Qiu, J.-D. ; Zhou, W.-M. ; Guo, J. ; Wang, R. ; Liang, R.-P., Analytical Biochemistry, 2009, 385, 264-269.
DEPARTMENT OF CHEMICAL AND MATERIALS ENGINEERING, SOUTHERN TAIWAN UNIVERSITY