## 3 Results
### Real Sample Analysis  
The proposed MSPE method was applied to determination of OCPs in real agricultural irrigation water samples, including tap water, river water, and underground water. The results are summarized in Table 4 and the total ion chromatograms (TICs) of the analytes acquired from the tap water samples are shown in Figure 7. There are no OCPs in the selected water samples and the recovery results indicate that the developed method has good utility for analysis of OCPs in real water samples.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{3}{*}{**Matrix**} & \multirow{3}{*}{**Analyte**} & \multicolumn{4}{c}{**Spiked Concentration (\(\mu\)g L\({}^{-1}\), \(n=3\))**} \\ \cline{3-6}  & & **0** & **10** & **100** \\ \cline{3-6}  & & **Found** & **Recovery (\%)** & **RSD (\%)** & **Recovery (\%)** & **RSD (\%)** \\ \hline \multirow{7}{*}{Tap water} & \(\alpha\)-HCH & \(<\)LOD & 83.4 & 7.4 & 84.7 & 0.7 \\  & \(\beta\)-HCH & \(<\)LOD & 92.5 & 9.6 & 103.7 & 0.6 \\  & \(\gamma\)-HCH & \(<\)LOD & 93.3 & 5.5 & 91.9 & 0.4 \\  & \(\delta\)-HCH & \(<\)LOD & 94.6 & 6.6 & 111.1 & 1.0 \\  & \(\alpha\),p\({}^{\prime}\)-DDE & \(<\)LOD & 85.4 & 3.4 & 99.6 & 5.3 \\  & p,p\({}^{\prime}\)-DDE & \(<\)LOD & 78.1 & 1.5 & 107.5 & 3.1 \\  & p,p\({}^{\prime}\)-DDD & \(<\)LOD & 76.0 & 2.5 & 97.0 & 2.5 \\  & \(\alpha\),p\({}^{\prime}\)-DT & \(<\)LOD & 83.1 & 5.4 & 89.2 & 2.1 \\  & p,p\({}^{\prime}\)-DT & \(<\)LOD & 93.7 & 2.1 & 105.7 & 1.6 \\ \hline \multirow{7}{*}{River water} & \(\alpha\)-HCH & \(<\)LOD & 76.8 & 5.7 & 80.5 & 2.4 \\  & \(\beta\)-HCH & \(<\)LOD & 91.3 & 3.1 & 102.5 & 0.8 \\  & \(\gamma\)-HCH & \(<\)LOD & 84.1 & 8.5 & 91.2 & 3.5 \\  & \(\delta\)-HCH & \(<\)LOD & 74.9 & 5.9 & 112.7 & 2.6 \\  & \(\alpha\),p\({}^{\prime}\)-DDE & \(<\)LOD & 110.8 & 4.7 & 94.3 & 0.1 \\  & p,p\({}^{\prime}\)-DDE & \(<\)LOD & 102.5 & 4.8 & 100.9 & 1.2 \\  & p,p\({}^{\prime}\)-DDD & \(<\)LOD & 101.9 & 3.4 & 92.2 & 0.7 \\  & \(\alpha\),p\({}^{\prime}\)-DT & \(<\)LOD & 108.6 & 4.3 & 86.9 & 1.2 \\  & p,p\({}^{\prime}\)-DT & \(<\)LOD & 110.8 & 3.5 & 100.9 & 0.8 \\ \hline \multirow{7}{*}{Underground water} & \(\alpha\)-HCH & \(<\)LOD & 81.0 & 8.7 & 80.3 & 3.3 \\  & \(\beta\)-HCH & \(<\)LOD & 83.9 & 7.8 & 97.2 & 2.1 \\ \cline{1-1}  & \(\gamma\)-HCH & \(<\)LOD & 90.1 & 7.5 & 80.4 & 5.2 \\ \cline{1-1}  & \(\delta\)-HCH & \(<\)LOD & 79.5 & 15.3 & 112.7 & 2.0 \\ \cline{1-1}  & \(\alpha\),p\({}^{\prime}\)-DDE & \(<\)LOD & 101.5 & 8.4 & 82.9 & 1.9 \\ \cline{1-1}  & p,p\({}^{\prime}\)-DDE & \(<\)LOD & 95.3 & 7.6 & 81.0 & 1.4 \\ \cline{1-1}  & \(\alpha\),p\({}^{\prime}\)-DDD & \(<\)LOD & 92.8 & 8.9 & 75.1 & 2.2 \\ \cline{1-1}  & \(\alpha\),p\({}^{\prime}\)-DT & \(<\)LOD & 111.1 & 6.4 & 110.3 & 3.2 \\ \cline{1-1}  & p,p\({}^{\prime}\)-DT & \(<\)LOD & 116.3 & 3.7 & 90.5 & 2.3 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Analytical results for determination of organochlorine pesticides in real water samples.  
Figure 7: Total ion chromatograms of the nine organochlorine pesticides in water samples obtained by gas chromatography–tandem triple quadrupole mass spectrometry: (**a**) tap water; (**b**) river water; (**c**) underground water; (**d**) tap water spiked at 10 \(\mu\)g L\({}^{-1}\); and (**e**) tap water spiked at 100 \(\mu\)g L\({}^{-1}\).