# Application of Microgel as a Sorbent for Bisphenol Analysis in Liquid Food Samples
## 1 Introduction  
Food contamination might be one of the most common methods of hazardous substances being ingested into a human body. One of the sources of food contamination is inadequate packaging, which may result in the migration of chemical compounds [1]. Among these substances are bisphenols, which are often employed in the production of polycarbonate and epoxy resins. These materials are often used to manufacture plastic bottles, internal coating of cans, food containers and microwave oven dishes [2]. BPA release from polycarbonate is explained by two different processes: diffusion-controlled release of residual BPA present in the polymer and hydrolysis, decomposition overtime at the polymer's surface [3]. Special attention should be also paid to plastics marked with recycling codes 3 (polyvinyl chloride) or 7 (other types), as they might be made with BPA or its analogue [4]. Bisphenols are becoming well known as they appear to be aggressive endocrine disruptors, and they can easily migrate from plastic and can containers to food [5]. Endocrine disrupting compounds (EDC) disrupt proper functioning of endogenous hormones by mimicking their actions, which results in interferences with synthesis, transport and metabolism of steroid hormones [6]. Bisphenol A is linked to a variety of reproductive and cardiovascular diseases [4, 7, 8] and the development of many types of cancer (including lung, breast and prostate cancer) [9, 10]. For this reason, since January 2011, the manufacture of baby bottles containing BPA is prohibited in European Union,while, since September 2018, the specific migration limit from plastic packaging for BPA was reduced to 50 \(\upmu\)g\(\cdot\)kg\({}^{-1}\)[11]. These restrictions regarding the use of BPA in plastic containers result in the replacement of BPA with its alternatives. Unfortunately, many of them are also bisphenols with estrogenic activity (BPB, BPS, BPE and BPF) [12; 13; 14]. As it has also been stated in a review article written by [PERSON] et al. [15], although the estimated daily intake rates of bisphenols might be low, the potential additive or synergistic effects produced by a mixture of bisphenol analogues may be dangerous to human health and should be considered in epidemiological studies assessments. Due to these facts, when evaluating the safety of compounds for consumer use, it is essential to consider entire classes instead of individual compounds [16]. Several reviews carefully described analytical methods and sample preparation used for the determination of bisphenols in food [17; 18; 19; 20]. Chromatographic methods such as gas chromatography (GC) or high-performance liquid chromatography (LC) with mass spectrometry are the most often used for the determination of bisphenols. However, due to the complicated matrix and ultra-low concentrations of bisphenols in food [11], samples often require extensive preparation before instrumental analysis. The majority of preconcentration methods used for the extraction of bisphenols from food are based on solid-phase extraction (SPE) [18; 21] or microextraction techniques [22; 23], where molecularly imprinted polymers (MIP) were often used as selective sorbents. One of the novel alternatives of cost-effective sorbent are microgels [24], as their porous structure provides advantages, such as strong mechanical strength and large specific surface area, which can uptake a high concentration of the analyte [25]. As was stated by [PERSON] et al. [26], a major attribution of the usage of microgels is their ability to regenerate and be reused for several cycles. Recently, a few papers presented microgels, which were dedicated as a sorbent for BPA extraction. [PERSON] et al. [27] synthesized a polyethylene glycol diacrylate (PEGDA) hydrogel microsphere via reverse emulsion/UV light polymerization and applied it for the enrichment of BPA in spiked water samples. By applying 10 mg of hydrogel for spiked river samples, they achieved 91% recovery, which confirmed the application of hydrogel in real samples [27].