## 3 Results and Discussion
### Application to Real Samples  
In order to demonstrate the applicability of the proposed QuEChERS- LC-LTQ/Orbitrap MS methodology, twenty-seven (27) representative dairy commodity samples were analyzed (see Section 2.2). The results are summarized in Table 2.  
The mean concentration values of the EDCs determined were calculated from the samples where analytes were detected at concentrations above the method quantification limits (>LOQs). Generally, 96.3% of the samples analyzed contained the target analytes while in only 3.7% of them no residues were found, which is mainly attributed to the positive detections of octylphenol. A characteristic Extracted Ion (EI) Chromatogram of a yogurt sample found to contain both BPA and OP residues after being subjected to QuEChERS extraction followed by LC-LTQ/Orbitrap MS analysis is shown in Figure 4. The Data Dependent Orbitrap FT spectrum that confirms the identity of BPA and OP residues detected is illustrated. Low mass deviation (<2.14 ppm) was observed for both parent and fragment ions. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{3}{*}{**EDCs**} & **Average** & **Concentration** & **Positive** & \\  & **Concentration a**  & **Range** & **Detections b**  & **n.d.\%** \\  & **(\(\mu\)g kg\({}^{-1}\)) (\(\pm\)SD)** & **(\(\mu\)g kg\({}^{-1}\))** & **(\(\mu\)) c**  & **n.d.\%** \\ \hline BPA & 9.4 (\(\pm\)4.2) & 9.1–10.4 & 7 (0) & 74.1 \\ OP & 174.1 (\(\pm\)128.0) & 0.5–301.4 & 26 (1) & 3.7 \\ NP & 137.7 (\(\pm\)93.0) & 36.7–398.8 & 8 (0) & 70.4 \\
4 NP & 296.7 (\(\pm\)130.3) & 66.1–428.7 & 5 (3) & 70.4 \\ \hline \end{tabular}
\end{table} 
Table 2: Detected target EDCs residues in 27 samples of dairy products. The detailed results from the dairy commodities' analysis are depicted in Figure S10. According to the results, 4-t-OP has been the most frequently detected compound. It is followed by the NP isomers and lastly BPA, for which the lower detection frequency rate was observed (31.0%). Overall results (patterns and levels) were within the range reported in previous publications for the corresponding matrices [9; 34; 35; 36; 37; 38], which indicate the undoubting presence of these compounds in dairy commodities, even when infant formulas are concerned. However, no Maximum Residue Limits (MRLs) have been established for these industrial chemicals. Nevertheless, along with the need for further toxicity studies and food monitoring, the European Food Safety Authority (EFSA) completed its first full risk assessment of BPA in 2006 [40], which established a Tolerable Daily Intake (TDI) of 50 ng g-1 (body weight), with exposure below this level. Since then, EFSA has reviewed new scientific information on BPA several times. Based on EFSA opinion of 2015 [15], the TDI--however, temporary (t)--was lowered to 4 ng g-1 of bw/day. Furthermore, BPA dietary intake can be calculated based on the recommended t-TDI using the following formula:  
\[\text{Daily intake}=\frac{C*dIR}{BW} \tag{2}\]  
where C is the average or maximum BPA concentration (\(\mu\)g kg-1) found across the analyzed milk samples; \(dIR\) is the daily ingestion rate (daily consumption of milk in Greece) and BW is the corresponding average Body Weight of consumers. Similarly to other studies [41; 42], the dIR used in the above equation is the average daily consumption of milk in Greece for adults, estimated to be 264.9 g /day according to the National Dietary Guidance for adults [43]. Bw is the corresponding average body weight of 60 kg for Greek consumers. Detected concentration levels (MDL-10.4 ng g-1) for BPA in milk samples resulted in 0.36% of TDI for the medium case (average BPA concentrations) and 1.15% of TDI for the worst case (maximum BPA concentration). Figure 4: LC-LTQ/Orbitrap MS Extracted Ion Chromatogram (EIC) of a strained yogurt sample where BPA and OP were detected at the concentration of 9.1 and 215.4 ng g-1, respectively: (**a**) BPA; (**b**) OP; (**c**) nonylphenol isomers (NP, 4 NP) were not detected.