## 4 Conclusions  
QuEChERS-based extraction methodology combined with LC-LTQ/Orbitrap MS has been optimized by chemometric approaches, with the significant factors determined using a P-B screening design and subsequently optimized using CCD combined with DF, for the determination of the selected EDCs, BPA, OP and NP isomers in dairy matrices. The methodology was validated fulfilling the requirements of performance characteristics. The successful application of the developed method to dairy samples confirmed its reliability and efficacy as a method of choice for routine analysis of a wide variety of dairy products for the selected EDCs residues. Detected concentration levels are not related to the fat  
Figure 5: Illustration of the percent (%) occurrence of the detected EDCs in relation to the percent (%) fat content of the analyzed food commodities. content of foodstuffs while no clear trends can be concluded in relation to the packing material. Finally, for BPA the detected concentration levels in milk samples resulted in less than 1.15% of the tolerable daily intake. The following are available online at [[https://www.mdpi.com/article/10.3390/app11209358/s1](https://www.mdpi.com/article/10.3390/app11209358/s1)]([https://www.mdpi.com/article/10.3390/app11209358/s1](https://www.mdpi.com/article/10.3390/app11209358/s1)), Table S1: Characteristics of the selected dairy products; Table S2: Data from LC-Orbitrap/MS2 analysis of the target EDCs; Table S3: LC-Orbitrap MS parameters under investigation using a fractional factorial design 3(4-1) and their coded values; Table S4: Plackett-Burman design with the selected factors and their coded values; Table S5: ANOVA table generated from the Plackett-Burman design; Table S6: The Central Composite Design (CCD) including the selected factors after screening design and the mean recovery (%) used as optimal response; Table S7: ANOVA table generated from the Central Composite Design (CCD); Table S8: Mean recoveries obtained from the optimized QuEChERS extraction of the target EDCs from yogurt samples at 10 and 50 ng g\({}^{-1}\) fortification levels; Figure S1: LC-LTQ/Orbitrap MS extracted in (El) chromatogram of a standard solution of the selected compounds at a concentration level of 100 ug L\({}^{-1}\). Peaks are assigned as follows: (1) BPA, (2) OP, (3) NP (t), (4) 4 NP; Figure S2: Normal probability plot of the studentized residuals (normality test curve for the fractional factorial design 3(4-1)); Figure S3: Profile of the predicted values and desirability function of the analytes response (S/N). Optimum values are designated by dotted lines; Figure S4: Response surface plots for the fractional factorial design 3(4-1); Figure S5: Standardized main effect Pareto chart for the Plackett-Burman design of the screening experiment. Vertical line in the chart defines 95% confidence level; Figure S6. Normal probability plot of the studentized residuals (normality test curve for the central composite design 23); Figure S7: Pareto chart for the Central Composite Design (CCD). Vertical line in the chart defines 95% confidence level; Figure S8: Profile of the predicted values and desirability function of the analytes' response (mean recovery %) after CCD employment. The optimal values are designated by dotted lines; Figure S9: Matrix effect of the EDCs under study, calculated from the slopes of the calibration curves; Figure S10: (a) Concentration levels of EDCs residues; (b) percentage concentration patterns in all dairy commodities analyzed by QuEChERS coupled to LC-Orbitrap MS. Numbers of the commodities are assigned according to Table S1; Figure S11: Mean concentrations (ug kg\({}^{-1}\)) of the detected EDCs in relation to the type of the packaging material of the analyzed dairy commodities. Conceptualization, V.B. and T.A. ; data curation, V.B. and V.K. ; formal analysis, V.B., V.K. and I.K. ; funding acquisition, T.A. and I.K. ; investigation, V.B. and V.K. ; methodology, V.B., V.K. and I.K. ; resources, T.A. ; software, V.B. and V.K. ; supervision, T.A. ; validation, V.B. and V.K.