## 3 Results  
### Validation Results  
The results of the automated pipetted calibration are shown in Figure 4. The calibration curves are linear and show coefficients of determination of R\({}^{2}\) > 0.999. In addition, chromatograms and spectra for the analytes under the respective calibration curve are shown as examples in Figure 4. Samples are stable for the 24 h period required for sample preparation and analysis. Peak area size is not undergoing significant changes in accordance with the manufacturer's specifications. According to [PERSON] and [PERSON] et al., the material of the container, plastic and polypropylene or glass is more crucial for the recovery of the analytes, as they are lipophilic and adhere to the walls of polypropylene and plastic containers [69,70]. The results of the validation are shown in Tables 1-3. The recoveries for \(\Delta\)9-THC-D\({}_{3}\), THC-OH and THC-COOH from serum range from 94.28% to 104.15% with coefficients of variation between 0.44% and 3.11%. The methodological limits of detection and quantification are 0.156 ng/mL and 0.176 ng/mL for \(\Delta\)9-THC-D\({}_{3}\) from serum, 0.349 ng/mL and 0.384 ng/mL for THC-OH and 0.896 ng/mL and 0.987 ng/mL for THC-COOH, respectively, and are thus higher than the analytical limits of detection and quantification because dilution occurs during sample preparation and is not compensated during SPE. The coefficient of variation of the measurement precision is less than 0.53%. Figure 4: Calibration curves with calibration curve equation y and coefficient of determination R\({}^{2}\), chromatograms and mass spectra for (**a**) \(\Delta\)9-THC-D\({}_{3}\) (**b**) THC-OH (**c**) THC-COOH. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Searum**} & \multicolumn{6}{c}{**A9-THC-D3**} & \multicolumn{6}{c}{**THC-OH**} & \multicolumn{6}{c}{**THC-COOH**} \\ \cline{2-13}  & & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} \\ \hline  & \multicolumn{6}{c}{**No. of**} & \multicolumn{6}{c}{**Mean**} & \multicolumn{6}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} \\  & **Samples** & **Value** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** \\ \hline Recovery & 25 & 101.21 & 0.86 & 100.12 & - & 104.15 & 99.54 & 1.51 & 96.41 & - & 101.45 & 100.65 & 0.52 & 99.69 & - & 101.75 \\ \hline Within- & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} & \multicolumn{6}{c}{**Range**} \\ \hline  & \multicolumn{6}{c}{**Mean**} & \multicolumn{6}{c}{**Mean**} & \multicolumn{6}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} & \multicolumn{1}{c}{**Mean**} & \multicolumn{1}{c}{**CV**} & \multicolumn{1}{c}{**Min**} & \multicolumn{1}{c}{**-**} & \multicolumn{1}{c}{**Max**} \\  & **Samples** & **Value** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** & **[\%]** \\ \hline Recovery & 25 & 101.21 & 0.86 & 100.12 & - & 104.15 & 9 The recoveries for \(\Delta\)9-THC-D\({}_{3}\), THC-OH and THC-COOH from urine range from 77.54% to 99.64% with coefficients of variation between 1.03% and 3.89%.