*2.6. Method Validation for Quality Assurance*

The analytical method was validated using the following parameters: matrix-dependent limits of quantitation (MLOQs), linearity of matrix-matched calibration curve, and recovery efficiencies, as recommended by the European SANTE/12682/2019 guideline [15]. The instrumental limit of quantitation (ILOQ) was the concentration level with signal-to-noise (S/N) ratio of 10. ILOQ of fluopyram was computed by analyzing matrix-matched working solutions at 0.01–10 μg/L. The MLOQs were determined from the ILOQ, injection volume, dilution factor, sample amount, and extract solvent volume [16]. The linearity was evaluated using the linear regression and coefficient of determination (R2) at 1–100 μg/L of the matrix-matched working solutions. A calibration curve using matrix-matched working solutions was utilized to quantify the amount of fluopyram in the soil or scallion samples using an external standard calibration method. Procedural blanks and spiked blanks were included as quality control (QC) samples in each batch instrumental analysis. Recovery efficiency assays were performed by spiking standard solutions into control samples at 0.01 (MLOQ), 0.1 (10 MLOQ), and 1.0 (100 MLOQ, only soil) mg/kg, in triplicate. The mean and relative standard deviation (RSD) of the recovery efficiency were calculated to evaluate the accuracy and precision of the analytical method.
