## 4 Discussion  
In the present study, 14 residual veterinary drugs, namely three chloramphenicol classes (chloramphenicol, florfenicol, and thiamphenicol), five quinolone classes (danofloxacin, difloxacin, enrofloxacin, flumequine, and sarafloxacin), MG, LMG, and four nitrofuran metabolites (AMOZ, AOZ, AH, and SC), were analyzed in 52 shrimp samples collected from aquaculture areas in Taiwan. To validate the presence of these compounds in samples, we evaluated the mean recovery (as a measure of trueness), linearity, sensitivity, and repeatability (as a measure of precision) according to EU guidelines (SANCO/12495/2011) [10]. Because chloramphenicol, nitrofuran metabolites, MG, and LMG are banned from use in edible animals and danofloxacin, difloxacin, enrofloxacin, flumequine, and sarafloxacin are banned from use in decapods, the TFDA does not recommend MRLs in shrimp. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Shrimp**} & **Surveyed** & **Violated Targets** & **Detected** & **Average 1** & **Violated** \\  & **Samples** & **(No.)** & **Residues (ng/g)** & **(ng/g, Residues)** & **Ration 2 (\%)** \\ \hline \multirow{2}{*}{Whiteleg shrimp} & \multirow{2}{*}{23} & enrofloxacin (1) & 5.62 & 0.24 (enrofloxacin) & 3.77 (2/53) \\  & & flumequine (1) & 1.52 & 0.07 (flumequine) & \\ \multirow{2}{*}{Grass shrimp} & \multirow{2}{*}{16} & chloramphenicol (1) & 0.31 & 0.02 (chloramphenicol) & 1.89 (1/53) \\  & & flumequine (1) & 1.01 & 0.07 (flumequine) & 1.89 (1/53) \\ \hline \multirow{2}{*}{Total} & \multirow{2}{*}{53} & chloramphenicol (1) & 0.31 & 0.01 & \\  & & enrofloxacin (1) & 5.62 & 0.11 & 7.55 (4/53) \\ \multirow{2}{*}{} & \multirow{2}{*}{53} & Flumequine (2) & 1.01–1.52 & 0.05 & \\ \hline \hline \end{tabular}  
* Estimated from all samples, including samples with detected and undetected concentrations.
* Samples with residual concentrations lower than the LOQ were considered to have undetectable concentrations.  
\end{table} 
Table 1: Detection levels of banned veterinary drugs in various shrimp samples collected between July 2016 and December 2017. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**OCPs**} & \multicolumn{2}{c}{**EDI**} & \multirow{2}{*}{**EDI\% of ADI**} & \multirow{2}{*}{**ADI (FAO/WHO)**} \\  & **(ng/kg Body Weight/Day)** & & & **(mg/kg Body Weight/Day)** \\ \cline{2-4} \cline{6-5}  & **Male** & **Female** & **Male** & **Female** \\ \hline Enrofloxacin & 0.18 & 0.14 & 0.01 & 0.01 & 0.002 \\ Flumequine & 0.08 & 0.06 & 0.0003 & 0.002 & 0.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Estimated dietary intake of quinolone residues in Taiwanese adults. Therefore, the residues of these banned compounds in shrimp were detected and sufficiently indicated the degree of legal compliance regarding the use of these products. The Commission Decision 2002/657/EC criteria for evaluation of veterinary drug residues in animals and animal products are stipulated on the basis of mass spectrometry at numerous identification points (IPs) [16]. Source conditions were optimized to obtain 1.5 IP from product ions and one IP from precursor ions for each compound. In general, obtaining four IPs at the lowest level is required for analyzing banned compounds. In the present study, veterinary drugs were analyzed in the MRM mode by monitoring three different ions (one precursor and two fragment ions). Using this approach, we achieved four IPs (one IP from a single precursor ion and three IPs from two fragment ions), as mandated by the aforementioned guidelines. Our analysis method successfully identified the residues of MG, LMG, chloramphenicol classes, quinolone classes, and nitrofuran metabolites. The analytical extraction method for aquatic samples was designed by [PERSON] et al. [8]. In this method, ACN and hexane are used to extract samples for simultaneously screening multiple classes of drug residues, including macrolides, \(\beta\)-lactam antibiotics, dyes, quinolones, tetracyclines, and antimycotic imidazoles.