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We report that glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNTs) can encapsulate or entrap 3,5-dinitrobenzoic acid (35DNB) generating a 35DNB-MWCNTGC electrode. After electrochemical reduction in situ of only one nitro group of 35DNB, it turns into the hydroxylamine derivative (R-NHOH), which can be further oxidized to the nitroso derivative (R-NO). Then, R-NO/R-NHOH redox couple was electrogenerated in situ by cycling the potential between 0.20 and -0.20 V vs Ag/AgCl. The very well-defined and persistent redox couple was characterized with a formal potential, E (o) 'aEuroe= -28 mV vs Ag/AgCl at a scan rate of 20 mV s(-1). Using the Laviron's plot, a transfer coefficient, alpha = 0.45, and an electron transfer rate constant, k (s) = 10.5 s(-1), for the electron transfer of the couple R-NO/R-NHOH, were calculated. This redox reaction results to be a very efficient mediator for electrocatalytic NADH oxidation. The 35DNB-MWCNTGC electrode efficiently catalyzes the oxidation of NADH with a decrease of more than 0.60 V vs Ag/AgCl in the overpotential compared to the bare GCE and a difference of 0.25 V vs Ag/AgCl with respect to the situation without mediator. The preparation of the electrode is very easy and not time-consumingFONDECYT 113016

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A molecularly imprinted polypyrrole polymer-based film and its properties regarding the recognition of gallic acid were investigated. The polypyrrole film was prepared by including a template molecule during the electropolymerisation of pyrrole. The electropolymerisation was performed using cyclic voltammetry in the presence of an aqueous solution of 0.1 M NaClO4 and 0.05 M pyrrole, with and without a template molecule on a glassy carbon electrode. Some of the parameters important to controlling the performance of the polypyrrole were investigated and optimized, including the pyrrole monomer concentration and the electropolymerisation cycles. The modified electrodes were able to detect gallic acid and have been characterized by differential pulse voltammetry and scanning electron microscopy (SEM).