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We show that fused deposition modelling (FDM) 3D-printed electrodes can be used for quality control of fuel bioethanol. 3Dprinting using carbon black/polylactic acid (CB-PLA) filaments resulted in conductive and biodegradable electrodes for biofuel analysis. As a proof-of-concept, copper determination in fuel bioethanol was performed, as such ions catalyse oxidation processes during storage and transport. Square-wave anodic-stripping voltammetry (SWASV) of copper was achieved after sample dilution in 0.1 mol L −1 HCl as supporting electrolyte (resulting in 30:70% v/v ethanol:water). The linear responses were in the range between 10 and 300 μg L −1 (R = 0.999), inter-day precision was lower than 8% (n = 10, for 20 μg L −1 ) and limits of detection (LOD) and quantification (LOQ) using 180 s as deposition time were 0.097 μg L −1 and 0.323 μg L −1 , respectively. Recovery values between 95 and 103% for the analysis of bioethanol spiked with known amounts of copper were obtained. These results show great promise of the application of 3D-printed sensors for the quality control of biofuels.

This review addresses the use of screen-printed electrodes (SPEs) coupled to flow systems such as flow injection analysis (FIA), batch injection analysis (BIA), and high-performance liquid chromatography (HPLC) systems over the last six years (since 2014). The combination of SPEs and flow systems is a powerful synergy to increase the throughput of measurements, improve electrode lifetime, and reduce reagent consumption and waste generation. Recently, commercial flow cells for SPEs were made available by different companies and potential new users that are unable to construct homemade electrochemical flow cells have been attracted to work in the area. This overview aims to show both trends and future potential for the development of new methods useful for modern electroanalysis and/or portable applications.

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This work presents a portable electrochemical system for the continuous monitoring of corrosion inhibitors in a wide range of matrices including ethanol, seawater and mineral oil following simple dilution of the samples. Proof-of-concept is demonstrated for the sensing of 2,5-dimercapto-1,3,5-thiadiazole (DMCT), an important corrosion inhibitor. Disposable screen-printed graphitic electrodes (SPGEs) associated with a portable batch-injection cell are proposed for the amperometric determination of DMCT following sample dilution with electrolyte (95% v/v ethanol + 5% v/v 0.1molL HSO solution). This electrolyte was compatible with all samples and the organic-resistant SPGE could be used continuously for more than 200 injections (100µL injected at 193µLs) free from effects of adsorption of DMCT, which have a great affinity for metallic surfaces, and dissolution of the other reported SPGE inks which has hampered prior research efforts. Fast (180h) and precise responses (RSD < 3% n = 10) with a detection limit of 0.3µmolL was obtained. The accuracy of the proposed method was attested through recovery tests (93-106%) and the reasonable agreement of results of DMCT concentrations in samples analyzed by both proposed and spectrophotometric (comparative) methods.