10.1002/cctc.201801193
ChemCatChem
FULL PAPER
performed by
a previously established procedure described in our
Competitividade e Internacionalização (POCI), POCI-01-0145-
FEDER-006984 – Associate Laboratory LSRE-LCM, and by
national funds through FCT for PTDC/AAGTEC/5269/2014 and
published works [19-21] from CNT or M/CNT suspensions in
Nafion/water solution. After deposition of the electrocatalytic material on
a Carbon Toray (CT) paper, this last one was glued to the platinum
electrode using conductive carbon cement and dried at room
temperature during 24 h. The cleanness of the surface was tested prior
to each experiment by recording voltammograms in the supporting
electrolyte medium alone.
Centre
of
Chemistry
(UID/QUI/00686/2013
and
UID/QUI/0686/2016).
Keywords: Amoxicillin • electrochemical oxidation •
electrocatalyst based on carbon nanotubes • surface vs.
reactivity relationships
Electrochemical Setup. The voltammetric study was performed in a
thermostated three-electrode glass cell and a two-compartment glass cell
separated by ion exchange membranes (Nafion 117 (Dupond de
Nemours) and Ionac (Sybron Chemicals Inc.). The reference and counter
electrodes were a saturated calomel electrode and platinum foil (99.95%)
respectively. All the potentials are given versus reference hydrogen
electrode (RHE) for easier comparison between different pH media.
Ultra-pure nitrogen (U Quality from Air Liquide) was used to de-aerated
the solutions and to maintain an inert atmosphere over the solutions
during the measurements. The electrochemical instrumentation consisted
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a potentiostat/galvanostat from Amel Instruments coupled to a
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Instruments) and a PCI-MIO-16E-4 I/O module were used for generating
and applying the potential program as well as acquiring data, such as
current intensities.
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Analytical techniques for product analysis
Two chromatographic set-ups were used for the quantitative analysis of
reaction products. The first one consisted of a high performance liquid
chromatograph (HPLC) with an isocratic pump and double on-line
detection including UV-Vis and refraction index detectors, and the
second one an ion chromatography (IC, Dionex) with a conductivity
detector. The separation of reaction products was carried out using
Aminex HPX-87 H (Biorad) and Merck C18 analytical columns for HPLC-
UV and AS11-HC column (Dionex Corp.) for IC. ESI-MS and HPLC-MS
analyses were effectuated using Finnigan Survayor Chromatography
system coupled to LxQ Thermo Mass Detector. The mobile phase was
water with 0.1% acetic acid (solvent A) and acetonitrile (solvent B), at a
flow rate of 0.3 mL/ min. A linear gradient progressed from 10% B (initial
conditions) to 90% B in 15 min and returned to the initial conditions after
5 min. The HPLC system was connected to a linear ion trap mass
spectrometer with an electrospray interface operated under the following
conditions: Mass spectra were acquired in a mass range of 50-500 amu).
The instrument was operated in positive and negative ionization mode,
with capillary voltage of 43 and -49 V, respectively for positive and
negative ionization mode. The mass spectrometry data was handled
using Excalibur software. TOC analyses were carried out by the NPOC
method using a LTOC Total Organic Carbon Analyzer of Shimadzu
coupled to an ASI-L auto sampler of the same brand.
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Acknowledgements
The authors thank FCT (Fundaꢀꢁo para
a Ciꢂncia e a
Tecnologia) for the PhD grant of Marta Ferreira. This work is
also a result of project BioTecNorte (operation NORTE-01-0145-
FEDER-000004) and AIProcMat@N2020 (operation NORTE-01-
0145-FEDER-000006), supported by Norte Portugal Regional
Operational Programme (NORTE 2020), under the Portugal
2020 Partnership Agreement through the European Regional
Development Fund (ERDF). This work also has been funded by
ERDF through COMPETE2020
-
Programa Operacional
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