## 3 Results and Discussion
### Method Validations
#### 3.3.2 Recovery Rates
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Soil**} \\ \cline{3-6}
**No.** & **Pesticides** & \multicolumn{2}{c}{**Low (10 \(\upmu\) kg\({}^{-1}\))**} & \multicolumn{2}{c}{**High (50 \(\upmu\) kg\({}^{-1}\))**} \\ \cline{3-6}  & & **Rec.** & **RSD** & **Rec.** & **RSD** \\ \hline
1 & Abamectin B1 & 82.5 & 4.4 & 82.3 & 4.3 \\
2 & Acephate & 103.6 & 4.9 & 101.6 & 9.5 \\
3 & Acetamiprid & 82.3 & 4.6 & 99.9 & 1.3 \\
4 & Aldicarb & 96.7 & 3.2 & 101.3 & 2.3 \\
5 & Amisulbrom & 91.8 & 8.5 & 93.8 & 4.4 \\
6 & Azimsulfuron & 76.5 & 2.3 & 91.8 & 5.0 \\
7 & Azimphos-methyl & 79.0 & 8.1 & 89.1 & 6.6 \\
8 & Azoxystrobin & 96.1 & 4.0 & 114.2 & 2.2 \\
9 & Bendicocarb & 80.9 & 1.5 & 86.1 & 2.1 \\
10 & Bensulfuron-methyl & 78.2 & 4.8 & 84.0 & 2.0 \\
11 & Benthiavalicarb & 83.9 & 6.2 & 88.7 & 0.6 \\
12 & Benzobicycloon & 86.1 & 4.7 & 91.9 & 2.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Recoveries of 40 pesticides in the untreated soil using LC-MS/MS (\(n=3\)). Recoveries for the other 179 pesticides are listed in Table S6. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{4}{c}{**Soil**} \\ \cline{3-6}
**No.** & **Pesticides** & \multicolumn{2}{c}{**Low (10 \(\upmu\) kg\({}^{-1}\))**} & \multicolumn{2}{c}{**High (50 \(\upmu\) kg\({}^{-1}\))**} \\ \cline{3-6}  & & **Rec.** & **RSD** & **Rec.** & **RSD** \\ \hline
19 & Chlorantraniliprole & 100.41 & 16.0 & 97.45 & 3.9 \\
20 & Chlordane-cis & 112.76 & 7.1 & 96.46 & 3.4 \\
21 & Chlordane-trans & 102.47 & 10.7 & 96.54 & 3.3 \\
22 & Chlorfenapyr & 98.35 & 9.6 & 101.48 & 2.1 \\
23 & Chlorfenapyr & 107.00 & 1.8 & 97.45 & 0.9 \\
24 & Chlorfluazuron & 96.71 & 11.8 & 98.19 & 2.3 \\
25 & Chlorobenzalate & 106.17 & 2.0 & 95.97 & 1.3 \\
26 & Chlorpropham & 98.77 & 6.6 & 96.71 & 3.9 \\
27 & Chlorpyrifos-methyl & 97.53 & 5.8 & 98.77 & 4.3 \\
28 & Cyluthrin & 110.29 & 2.8 & 96.13 & 1.6 \\
29 & Cyläothrin & 112.76 & 1.7 & 92.68 & 0.6 \\
30 & Cypermethrin & 106.58 & 1.8 & 93.91 & 2.4 \\
31 & Cyprodini & 101.24 & 5.6 & 93.66 & 3.2 \\
32 & DDD-p,p\({}^{\prime}\) & 116.05 & 1.1 & 105.76 & 1.2 \\
33 & DDE-p,p\({}^{\prime}\) & 101.65 & 4.9 & 98.68 & 2.9 \\
34 & DDT-o,p\({}^{\prime}\) & 113.17 & 2.7 & 103.13 & 1.1 \\
35 & DDT-p,p\({}^{\prime}\) & 106.17 & 3.1 & 94.90 & 1.0 \\
36 & Deltamethrin (Tralomethrin deg.) & 109.47 & 1.3 & 90.78 & 4.1 \\
37 & Diclofop-methyl & 102.47 & 1.2 & 95.72 & 2.3 \\
38 & Dicloran & 112.35 & 4.0 & 93.75 & 8.2 \\
39 & Dicofol & 114.82 & 2.8 & 99.18 & 1.6 \\
40 & Dieldrin & 99.59 & 10.5 & 96.30 & 8.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._MeCN was selected to use as the extraction solvent for residual pesticides in soil samples, as other studies used MeCN for soil extraction [22; 23]. In our study, MeCN was properly used to extract multiresidue pesticides from soil samples. In addition, to obtain better efficiency in extraction and recoveries of multiresidue pesticides from soil samples, the QuEChERS procedure was employed in our study, as all recovery rates were in the range considered effective and promising. As a pressurized liquid extraction failed to obtain a satisfactory recovery rate within the range of 65.1% to 122.2% for 25 pesticides in the soil samples, the QuEChERS procedure provided better recoveries, with the extraction recovery in the range of 79.4 to 113.3% with RSDs of 1.0 to 12.2% [24]. On the other hand, the QuEChERS procedure may have caused strong salting-out effects, as the mean recoveries of paclobutrazol (125%) and fenvalerate (122%) treated at the level of 5 u kg\({}^{-1}\) were observed to be higher than for other pesticides [25]. However, such salting-out effects were not observed in our study. Therefore, the recoveries of multiresidue pesticides were generally between 70 and 120% with RSDs below 20%, indicating that the proposed method in this study was feasible to analyze 340 pesticides in soil samples.