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Screen‐printed electrodes have been used for the determination of amino acids, focussing particularly on tryptophan, following different surface modifications by carbon nanotubes (CNT), carbon black (CB) and copper nanoparticles. The modified electrodes were characterised by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. Detection by square wave voltammetry was improved by further surface modification with copper nanoparticles, exhibiting efficient electrocatalytic activity towards amino acid oxidation with high sensitivity, stability and long shelf‐life. The applicability of a low‐cost, robust carbon black substrate using the synergetic electrocatalytic effect provided by copper nanoparticles for amino acid sensing is demonstrated.

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Screen-printing technology is a particularly attractive technique for the mass production of cheap and disposable sensors, and the use of screen-printed electrodes (SPEs) in conjunction with portable, electrochemical instrumention greatly facilitates the feasibility of on-site testing. In this work, a simple, electrochemical method using screen-printed probes has been applied to test for the presence of released lead (Pb) in the glazes of different ceramic tajines collected randomly from a local market square in Morocco. Square-wave anodic voltammetry (SWAV) was employed with SPEs that had been modified with a bismuth film and 5 ml of 0.5% nafion (SPEBi-Na). This probe displayed excellent linear behavior over the examined concentration range, from 5 to 80 mg=L Pb 2þ in 100 mM acetate buffer, pH 5, with a detection limit of 4 ppb for lead and (r 2 ¼ 0.9972). The good reproducibility obtained with this system led us to apply it to determine lead in this typical Moroccan cookware under conditions relevant to its use. The results showed that when tajines containing 3% acetic acid were heated for 30 min, the amounts of leached lead ranged from 16.8 to 26.4 ppm. When the tajines contains lemon instead of 3% acetic acid and was heated for 30 min, then amounts of lead released exceeded 37 ppm. These values are greater than the allowed maximum concentrations in the United States and Canada.

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