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Abstract
The electrochemical detection of carbaryl at low potentials, in order to avoid matrix
interferences, is an important challenge. This study describes the development, electrochemical
characterization and utilization of a glassy carbon (GC) electrode modified with multi-wall
carbon nanotubes (MWCNT) plus cobalt phthalocyanine (CoPc) for the quantitative determination
of carbaryl in natural waters. The surface morphology was examined by scanning electron
microscopy, enhanced sensitivity was observed with respect to bare glassy carbon and
electrocatalytic effects reduced the oxidation potential to +0.80 V vs. SCE in acetate
buffer solution at pH 4.0. Electrochemical impedance spectroscopy was used to estimate
the rate constant of the oxidation process and square-wave voltammetry to investigate
the effect of electrolyte pH. Square-wave voltammetry in acetate buffer solution at
pH 4.0, allowed the development of a method to determine carbaryl, without any previous
step of extraction, clean-up, or derivatization, in the range of 0.33-6.61 micromol
L(-1), with a detection limit of 5.46+/-0.02 nmol L(-1) (1.09+/-0.02 microg L(-1))
in water. Natural water samples spiked with carbaryl and without any purification
step were successfully analyzed by the standard addition method using the GC/MWCNT/CoPc
film electrode.