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Electrochemical Biosensor for Sensitive Quantification of Glyphosate in Maize Kernels
Author(s) -
CahuantziMuñoz Selene L.,
GonzálezFuentes Miguel A.,
OrtizFrade Luis A.,
Torres Eduardo,
Ţălu Ştefan,
Trejo G.,
MéndezAlbores Alia
Publication year - 2019
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.201800759
Subject(s) - biosensor , glyphosate , chemistry , pulmonary surfactant , nuclear chemistry , aqueous solution , chromatography , organic chemistry , biochemistry , agronomy , biology
A graphite‐epoxy electrode (GE) modified with multiwalled carbon nanotubes (MWCNTs) and horseradish peroxidase ( GE/MWCNTs‐HRP) was used to build a glyphosate biosensor whose performance in aqueous solutions depends on the enzyme activity. For the biosensor preparation, MWCNTs were deposited onto the GE surface by electrophoresis using an oxidative treatment (H 2 SO 4 /HNO 3 ) in presence of cetyl tributylammonium bromide (CTAB) as a cationic surfactant. The surfactant was further removed from the MWCNTs surface by dipping the electrode in an EtOH/HCl solution. The physical immobilization of HRP and therefore the glyphosate sensing capabilities was tested at pH 4 where the herbicide exhibits one only species. Circular dichroism studies suggested that the secondary structure of HRP changes as a result of its interaction with glyphosate and that this change is intensified by the combination of glyphosate and H 2 O 2 , which may explain the decrease of the enzyme catalytic activity with the increase of glyphosate concentration. The glyphosate quantification in doped‐maize kernels was highly reproducible and exhibits detection and quantification limits of 1.32 pM and 1.63 pM respectively. The biosensor is also characterized by a high recovery (100 %) and precision (coefficient of variation <1 %) and can be employed in presence of interfering substances such as chlorpyrifos (an organophosphate pesticide) and starch.