Determination of Hormone 17 <i>β</i> ‐Estradiol Using Graphite‐Acrylonitrile Butadiene Styrene Electrode Coupled to User‐Friendly 3D‐Printed Batch Injection Analysis Cell

17 β ‐estradiol (E2) is the main female sex hormone widely found in pharmaceutics indicated for contraception and replacement therapy. Because this hormone is secreted by the body and contaminates the aquatic environment, it is considered an important organic pollutant to monitor due to its action on the human body as an endocrine disruptor. Therefore, the development of rapid, sensitive, precise, and portable methods is relevant for its quantification “in situ” in different matrices. In this context we propose the determination of E2 using a fast low‐cost system composed of a graphite‐acrylonitrile butadiene styrene (coated on 3D‐printed ABS substrate) electrode assembled in a novel user‐friendly 3D‐printed batch injection analysis system with amperometric detection (BIA‐AD). The best electrochemical behavior was obtained in 0.04 mol L −1 Britton‐Robinson buffer (pH 3.0) in which an irreversible oxidation was noted at +0.85 V. Under the optimized conditions of BIA‐AD (detection potential = +1.1 V, injection volume = 100 µL, dispensing rate = 142 µL s −1 ), a sensitivity of 0.154 µA µmol −1 L, a linear range of 0.1–7.0 µmol L −1 , an experimental LOD of 0.1 µmol L −1 , and an analytical frequency of 240 injections per hour were obtained. Good precision was reached for sequential injections of E2 at three concentration levels (8.6%, 3.2%, and 5.0% for 0.5, 3.0, and 6.0 µmol L −1 , respectively). Moreover, good interelectrode reproducibility was reached (RSD = 5.5%; n = 4), which confirms good manufacturing efficiency. The method was applied for the determination of E2 in pharmaceutical sample and river water. The results found in a pharmaceutical sample were statistically similar to the obtained by a UV–vis spectrophotometric method. The value found in river water was below the experimental LOD. Thus, this sample was fortified with different concentrations of E2, obtaining recoveries between 100% and 116%, which confirms the good accuracy of the method. The proposed BIA‐AD is promising for the fast on‐site determination of E2 in different matrices.