Highly sensitive amperometric detection of drugs and antioxidants on non-functionalized multi-walled carbon nanotubes: Effect of metallic impurities?

•Increase in voltammetric and amperometric signals on non-functionalized (NF-) MWCNTs.•EIS data indicated higher activity of NF-MWCNTs and ICP-MS determined 0.1% of Fe+Co.•Functionalization with HNO3/H2SO4 decreased electroactive area and eliminated all metals.•Higher electroactive area combined wit...

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Bibliographic Details
Published in:Electrochimica acta 2017-06, Vol.240, p.80-89
Main Authors: Stefano, Jéssica S., Rocha, Diego P., Dornellas, Rafael M., Narciso, Laiz C.D., Krzyzaniak, Sindy R., Mello, Paola A., Nossol, Edson, Richter, Eduardo M., Munoz, Rodrigo A.A.
Format: Article
Language:English
Subjects:
Antioxidants
Batch-injection analysis
Carbon nanotubes
Catechol
Cobalt
Dopamine
Drugs
Electrical measurement
Electrocatalysis
Electrochemical impedance spectroscopy
Electrochemistry
Gallic acid
Hydroquinone
Impurities
Iron
Measurement
Multi wall carbon nanotubes
Nanotubes
Residual metals
Sensors
Spectroscopic analysis
Structural defect
Widening
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Summary:•Increase in voltammetric and amperometric signals on non-functionalized (NF-) MWCNTs.•EIS data indicated higher activity of NF-MWCNTs and ICP-MS determined 0.1% of Fe+Co.•Functionalization with HNO3/H2SO4 decreased electroactive area and eliminated all metals.•Higher electroactive area combined with residual metals may explain improved responses.•Nanomolar detection of omeprazole and ciprofloxacin on non-functionalized MWCNTs. This work demonstrates that the electrochemistry of different molecules of pharmaceutical interest, including omeprazole, ciprofloxacin, dopamine, catechol, hydroquinone, and the antioxidants tert-butylhydroquine, gallic acid, propyl gallate, and pyrogallol, is affected by the functionalization of multi-walled carbon nanotubes (MWCNTs). Voltammetric and amperometric measurements confirmed the improved analytical characteristics of the GCE modified with non-functionalized (NF) MWCNTs (as-received) in comparison with functionalized MWCNTs (F-MWCNTs). Increase in voltammetric responses (up to 10-fold), higher slope values for the amperometric detection of the analytes (up to 7-fold) and, for some molecules, widening of the linear working range, were verified. Electrochemical impedance spectroscopy measurements also revealed higher electrochemical activity of non-functionalized MWCNTs. The presence of metallic impurities on NF-MWCNTs, removed by functionalization with HNO3/H2SO4, may contribute the improved performance of NF-MWCNT-modified electrodes; however, decrease in electroactive area of F-MWCNTs has to be considered. Although acid functionalization introduced oxygenated groups on the MWCNT structure, the presence of metallic impurities (Fe and Co) and higher electroactive area of NF-MWCNTs play major role on the increase in sensitivity of the electrochemical sensors. As a conclusion, we propose the use of pristine MWCNTs to produce more sensitive amperometric sensors.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2017.04.050