# Application of Microgel as a Sorbent for Bisphenol Analysis in Liquid Food Samples
## 4 Discussion  
For the very first time, the microgel was used as a sorbent in the preconcentration of bisphenols from complicated liquid matrices. The optimized microgel-SPE procedure with further analysis with LC-FLD allowed for 5-fold preconcentration of food samples and obtaining an LOD down to 0.9 ng\(\cdot\)mL\({}^{-1}\) for BPF and BPA, 2.3 ng\(\cdot\)mL\({}^{-1}\) for BPE and 2.9 ng\(\cdot\)mL\({}^{-1}\) for BPB. The high extraction efficiency of microgel for different complex matrices suggests that the developed poly(MEO\({}_{2}\)MA) microgel might be the effective solution for sample preparation in routine analysis of trace BPF, BPE, BPA and BPB. The application of microgel as sorbent resulted in discovering trace concentrations of BPA in five out of the twelve of the analyzed liquid food samples (mandarin, pineapple, peach, pickles and mushroom). The results of the cleanup and the obtained recoveries are comparable to commercial cartridges. Moreover, compared to different methods reported in the literature (listed in Table 4) the obtained limit of detection for BPF and BPA was lower than others who used classical liquid chromatography. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Analyte(s)** & **Sample** & \begin{tabular}{c} **Sample** \\ **Preparation** \\ \end{tabular} & **Determination** & \begin{tabular}{c} **LOD** \\ **[**ng\(\cdot\) L\({}^{-1}\)**]** \\ \end{tabular} & **Ref.** \\ \hline BPF, BPA & honey & MIP & LC-DAD & BPF, BPA 2.0 & [32] \\ \hline BPB, BPA & peeled canted tomatoes & \begin{tabular}{c} (I). Strata C18 \\ (II). Florisil SPE \\ cartridges \\ \end{tabular} & LC-UV/FLD & \begin{tabular}{c} BPB 0.7 \\ BPA 1.1 \\ \end{tabular} & [33] \\ \hline BPB, BPA & tuna & LLE & LC-FLD & \begin{tabular}{c} BPA 1.3 \\ BPB 3.0 \\ \end{tabular} & [34] \\ \hline BPB, BPE & plastic packed baby & \begin{tabular}{c} (I). LLE \\ (II). C18 and PSA \\ SPE cartridges \\ \end{tabular} & GC-MS/MS & \begin{tabular}{c} BPF 0.1 \\ BPB, BPE, BPA, \\ BPS 0.3 \\ \end{tabular} & [12] \\ \hline BPF, BPA, BPB & \begin{tabular}{c} canned \\ energy \\ drinks \\ \end{tabular} & \
\begin{tabular}{c} Affinimip\({}^{\circledR}\) \\ cartridge \\ \end{tabular} & UHPLC-FLD & BPB, BPF, BPA 0.2 & [29] \\ \hline BPF, BPE, BPA, & energy drink, liquid from can (pineapple, mandarin, figs) & Microgel & LC-FLD &
\begin{tabular}{c} BPF, BPA 0.9 \\ BPE 2.3 \\ BPB 2.9 \\ \end{tabular} & This work \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of our method of preconcentration of bisphenols to others. Figure 5: Comparison of our microgel performance with commercial SPE cartridges. Results obtained for fruits in syrup spiked with 50 ug\(\cdot\)L\({}^{-1}\) mixture of four bisphenols. Data are means with RSD (\(t=3\)). It should be noted that the consideration of analyzing bisphenols from a quality assurance perspective require quantitation of bisphenols in both solid and liquid parts of food products. This was also confirmed in the work of [PERSON] et al. [35], where higher amounts of bisphenol A were found in solid parts than liquid part of canned food. This is why further studies are necessary for optimizing bisphenols extraction procedure from solid parts of food. On the other hand, considering all the above benefits, the authors hope that this study would be beneficial for the further development and application of microgel sorbents. Conceptualization, investigation, validation and writing--original draft preparation, A.K. ; formal analysis and synthesis, M.M. ; writing--review and editing, M.K. and M.B. ; supervision, M.B. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Science Centre, Poland, under grant number 2018/31/B/ST5/02859. Not applicable. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.