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Browsing by Author "Brett, C. M. A."

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  • Carbon nanotube β-cyclodextrin-modified electrode for quantification of cocaine in seized street samples
    Publication . Garrido, Jorge; Borges, F.; Brett, C. M. A.; Garrido, E. Manuela
    Detection and quantification of cocaine is a key tool in fields such as police apprehensions and the fight against drug trafficking. Thus, a simple, fast and inexpensive electroanalytical methodology for the determination of cocaine in seized street samples has been developed, employing linear sweep voltammetry. The method is based on the use of a glassy carbon (GC) electrode modified by a combination of multi-walled carbon nanotubes (MWCNT) with β- cyclodextrin (β-CD) incorporated in a polyaniline film. The proposed method shows high reproducibility, repeatability and specificity. Under optimal conditions, the β-CD/ MWCNT-modified GC electrode gives a detection limit of 1.02 μM cocaine. The results obtained are in good agreement with those obtained by the high-performance liquid chromatography reference method. The new methodology proposed has excellent potential as the basis of a portable analytical sensor for on-site screening of cocaine in seized street samples.
    2016Journal article Restricted access Show more
  • Electrochemical sensor for simultaneous determination of herbicide MCPA and its metabolite 4-chloro-2-methylphenol. Application to photodegradation environmental monitoring
    Publication . Rahemi, V.; Garrido, J. M. P. J.; Borges, F.; Brett, C. M. A.; Garrido, E. M. P. J.
    The development and application of a polyaniline/carbon nanotube (CNT) cyclodextrin matrix (PANI-β-CD/MWCNT)-based electrochemical sensor for the quantitative determination of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) and its main transformation product 4-chloro-2-methylphenol in natural waters are described. A simple cyclic voltammetry-based electrochemical methodology, in phosphate buffer solution at pH 6.0, was used to develop a method to determine both MCPA and 4-chloro-2-methylphenol, without any previous extraction or derivatization steps. A linear concentration range (10 to 50 μmol L−1) and detection limits of 1.1 and 1.9 μmol L−1, respectively, were achieved using optimized cyclic voltammetric parameters. The proposed method was successfully applied to the determination of MCPA and 4-chloro-2-methylphenol in natural water samples with satisfactory recoveries (94 to 107 %) and in good agreement with the results obtained by an established high-performance liquid chromatography technique, no significant differences being found between the methods. Interferences from ionic species and other herbicides used for broad-leaf weed control were shown to be small. The newly developed methodology was also successfully applied to MCPA photodegradation environmental studies.
    2015Journal article Restricted access Show more