## 1 Introduction  
Bisphenol A (BPA), one of the most produced and used chemicals, has been widely used for preparing industrial polymers, such as polycarbonate, epoxy resin, and thermosensitive paper [1]. Furthermore, it is often involved in various food contact materials (i.e., canned packaging, bottles, and lacquer coating). Its widespread usage, especially in these food contact materials, has inevitably lead to its exposure to human beings via food and drinking water [2, 3]. As an endocrine-disrupting chemical (EDC) [4, 5], it can destroy natural or synthetic compounds with endocrine function by simulating or blocking endogenous hormones [6]. To date, a temporary tolerable daily intake (t-TDI) of 4 ug kg\({}^{-1}\) b.w. day\({}^{-1}\) for BPA has been proposed by the European Food Safety Authority (EFSA) [7]. Legislation against BPA usage in some infant food package and bottles has also been enacted, in many countries all over the world [8].  
For monitoring the pollution levels and ecological risks of BPA, many methods based on capillary electrophoresis [9, 10, 11], gas chromatography coupled with mass spectrometry (GC-MS) [12, 13, 14, 15], high performance liquid chromatography mass spectrometry (LC-MS) [16, 17], enzyme linked immune sorbent assay (ELISA) [18, 19, 20], and electrochemical methods [21, 22, 23, 24] have been developed. Pretreatment procedures, such as solid-phase extraction [25, 24, 26], liquid-liquid extraction [27, 28], and immunoaffinity chromatography [29, 30], are often involved when using GC-MS, HPLC-MS, and ELISA for analyzing BPA in complex matrices [31, 32]. Although these common methods can't do without complementary pretreatments and expensive equipment, they are still the reliable strategies for analyzing environmental BPA.  
Compared with the methods mentioned above, electrochemical methods, with the advantages of easy preparation, high sensitivity, simplicity for operators, and in-situ monitoring [33], are often proposed as one of the preferable techniques for routine analysis. In order to analyze trace levels of chemicals, improving the response signals of substances is a vital part of these electrochemical methods. Modification of the electrodes with various functional materials is one of the most recommended strategies. For example, electrodes modified with graphene nanomaterials present excellent electric conductivity as a result of their good conductivity [33; 34; 35]. Molybdenum-selenide (MoSe\({}_{2}\)) electrodes showed much more sensitivity to BPA, as a result of increasing surface active sites [36]. Noble metal oxides, such as RuO\({}_{2}\), PdO, IrO\({}_{2}\), and Rh\({}_{2}\)O\({}_{3}\), are widely used in heterogeneous catalysis systems. Rh\({}_{2}\)O\({}_{3}\) has been proven to be an excellent catalyst for the oxidation of CO [37; 38] and the deposition of H\({}_{2}\)O\({}_{2}\)[39] and N\({}_{2}\)O [40], but it is still rarely reported for sensors.  
In this paper, a Rh\({}_{2}\)O\({}_{3}\)-GO composite nanomaterial was chosen, and a novel electrochemical sensor was fabricated with a modified glassy carbon electrode (GCE) for excellent catalytic performance and conductivity. The modified glassy carbon electrode (GCE), coated with a Rh\({}_{2}\)O\({}_{3}\)-rGO membrane with excellent stability and selectivity, was synthesized and was then used for analyzing BPA dissolved in drinks for the first time after simple filtration.