A novel 3D-printed batch injection analysis (BIA) cell coupled to paper-based electrochemical devices: A cheap and reliable analytical system for fast on-site analysis

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 (3Dprinted 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 mu mol 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.