# Comparative Study of the Presence of Heavy Metals in Edible Vegetable Oils
###### Abstract
Currently, the polymers used are highly inert and it is very difficult for them to transfer mass to food; however, there are a number of minority components which comprise chemical molecules below 1000 Daltons and which are transferred quite easily to the product already packaged [9]. One of the heavy metals intrinsically related to the migration phenomenon is antimony (Sb). It is a catalyst used in the polymerization reaction for the formation of containers that tends to decompose during this process. Although it appears as a degradation product, it tends to be volatile and is generally found at very low levels [10]. However, more recent studies agree that Sb is the element that most easily migrates among all substances, from polyethylene terephthalate (PET) to water, through leaching [11]. Sb can be found in two oxidation forms: organic, which is the least toxic; and inorganic, which is the most toxic. As previously mentioned, antimony is used as a catalyst in PET synthesis or polymerization processes, as antimony trioxide (Sb\({}_{2}\)O\({}_{3}\)). In the chemical reaction, it is in charge of increasing the speed and, at the end of it, the excesses of Sb are coupled to the polymer chain forming antimony-glycan complexes, leaving free traces of Sb\({}_{2}\)O\({}_{3}\) and with no links [12]. Additional to the physical-chemical properties of the container, there are other factors that influence the migration of chemical components to food. These are: the characteristics and nature of the food, i.e., liquids or fatty foods when in contact with the container are most likely to be affected by migration due to their greater solubility power; the temperature,increasing the migration process as it increases; and the contact time, the container-food exposure time is proportional to the migration process [13]. Edible vegetable oils, which are the aims of this review, are a growing sector worldwide, with palm and palm kernel oil leading the consumptions with 36.3 and 4.2%, respectively. They are followed by soybean oil with 27.7%, rapeseed oil with 13.5%, and sunflower oil with 9.5% according to the U.S. Department of Agriculture (USDA, Washington, DC, USA) report of June 2019. The above-mentioned oils account for almost 91% of the total production and consumption of vegetable oils. The remaining 9% are olive, corn, or peanut oils, among others, all of them increasing [14]. This review examines the current status of the presence of heavy metals in edible vegetable oils and analyzes the status of current legislation, from 2015 to 2022, in order to improve the quality of oils and consumer protection. The most studied regions, vegetable oils, heavy metals, analytical techniques, and chemical extracting agents for analytes are also investigated, and the most relevant results of the predominant heavy metals are analyzed (Section 2). Finally, the challenges faced by this line of research are exposed (Section 3) and we present the most outstanding conclusions of this work (Section 4). Oils from other matrices were not taken into account, such as: oil from algae [15], crude or virgin vegetable oils unfit for consumption [16; 17; 18; 19; 20], fish oil [21], or oils from other edible vegetables [22].