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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]

[Display omitted] • Use of napkin paper for production of low-cost analytical devices is reported. • New stamping method for creation of paraffin hydrophobic barriers is described. • Novel method for colorimetric quantification of ethanol in beverages is presented. • Analytical application for analysis of real samples is successfully demonstrated. • Results showed great concordance when compared to UV–vis spectrophotometry. In this work we report for the first time the use of napkin paper as substrate for production of paper analytical devices (PADs). Napkin paper is a more accessible and cheaper option compared to the most commonly used chromatographic and filter papers. The PADs were easily fabricated by depositing hydrophobic paraffin barriers using a simple stamping contact method. The stamps used here were fabricated by 3D printing. To the best of our knowledge, this is the first report of this stamping approach aiming production of paraffin barriers in PADs. The PADs proposed here were utilized for colorimetric determination of alcohol content in beverages. This method was based on the redox reaction between ethanol and dichromate in acidic medium. As far as we know, this is the first PAD-based method exploring this principle. The image-based method showed a linear range between 0 and 50 % (v/v) ethanol, with a limit of detection of 1.5 %. This concentration range allows the analysis of various alcoholic beverages. The results obtained during the analysis of real samples presented great concordance with the values found by UV–vis spectrophotometry, used for validation (relative error < 5 %). Thus, the new PAD-based colorimetric method reported here shows great potential for applications in areas such as food control and forensics. Moreover, the use of napkin paper for fabrication of PADs appears to be a promising, easier and less expensive option, being specially interesting for places with limited resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • First coupling of BIA systems to electrochemical paper analytical devices (ePADs). • To adapt the ePAD, a new semi-transparent BIA cell was developed using 3D-printing. • This platform was used for amperometric detection of 5-hydroxytryptophan (5-HTP). • First BIA-based method for 5-HTP analysis. • Real samples were analyzed and the results validated with UV–vis spectrophotometry. This work reports, for the first time, the association of electrochemical paper analytical devices (ePADs) with batch injection analysis (BIA) systems. The novel 3D-printed BIA cell utilized here is semi-transparent (3D-printed by SLA/DLP technology), while the three-electrode paper device was fabricated by pencil drawing. This ePAD/3D-BIA platform was employed for the amperometric detection of 5-hydroxytryptophan (5-HTP). To the best of our knowledge, this is the first BIA method for determining this analyte. The parameters of the method were studied and optimized. The ePAD/3D-BIA system presented good repeatability and reproducibility, with relative standard deviations (RSDs) < 5%, besides high analytical frequency (180 injections per hour). In addition, the ePAD showed excellent performance and lifetime, being able to be utilized for up to eight consecutive days. Under the best conditions, amperometric response of 5-HTP provided linearity in the range of 0.165 to 150 µmol L−1, with a limit of detection (LOD) of 50 nmol L−1. As a proof of principle, the ePAD/3D-BIA was used to analyze 5-HTP in commercial food/pharmaceutical samples. The results presented great precision (RSD ≤ 1.5%) and agreement with the values obtained by UV–vis spectrophotometry (95% confidence level). These findings show the potential of the novel system proposed here. The ePAD/3D-BIA proved to be an efficient, fast and reliable platform that can be a useful tool for the analysis of electroactive species. Moreover, the very low cost, practicality and simplicity may offer interesting advantages over conventional BIA systems. [ABSTRACT FROM AUTHOR]

A limitless-length flexible active-matrix implies that virtually any surface can be rendered into an interactive medium when laminated with electrophoretic or organic light-emitting diode sheets. However, performance, cost, and size limitations of current fabrication technologies and semiconducting materials, typically utilized in thin film transistor (TFT) active matrices (TFT-AMs), have hindered progress, thus preventing the realization of fully printed TFT-AMs on a plastic roll. A new high-purity semiconducting single-walled carbon nanotube (s-SWCNT) ink is prepared by first isolating 99.9% pure s-SWCNTs via conjugated polymer extraction, and then utilizing a ligand-exchange method to formulate a novel hydrophilic gravure-compatible semiconducting ink. Based on the s-SWCNT ink, a fully additive manufacturing process using roll-to-roll (R2R) gravure printing enables the fabrication of a flexible TFT-AM, overcoming performance, cost, and size limitations. TFT-AMs with 10 to 40 PPI resolution where average mobility of 0.23 ± 0.12 cm2 V−1 s−1, average on–off ratio of 104.1, and threshold voltage variation of ±13% are attained. As a proof of concept, an inexpensive and flexible electrophoretic display is demonstrated by simply laminating an electrophoretic sheet onto the R2R gravure-printed s-SWCNT-based TFT-AM.