This document describes a study that modified electrodes with chitosan and platinum nanoparticles for rapid detection of Escherichia coli bacteria. Electrodes were characterized using cyclic voltammetry and atomic force microscopy. The modified electrodes were able to quantitatively determine the presence of E. coli through potentiometric measurements in sodium sulfate solution. The GC/CTS/PtNP electrode prepared at a 50mV/s scan rate provided the best results, with a linear response between potential and log concentration of bacteria. The modified electrodes allow for rapid, quantitative detection of E. coli.

1. MODIFIED ELECTRODES WITH CHITOSAN
AND PLATINUM PARTICLES FOR RAPID
DETERMINATION OF Escherichia coli
Lucy L. Coria Oriundo. Adolfo La Rosa-Toro Gómez.
lcoria@uni.edu.pe – toro@uni.edu.pe
Grupo de Investigación de Electroquímica Aplicada.
Universidad Nacional de Ingeniería. Lima – Perú.
64th Annual Meeting of International Society
of Electrochemistry

2. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
INTRODUCTION
Chitosan
Platinum Nanoparticles

3. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 1. Cyclic voltammograms for GC/Pt electrode in 2mM
H2PtCl6.6H2O solution and 0.5M H2SO4 solution (scan rate: 50mV/s). In
sito shows the stabilized voltammogram for GC electrode at the same
conditions.
-0.3 0.0 0.3 0.6
-5
0
5
j(mA/m
2
)
E vs. Ag/AgCl (V)
0.0 0.7 1.4
-4
0
4
j(mA/m
2
)
E vs. Ag/AgCl (V)
ELECTRODEPREPARATIONAND
MODIFICATION

4. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 2. Cyclic voltammograms for GC/CTS/Pt electrode in 2mM
H2PtCl6.6H2O solution and 0.5M H2SO4 solution (scan rate: 50mV/s). In
sito shows the stabilized voltammogram for GC electrode at the same
conditions.
-0.3 0.0 0.3 0.6
-8
0
8
j(mA/m
2
)
E vs. Ag/AgCl (V)
0.0 0.7 1.4
-4
0
4
j(mA/m
2
)
E vs. Ag/AgCl (V)
ELECTRODEPREPARATIONAND
MODIFICATION

5. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 3. Stabilized voltammograms for GC/CTS electrode in 0.5M
H2SO4 solution. In sito shows the stabilized voltammogram for GC
electrode to 100mV/s
0.0 0.7 1.4
-2
-1
0
1
2
CTS/GC 100mV/s
CTS/GC 50mV/s
j(mA/m
2
)
E vs. Ag/AgCl (V)
0.0 0.7 1.4
-4
0
4
j(mA/m
2
)
E vs. Ag/AgCl (V)
CHARACTERIZATIONOFELECTRODES

6. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 4. Peak current against square root of scan rate for GC/CTS
electrode.
CHARACTERIZATIONOFELECTRODES
4 8 12
20
40
60
80ip
(uA)
v
1/2
(mV.s
-1
)
1/2
Equation y = a + b*x
Adj. R-Square 0.99242
Value Standard Error
B Intercept 0.14723 2.48134
B Slope 5.57196 0.24332

7. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 5. Stabilized voltammograms for GC/Pt electrode in 0.5M
H2SO4 solution. In sito shows the stabilized voltammogram for Pt
polycristaline. (scan rate: 100mV/s)
CHARACTERIZATIONOFELECTRODES
0.0 0.7 1.4
-8
0
8
j(mA/m
2
)
E vs. Ag/AgCl (V)
0.0 0.7 1.4
-20
-10
0
10
j(mA/m
2
)
E vs. Ag/AgCl (V)

8. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
Figure 6. Stabilized voltammograms for GC/CTS/Pt electrode in 0.5M
H2SO4 solution. In sito shows the stabilized voltammogram for Pt
polycristaline. (scan rate: 100mV/s)
CHARACTERIZATIONOFELECTRODES
0.0 0.7 1.4
-40
-20
0
20j(mA/m
2
)
E vs. Ag/AgCl (V)
0.0 0.7 1.4
-20
-10
0
10
j(mA/m
2
)
E vs. Ag/AgCl (V)

9. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
CHARACTERIZATIONOFELECTRODES
Electrode
Real Surface area
(cm2)
GC/Pt 0.16
GC/CTS/Pt 1.18
Figure 7. Stabilized voltammograms for GC/CTS/Pt and GC/Pt
electrodes in 0.5M H2SO4 solution. (scan rate: 100mV/s)

10. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
CHARACTERIZATIONOFELECTRODES
Figure 8. AFM images for (a) GC/CTS, (b) GC/Pt and (c) GC/CTS/Pt
electrodes.

11. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
ELECTROCHEMICALRESPONSE
Figure 9. System analysis for determination of Escherichia coli.
R E
E L
F E
E C
R T
E R
N O
C D
E E
M E
O L
D E
I C
F T
I R
E O
D D
E

12. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
ELECTROCHEMICALRESPONSE
0 1 2 3
360
370
380
390E(mV)
Log UFC (u.a)
Equation y = a + b*x
Adj. R-Square 0.9898
Value Standard Error
E Intercept 362.52292 0.68071
E Slope 10.71231 0.44351
Figure 10. Calibration curves for GC/CTS/PtNPs electrode in
presence of different concentrations of Escherichia coli.

13. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
ELECTROCHEMICALRESPONSE
Table 1.Comparison between both first and second assays for all
modified electrodes.
Electrode
1° Assay 2° Assay
Intercept Slope R2 Intercept Slope R2
GC 224.26 17.585 0.95351 220.35 17.474 0.95904
GC/CTS 252.39 18.850 0.98390 250.66 18.807 0.97970
GC/PtNPs (10mV/s) 357.25 1.4203 0.95452 357.08 1.5075 0.97581
GC/PtNPs (30mV/s) 431.31 10.019 0.96417 431.27 10.011 0.97413
GC/PtNPs (50mV/s) 358.02 6.8986 0.97486 357.89 6.8250 0.97707
GC/CTS/PtNPs
(10mV/s)
384.85 13.072 0.99277 379.36 13.084 0.99431
GC/CTS/PtNPs
(30mV/s)
296.08 8.9565 0.98896 292.83 8.8956 0.99011
GC/CTS/PtNPs
(50mV/s)
368.19 10.850 0.98863 362.52 10.712 0.98980

14. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
EXPERIMENTAL AND RESULTS
ELECTROCHEMICALRESPONSE
Figure 11. Potenciommetric response of GC/CTS/PtNPs electrode in
presence of low and in excess concentrations of Escherichia coli.
0 2000 4000
360
370
380
390
E(mV)
E. Coli (UFC)

15. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
CONCLUSIONS
 Modified electrodes with chitosan and PtNPs (different
scan rates) were prepared and characterized by cyclic
voltammetry and AFM.
 Modified electrodes were used to determinate
cuantitatively presence of Escherichia coli by
Potenciommetric method in sodium sulphate solution.
 The results were compare with GC electrode, and to
different assay, obtaining better results for
GC/CTS/PtNPs prepared with 50mV/s scan rate.

16. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
GRUPO DE INVESTIGACIÓN DE
ELECTROQUÍMICA APLICADA

17. 64th Annual Meeting of International Society of
Electrochemistry
10/09/2013Grupo de Investigación de Electroquímica Aplicada. UNI – FC. Lima, Perú
ACKNOWLEDGEMENTS
CONSEJO NACIONAL DE CIENCIA Y TECNOLOGÍA
(CONCYTEC)
INSTITUTO PERUANO DE ENERGÍA NÚCLEAR
FACULTAD DE CIENCIAS – UNIVERSIDAD
NACIONAL DE INGENIERÍA