For the determination of the limit of detection (LOD) and limit of quantification (LOQ), serial dilutions of the sample were prepared from higher to lower concentrations: 100 μg/mL, 5 μg/mL, 4 μg/mL, 3 μg/mL, 2 μg/mL, and 1 μg/mL. The coefficient of variance among the serial dilutions was calculated. These standards were injected in duplicate in sequence, and the correlation coefficient was determined.