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[Display omitted] • An approach to colorimetric detection of corrosion inhibitors using a portable sensor; • The detection was performed using an Arduino microcontroller photoelectric sensor. • The sensor was able to detect color intensities in the function of the RGB channels; • The colorimetric protocol was based on a reaction of the TBPE and QAs; • As a proof of concept an analysis of a Corton corrosion inhibitor was performed. In this work, we report a complete and portable analytical instrumentation dedicated to the colorimetric analysis of corrosion inhibitors. The construction of the analytical tool was planned based on carousel architecture and it involves a simple combination of a 3D-printed holder containing eight circular zones and an Arduino microcontroller photoelectric sensor. In addition, paper-based analytical devices (PAD) were manufactured in the form of microzones using manual cutting and assembled in the 3D printed holder for performing colorimetric measurements of quaternary amines in wastewater samples from the petroleum industry. A blue dye was used as a model color and the obtained pixels responses through the proposed analytical tool and well-known smartphone-based analysis revealed similar colorimetric intensities, thus clearly demonstrating the high performance of the 3D-printed analytical instrumentation. The target colorimetric reaction occurs via the interaction of ammonium quaternary present in corrosion inhibitors composition with the chromogen 3′, 3″, 5′, 5″ – tetrabromophenolphthalein-ethyl-ester (TBPE) in an acidic medium. Detailed optimization of the colorimetric reaction involving the ammonium quaternary was successfully performed, as well as the evaluation of possible physical–chemical interferences (pH, carbonate levels, and temperature) mostly usual in produced water from petroleum pipelines. Recovery studies of ammonium quaternary in real produced water samples exhibited acceptable performance (88 to 121%). Thus, the obtained results successfully demonstrated that the proposed 3D-printed analytical system associated with PADs offers a huge potential to be used for colorimetric detection of corrosion inhibitors in wastewater samples and it can be used in the point-of-need involving the petroleum industry field. [ABSTRACT FROM AUTHOR]