## 2 Results and Discussion  
### Methodology Performance  
A methodology that was previously optimized and validated by our group for infusions of chamomile, leemon verbena, lemon balm, green tea, and peppermint was used as a starting point [30]. Parameters, such as linearity, limits of detection and quantification, the matrix effect (ME), selectivity, and recovery, were re-evaluated to determine the performance of the method in the selected samples. The samples were divided into two groups: tea and herbal infusions. Tea-B-3 and Her-Inf-4 (Table S1) were selected, and matrix-matched calibration curves were created. To achieve this, cold infusions were filtered and doped at increasing concentrations before the \(\upmu\)SPEed(r) procedure. Seven levels were evaluated in a linear range of 0.1-25 ng/mL in the liquid infusion samples. This linear range corresponds to 1.25-313 ng/mL following the methodology, due to the high pre-concentration capacity of the method used (12.5-fold). Linearity was evaluated with the correlation coefficient (R\({}^{2}\)) of each matrix-matched calibration curve, obtained by plotting the peak area of each analyte versus the concentration of each point. The matrix-matched calibration curves for the Tea-B-3 and the Her-Inf-4 infusion samples are listed in Table 1. The results showed good linearity, with R\({}^{2}\) between 0.995 and 0.998 for both analytes. In addition, the method detection limit (MDL) and method quantification limit (MQL) were calculated for each sample as 3 and 10 times the standard deviation for the lowest concentration (0.1 ng/mL) in a spiked infusion sample, respectively (Table 1). Low MDLs were found for both analytes (0.02-0.04 for atropine and 0.05 for scopolamine) and MQLs below 0.18 ng/mL for both atropine and scopolamine. These values are lower than the maximum level for liquid herbal infusions (0.2 ng/mL expressed as the sum of atropine and scopolamine) established in Commission Regulation (EU) 2021/1408 [29]. The ME was also estimated by comparing the slopes of the matrix-matched calibration curve with the slope of the solvent calibration curve. The formula used was ME = ((slope matrix-matched calibration/slope solvent calibration) - 1) \(\times\) 100. The ME was not significant for atropine, as the result did not exceed 20%, as recommended by SANTE guidelines [34]. For scopolamine, a slightly positive ME was found in the case of the Tea-B-3 sample and a slightly negative ME was observed in the case of the Her-Inf-4 sample (Table 1). Selectivity was assessed for all samples studied. The uncontaminated samples were tested for the absence of a signal at all ion transitions and compared with a sample doped with atropine and scopolamine to verify the total absence of peaks at a retention time (TR) of \(\pm\)0.1 min. The contaminated samples were also tested for the absence of peaks at a TR of \(\pm\)0.1 min, and the ion transition ratios were checked in mass resolution units, showing deviations less than 30% (relative abundance). The recovery percentages for all samples under study were tested at a concentration of 2.5 ng/mL by spiking the infusions with (\(\pm\))-atropine-D3 and (\(-\))-scopolamine-D3. To perform this test, the area of two spiked infusion samples (pre-extraction spike) was compared with the area of a spiked extract (post-extraction spike). The results demonstrated good application of the methodology optimized and validated by our group for all types of infusion samples [30]. As seen in Table 2, the recovery percentages were 89-109% for atropine and 73-114% for scopolamine. These values are acceptable because they are between 70 and 120%, as specified by SANTE validation guidelines [34].