## 3 Results and Discussion
### Method Application  
The method was validated by analyzing 31 commercial milk samples purchased randomly from the supermarket. The results revealed that only THIA and CLO were detected in milk samples. Among the 31 samples, one sample contained THIA (3.4 \(\upmu\)g/kg), and one sample contained CLO (80 \(\upmu\)g/kg). To the best of our knowledge, this is the first study conducted on NEO levels for a set of the milk samples in Taiwan. The results indicated that NEO residue levels present in milk are safe for human consumption. [PERSON] et al. assessed NEO residues in 128 food samples collected from four parts of Taiwan and reported the highest detection rate for ACE among NEO residues (59%), with the highest level of 80.5 \(\upmu\)g/kg [5]. Moreover, at these concentrations, NEO residues in the diet of preschool children in Taiwan did not exceed the hazard index of 1.  
Few studies have reported NEOs through milk analysis despite the importance of milk as a food. [PERSON] et al., reported an ionic-based ultrasound-assisted dual magnetic nanocellulose microextraction method followed by HPLC-DAD-MS in milk samples [18]. The LOQ range of the six NEOs was 20-60 \(\upmu\)g/kg. [PERSON] et al. developed an SPE technique with Chem Elut cartridges followed by HPLC-DAD for determination of the levels of four NEOs in bovine milk [14]. The LOQ range of the four NEOs was 10-40 \(\upmu\)g/kg. [PERSON] et al. reported a similar pretreatment method that used Chem Elut SPE cartridges, but analysis was conducted through HPLC-MS/MS [13]. The LOQ of five NEOs was 1 \(\upmu\)g/kg in sheep and cow milk samples. [PERSON] et al. reported SPE with HLB cartridges followed by UPLC-MS/MS, and the LOQ range of the seven NEOs was 0.37-2.0 \(\upmu\)g/kg in milk samples [10]. [PERSON] et al. and [PERSON] et al. developed SPE with C18 cartridges followed by UHPLC-MS/MS for analysis of the levels of five and four NEOs in milk samples [15; 16]. The LODs of the NEOs ranged from 0.01 and 0.05 \(\upmu\)g/kg. [PERSON] et al. reported a QuEChERS method followed by HPLC-MS/MS, and the LOQ range of the four NEOs was 1.0-2.0 \(\upmu\)g/kg in human milk [19]. [PERSON] and [PERSON] proposed a very sensitive UHPLC-MS/MS method with an LOQ of \(\leq\)10 ng/L for determination of the levels of five NEOs in milk [17]. Compared with the aforementioned techniques, this study established a simple, fast, efficient and low cost liquid-liquid extraction-UHPLC-MS/MS method with satisfactory results for MRL in milk. The method developed shows satisfactory validation parameters in linearity, low LOD, accuracy and precision and fits for the simultaneous determination of seven NEOs in milk samples.  
The presence of NEOs in breast milk has received increasing interest since human milk is the main nutrition for infants and reveals neonatal exposure. As our knowledge, limited data are available on the NEO residues in breast-milk [17; 19]. Exposure of the neonates to NEOs appears to be important, because NEOs are neurotoxicants and may cause neurotoxicity caused by ACE and IMI [8; 22]. Future studies are needed to monitor milk levels in breastfeeding women and to study potential risk for NEOs of newborns through milk consumption.