## 3 Results and Discussion  
### Optimization of Experimental Conditions  
The GC-ECD chromatogram using solid-phase micro-extraction (SPME) for the 20 organochlorine pesticides standard is given in Figure 2. All chlorinated pesticides were eluted in 28 min and were well resolved under the selected GC operating conditions as mentioned in Section 2.6. The extraction of pesticides from water was carried out in 20 mL glass vials by dipping the SPME fiber in the solution using a COMBI PAL CTC autosampler. For maximum efficiency in the SPME procedure, several variables, such as the fiber extraction and desorption steps, needed to be optimized. The various parameters  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Pesticide**} & \multicolumn{2}{c}{**SFf(mg kg\({}^{-1}\)**} & \multicolumn{2}{c}{**R\({}_{\text{f}}\)D/(mg kg\({}^{-1}\)**} & \multicolumn{2}{c}{**Cancer Risk (10\({}^{-6}\))**} & \multicolumn{2}{c}{**Hazard Quotient (10\({}^{-2}\))**} \\  & **per Day\({}^{-1}\)\({}^{*}\)** & **per Day\({}^{*}\)** & **(for Children)** & **(for Adults)** & **(for Children)** & **(for Adults)** \\ \hline \(\alpha\)-BHC & 6.3 & \(5.0\times 10^{-4}\) & 0 & 0 & 0 & 0 \\ \(\beta\)-BHC & 1.8 & \(2.0\times 10^{-4}\) & 0 & 0 & 0 & 0 \\ \(\gamma\)-BHC & 1.3 & \(3.0\times 10^{-4}\) & 0–2.05 & 0.96 & 0.52 & 0.24 \\ \(\delta\)-BHC & / & / & 0 & 0 & & \\ Heptachlor & 4.5 & \(5.0\times 10^{-4}\) & 0–33.29 & 15.53 & 1.48 & 0.69 \\ Aldrin & 17 & \(3.0\times 10^{-5}\) & 0–16.30 & 7.61 & 3.20 & 1.49 \\ Heptachlor & 9.1 & \(1.3\times 10^{-5}\) & 0 & 0 & 0 & 0 \\ poxide & \(\gamma\)-Chlorane & / & / & 0 & 0 & 0 & 0 \\ \(\alpha\)-Chlorane & / & / & 0 & 0 & 0 & 0 \\ Endosulfan I & / & / & 0 & 0 & 0 & 0 \\
4,4\({}^{\prime}\)-DDE & 0.34 & / & 0.47 & 0.22 & - & - \\ Dieldrin & 16 & \(5.0\times 10^{-5}\) & 14.25 & 6.65 & 1.78 & 0.83 \\ Endrin & / & \(3.0\times 10^{-4}\) & 0 & 0 & 0 & 0 \\ Endosulfan II & / & / & 0 & 0 & 0 & 0 \\
4,4\({}^{\prime}\)-DDD & 0.24 & \(2.0\times 10^{-3}\) & 0 & 0 & 0 & 0 \\ Endrin & / & \(3.0\times 10^{-4}\) & - & - & 0.68 & 0.32 \\ Endrin ketone & / & / & 0 & 0 & 0 & 0 \\
4,4\({}^{\prime}\)-DDT & 0.34 & \(5.0\times 10^{-4}\) & 0 & 0 & 0 & 0 \\ Endosulfan & / & / & 0 & 0 & 0 & 0 \\ sulfide & / & / & 0 & 0 & 0 & 0 \\ Methoxychlor & / & / & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular} \({}^{*}\) Toxicological parameters for some organochlorine pesticides. /: no given parameter value.  
\end{table}
Table 1: Health risks due to organochlorine pesticides for adults and children in the Charsadda district through surface water.  
studied here were the fiber extraction and desorption time, solution pH, agitation of samples, stirring speed and splitless time. The pH was adjusted with 0.1M HCl and 0.1M NaOH by measurement with a digital pH meter ([PERSON], pH/ISE Meter pH-250L, Korea). After the extraction of pesticides by the SPME fiber, the pesticides were injected to the column through thermal desorption in the injector of the GC. To achieve good results, all investigations were performed in triplicate and average values were obtained.  
The parameters selected for SPME fiber were: a fiber extraction time of 45 min, desorption time of 2 min, agitator speed of 250 rpm, and pH of 6.2. These selected parameters were used to develop the analytical procedure and for the chlorinated pesticides analysis in real water samples.