## 1 Introduction  
_Bixa orellana_ (_Bixa orellana_ L.) is a plant from the Bixaceae family, whose trees are commonly known as _urucam_ or _colorau_[1]. Its fruits are red- or yellow-colored, and the seeds are covered by an arillus rich in carotenoids, such as bixin, used for the production of natural colorings [2] and as body paints by Indigenous people [3]. It has also been used in sacred rituals since ancient times by the First Nations of America [4]. Natural colorings such as bixin are gaining increasing importance [5] due to concerns surrounding the use of some synthetic colorings in food, which are associated with human health risks [6]. The seeds of _Bixa orellana_ are also used for culinary purposes by the Amazonian people, in the form of a powder spice known as _colorico_ or _colorau_[3], which is made by mixing powdered seeds (or its extract) with corn flour, vegetable oil, and salt [7]. The seed without the arillus also has nutritional value, with high amounts of phosphorous, proteins, and amino acids, such as tryptophan and lysine [7, 8]. This plant also has many applications in natural medicine. Nonetheless, there is a shortage of studies related to its medicinal properties, as pointed out in [7]. There is a wide variability in this plant, which propagates through its seeds. Although it is presumed to have a Native American tropical origin [3],due to its many uses, it is currently cultivated in Mexico and South America as well as in tropical and subtropical regions spanning Africa and Asia [9].  
Despite its widespread use, few studies have reported the inorganic composition of the macro- and micronutrients in _Bixa orellana_ fruits and seeds [8; 10; 11]. Notably, the chemical speciation of sulfur (S) remains unexplored. Sulfur plays a critical role in amino acid biosynthesis, coenzyme formation, seed quality maintenance, and germination regulation [12]. Due to its widespread use in the food industry and cosmetics, there is a serious need for fast and reliable techniques to determine its inorganic composition. This is an important requirement for the food industry, in order to determine its nutritional value, and for the cosmetic industry. In the present study, the inorganic composition of _Bixa orellana_ was determined using Wavelength Dispersive X-ray Fluorescence spectrometry. Sulfur chemical speciation was performed using the X-ray Absorption Near-Edge Structure (XANES) technique using synchrotron light. Sulfur is usually taken up from the soil via plant roots in the form of sulfate, undergoing a complex series of reactions. Sulfur is typically present in plants in several oxidation states [13]. From the perspective of a number of important spectroscopic techniques, sulfur is considered a \"silent element\" [14]; however, modern spectroscopic techniques in the X-ray region not only provide information about quantification but can also reveal the oxidation state of sulfur in different plant parts, providing insights into the homeostasis and metabolism of sulfur in different plant tissues. Techniques, such as those used in this study, also require a minimum sample preparation, usually without the need for chemical digestion, extraction, or preparation, which is advantageous for chemical speciation studies since it avoids the risk of any alterations in the constituents. This study is part of a wider study of the macro- and micronutrient compositions of plants from the Amazon rainforest using advanced spectroscopic techniques [15; 16]. The samples considered in this study came from the states of Para and Amazonas in the northern region of Brazil.