## 2 Results and Discussion
### Validation of the Proposed Methodology

Table 2: LODs, LLOQs, calibration equations and \(r^{2}\) achieved for the six TCAs through BA\(\mu\)E(C18)-\(\mu\)LD/LVI-GC-MS(SIM) methodology, under optimized experimental conditions. Matrix effects, average recovery yields and process efficiency were also performed at two different concentration levels (25 and 750 \(\upmu\)g L\({}^{-1}\)), as presented in Table 4. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**TCAs**} & \multirow{2}{*}{
\begin{tabular}{c} **Spiking Level** \\ **(\(\upmu\)g L\({}^{-1}\))** \\ \end{tabular} } & \multicolumn{2}{c}{**Matrix Effects**} & \multicolumn{2}{c}{**Recovery Yields**} & \multicolumn{2}{c}{**Process Efficiency**} \\  & & **(\%) \(\pm\) RSD (\%)** & \multicolumn{2}{c}{**(\%) \(\pm\) RSD (\%)**} & \multicolumn{2}{c}{**(\%) \(\pm\) RSD (\%)**} & \multicolumn{2}{c}{**(\%) \(\pm\) RSD (\%)**} \\ \hline \multirow{3}{*}{**AMT**} & 25.0 & 90.2 & \(\pm\) & 6.6 & 95.3 & \(\pm\) & 9.6 & 86.0 & \(\pm\) & 7.5 \\ \cline{2-9}  & 750.0 & 93.7 & \(\pm\) & 12.5 & 107.9 & \(\pm\) & 6.9 & 101.1 & \(\pm\) & 12.9 \\ \hline \multirow{3}{*}{**MIA**} & 25.0 & 100.1 & \(\pm\) & 9.8 & 95.3 & \(\pm\) & 7.2 & 95.4 & \(\pm\) & 8.6 \\ \cline{2-9}  & 750.0 & 111.5 & \(\pm\) & 11.2 & 111.5 & \(\pm\) & 7.7 & 124.3 & \(\pm\) & 11.7 \\ \hline \multirow{3}{*}{**TRI**} & 25.0 & 102.1 & \(\pm\) & 8.4 & 103.3 & \(\pm\) & 9.3 & 105.5 & \(\pm\) & 12.0 \\ \cline{2-9}  & 750.0 & 99.3 & \(\pm\) & 8.2 & 109.0 & \(\pm\) & 5.0 & 108.2 & \(\pm\) & 7.9 \\ \hline \multirow{3}{*}{**IMP**} & 25.0 & 91.9 & \(\pm\) & 4.1 & 92.3 & \(\pm\) & 11.1 & 84.9 & \(\pm\) & 10.4 \\ \cline{2-9}  & 750.0 & 109.3 & \(\pm\) & 13.9 & 106.5 & \(\pm\) & 10.0 & 116.5 & \(\pm\) & 12.6 \\ \hline \multirow{3}{*}{**MIR**} & 25.0 & 95.6 & \(\pm\) & 10.9 & 108.5 & \(\pm\) & 12.3 & 103.6 & \(\pm\) & 12.0 \\ \cline{2-9}  & 750.0 & 112.9 & \(\pm\) & 14.4 & 99.0 & \(\pm\) & 9.9 & 111.7 & \(\pm\) & 13.9 \\ \hline \multirow{3}{*}{**DOT**} & 25.0 & 91.3 & \(\pm\) & 4.4 & 99.6 & \(\pm\) & 8.9 & 90.9 & \(\pm\) & 8.4 \\ \cline{2-9}  & 750.0 & 99.4 & \(\pm\) & 11.6 & 103.7 & \(\pm\) & 7.5 & 103.1 & \(\pm\) & 13.9 \\ \hline \end{tabular}
\end{table} 
Table 4: Matrix effects, recovery yields and process efficiency obtained for the six TCAs at two different concentrations by BA\(\upmu\)E(C18)-\(\upmu\)LD/LVI-GC-MS(SIM) methodology, under optimized experimental conditions. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**TCAs**} & \multirow{2}{*}{ \begin{tabular}{c} **Spiking Level** \\ **(\(\upmu\)g L\({}^{-1}\))** \\ \end{tabular}  } & \multicolumn{4}{c}{**Intraday**} & \multicolumn{2}{c}{**Interday**} \\ \cline{3-8}  & & **Accuracy (\%) \(\pm\) Precision (\%)** & **Accuracy (\%) \(\pm\) Precision (\%)** \\ \hline \multirow{3}{*}{**AMT**} & 10.0 & 5.1 & \(\pm\) & 8.2 & 20.0 & \(\pm\) & 15.0 \\  & 50.0 & \(-\)5.5 & \(\pm\) & 4.6 & \(-\)5.0 & \(\pm\) & 8.9 \\  & 500.0 & 1.7 & \(\pm\) & 4.8 & 2.9 & \(\pm\) & 12.2 \\  & 1000.0 & 4.8 & \(\pm\) & 8.8 & \(-\)4.4 &Matrix effects were found to be in between 90.2 and 112.9% (RSD < 14.4%). Results above 100% show ionic enrichment and below, ionic suppression; 100% is the ideal, although it is impossible to eliminate matrix effects [49; 50; 51]. The average recovery yields achieved were between 92.3 and 111.5% (RSD < 12.4%). Finally, the process efficiency ranged from 84.9 to 124.3% (RSD < 13.9%). These data proved that the developed methodology is well suited to determine trace levels of TCAs in urine matrices.