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Mesoporous Silica Thin Films for Improved Electrochemical Detection of Paraquat
journal contribution
posted on 2018-01-17, 00:00 authored by Tauqir Nasir, Grégoire Herzog, Marc Hébrant, Christelle Despas, Liang Liu, Alain WalcariusAn
electrochemical method was developed for rapid and sensitive
detection of the herbicide paraquat in aqueous samples using mesoporous
silica thin film modified glassy carbon electrodes (GCE). Vertically
aligned mesoporous silica thin films were deposited onto GCE by electrochemically
assisted self-assembly (EASA). Cyclic voltammetry revealed effective
response to the cationic analyte (while rejecting anions) thanks to
the charge selectivity exhibited by the negatively charged mesoporous
channels. Square wave voltametry (SWV) was then used to detect paraquat
via its one electron reduction process. Influence of various experimental
parameters (i.e., pH, electrolyte concentration, and nature of electrolyte
anions) on sensitivity was investigated and discussed with respect
to the mesopore characteristics and accumulation efficiency, pointing
out the key role of charge distribution in such confined spaces on
these processes. Calibration plots for paraquat concentration ranging
from 10 nM to 10 μM were constructed at mesoporous silica modified
GCE which were linear with increasing paraquat concentration, showing
dramatically enhanced sensitivity (almost 30 times) as compared to
nonmodified electrodes. Finally, real samples from Meuse River (France)
spiked with paraquat, without any pretreatment (except filtration),
were analyzed by SWV, revealing the possible detection of paraquat
at very low concentration (10–50 nM). Limit of detection (LOD)
calculated from real sample analysis was found to be 12 nM, which
is well below the permissible limits of paraquat in drinking water
(40–400 nM) in various countries.