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NEW RESULTS AND DISCUSSION OF THE
ELECTROCATALYTIC REDUCTION OF ORGANOHALIDES BY
MYOGLOBIN, HEMOGLOBIN AND HEMIN IN
BIOMEMBRANE- LIKE FILMS AND ITS APPLICATION TO
THE ELECTROCHEMICAL DETECTION OF
POLLUTANTS Alejandro ALATORRE and Fethi BEDIOUI
Laboratoire d Électrochimie et Chimie
Analytique UMR n 7575 du CNRS, École Nationale
Supérieure de Chimie de Paris, 11 rue Pierre et
Marie Curie 75231 Paris Cedex 05, France.
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INTRODUCTION
In this study, we go into the examination and the
discussion of the possible use of myoglobin (Mb),
hemoglobin (Hb) and Hemin embedded in
didodecyldimethylammonium bromide (DDAB) films as
potential materials for the effective
electrochemical detection of trichloroacetic
acid, ethylene dibromide, tetrachloroethylene,
trichloroethylene, dichloro-acetic acid,
p-dichlorobenzene, bromodichloromethane,
hexachlorobenzene and hexachlorocyclo-pentadiene
in aqueous solution. Our descriptive results of
the electrocatalytic behavior of DDAB/Mb, DDAB/Hb
and DDAB/Hemin films constitute a first
important step in the investigation of the
evaluation of a strategy materializing the use
of these biomaterials for the reductive detection
of various significant organohalide
derivatives. They also raise, for the first
time, the fact that the examined materials suffer
from slight passivation process revealed during
the electrochemical measurements. In addition,
the sensitivity of the examined DDAB/Mb and
DDAB/Hb biomembranes still be relatively poor,
compared to that of DDAB/Hemin, in the case of
tri- and dichloroacetic acid detection.
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AIM OF THE STUDY
(1)
Characterization of the redox and
electrocatalytic properties of Mb, Hb and Hemin
incorporated in DDAB film
FeII
FeIII
- 1.10
- 0.15
E (V/SCE)
FeII
FeI
or
RXn
RXn
RXn-1 X-
RXn-1 X-
(2)
Application to the electrochemical detection of
organohalides RX
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EXPERIMENTAL
H2O
vesicle
Formation of an homogeneous DDAB vesicle
dispersion
Ultrasonication of DDAB in aqueous solution
Addition of Mb, Hb or Hemin
1- Deposition of a drop of the DDAB/biomolecule
mixture
2- Evaporation of the aqueous solution
HOPG or VC Electrode
Mixture of DDAB vesicle dispersion catalyst
(Mb, Hb or Hemin)
Formation of a DDAB/Mb, Hb or Hemin film on the
electrode surface.
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Electrochemical characterization of DDAB/Mb, Hb
and Hemin films
Myoglobin, Mb
Orientation of the heme center at 600
Hemoglobin (Hb)
DDAB bilayers
Myoglobin (Mb)
Electrode
Hemin (Hn)
From Rusling and coll. J. Phys. Chem. 99
(1995) 11013-11017.
Cyclic voltammograms of modified electrodes ()
(A) HOPG/DDAB-Hb film (area 1 cm2) (B)
HOPG/DDAB-Mb film (area 1 cm2) and (C)
VC/DDAB-Hn (area 0.07 cm2) and unmodifiede
electrodes (-----) in aqueous acetate buffer
solution containing 50 mM NaBr (pH 5.6) at v
100 mV/s).
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Electrocatalytic reduction of organohalides by
DDAB/Mb, Hb and Hemin films
Cyclic voltammogram (v 100 mV/s) of 5 mM TCA in
aqueous solution (pH 5.6) at HOPG/DDABMb
modified electrode (curve 1) and HOPG/DDAB
modified electrode (curve 2).
Cyclic voltammogram (v 100 mV/s) of 10 mM TCE
in aqueous solution (pH 5.6) at HOPG/DDABHb
modified electrode (curve 1) and HOPG/DDAB
modified electrode (curve 2).
Cyclic voltammogram (v 100 mV/s) of 10 mM PCE
in aqueous solution (pH 5.6) at HOPG/DDABHemin
modified electrode (curve 1) and HOPG/DDAB
modified electrode (curve 2).
vitreous carbon electrode HOPG electrode
square wave Voltammetry cyclic voltammetry
Icat catalytic current DCA dichloroacetic
acid TCA trichloroacetic acid PCE
tetrachloroethylene TCE trichloroethylene EDB
ethylene dibromide BDCM bromodichloromethane HC
CPD hexachlorocyclopentadiene DCB
p-dichlorobenzene HCB hexachlorobenzene.
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Electrocatalytic reduction of organohalides by
DDAB/Mb, Hb and Hemin films
It should be noted that the sensitivity of the
examined DDAB/Hemin film towards TCA and DCA is
much higher than that for DDAB/Mb and DDAB/Hb
biomembranes (2 to 21 times higher).
f
B
A
DCA 0.0 mM DCA 0.2 mM DCA 0.4
mM DCA 0.6 mM DCA 0.8 mM DCA 1.0 mM
DCA 0.0 mM DCA 1.0 mM DCA 2.0
mM DCA 3.0 mM
Square wave voltammograms of (A) DDAB/Hemin and
(B) DDAB/Mb modified vitreous carbon electrode in
aqueous acetate buffer solution 50 mmol.L-1
NaBr (pH 5.6) containing DCA and various
concentrations
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Discussion Conclusion
1- The electrocatalytic reduction currents of (i)
TCA and DCA, (ii) TCA, DCA and PCE, and (iii) TCA
and PCE generated over DDAB/Hemin , DDAB/Mb and
DDAB/Hb modified electrodes, respectively are
found to be directly proportional to the
concentration of the organohalides in
solution. 2- In the case of TCE, PCE and EDB a
sligth passivation of the modified electrode was
observed during repeated potential scanning.
Irreversible passivation was observed with BDCM
and HCCPD. Such passivation complications suggest
that the reduction products of these organic
halides alterate the redox activity of the
complex. 3- No catalytic reduction was observed
for DCB in the same conditions. Our descriptive
results of the electrocatalytic behavior of
DDAB/Hemin, DDAB/Mb and DDAB/Hb films are new and
they constitute one of the rare examples of
application of such molecular materials in this
field. They provide, for the first time, a clear
insight into the investigation of the evaluation
of a strategy materializing the use of these
molecular materials for the detection of various
significant organohalide derivatives in aqueous
solution. This offers future prospects for
coupling such chemically modified electrochemical
sensors with liquid or gas chromatography
analysis. These results also confirm the
potentiality of the examined materials in the
reductive dehalogenation process of organohalide
derivatives.
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