A new miniaturized flow injection analysis (FIA) system for developing electrochemiluminescence (ECL)-based assays is presented. Novel thin-layer flowÀcell (TLFCL) screen-printed carbon electrodes integrated in one-channel flow cells were used as the electrode surface. These TLFCL electrodes, combined with miniaturized electrochemical and optical instrumentation, allowed a high degree of automation and simplicity of the assay. The performance of this high-throughput flow system was corroborated with a proof-of-concept centered on H 2 O 2 detection. For that purpose, an ECL transduction chemistry mechanism based on a electrochemiluminescence resonance energy transfer (ECL-RET) donorÀacceptor strategy, between an electro-oxidized luminophore (luminol) to a fluorophore (fluorescein), in the presence of the analyte of interest, was carried out. The results showed that fluorescein ECL-RET luminescent response increases the sensitivity of H 2 O 2 detection by up to one order of magnitude, in comparison with a luminolÀH 2 O 2 fluorescein-free assay. All experiments were performed in a decentralized, small-sized, easy-to-use FIA system coupled to ECL detection instrumentation.The light emitted from electrogenerated chemiluminescence (ECL) is a process in which electrochemically generated species combine to undergo electron-transfer reactions to form excited, light-emitting species, giving place to the development of high sensitive and selective assays. [1][2][3][4][5][6][7][8][9][10][11] In order to increase the automation of luminescent analytical procedures, the detection of ECL response by flow injection analysis system (FIA) is an interesting option. [12,13] Flow analysis is characterized by highly reproducible and throughput sampling. In addition, sequential injection analysis allows a considerable reduction in the consumption of the sample and reagents. [14] Bearing in mind that ECL based advances are moving towards the development of portable, high-throughput and point-of-care testing systems, [8,15] disposable screen-printed electrodes coupled to a small-sized, non-conventional, FIA system appears as an attractive possibility.For that purpose, in this work, screen-printed electrodes integrated in one channel flow-cell (TLFCL, Thin layer flow-cell) were used as the electrode surface. In these electrodes a transparent slide, that usefully allows the detection of air bubbles inside the cell, is attached over the screen-printed electrodes platform delimiting a flow channel. The injection of sample volume is done through an "in-line luer" injection port, placed closest to the electrochemical cell, where the injection can be easily controlled by operator through a precise syringe. This configuration brings important advantages since it simplifies operability and effectiveness of working in FIA systems. A similar format was already reported in two previous works [16,17] where enzymatic amperometric based sensors were developed. However, this is the first time that these electrodes, integrated in the necessary accessori...