*3.3. Method Validation for Quantitative Analysis of Five Flavonoids*

Table 3 listed the linear equation, correlation coefficient (*R*2), linear range, LOD, and LOQ of each compound determined. It could be found that all calibration curves showed good linearity (*R*<sup>2</sup> <sup>≥</sup> 0.9995) within the tested concentration range. For these compounds, the LOD values ranged from 0.014 to 0.094 μg/mL, while the LOQ values ranged from 0.16 to 1.31 μg/mL. The results of precision, stability, and accuracy tests were shown in Table 4. All RSD values of the intra-day and inter-day precision ranged from 0.94–2.43% and 1.87–2.51%, respectively, which indicated good precision of the developed method. The results of the stability test showed that the RSD values of peak areas of the five compounds were ≤2.56%, which indicated that the sample was stable for 12 h at room temperature. According to the calculation, the mean recoveries of five compounds ranged from 98.93 to 101.3%, with RSD values ranging from 0.85 to 2.19%, which demonstrated a good accuracy of the developed method. In sum, the verification tests demonstrated that the developed method was feasible for the simultaneous quantification of five compounds from *P. cretica*.

**Table 3.** Linear regression, limit of detection (LOD), and limit of quantification (LOQ) of the five tested compounds.



**Table 4.** Precision, stability, and recovery of the five tested compounds.
