Bovine plasma from control group where EC was not detected using the current method was spiked with 20 µL of EC standard solutions with concentrations ranged from 0 to 800 ng/mL in water to obtain a final EC concentrations in plasma at 0, 0.15, 0.3, 0.6, 1.2, 2.4, 4.8, 9.5, 19, 38 ng/mL, which were then extracted as described above. The calibration curves for distillers grains samples used pure water as the matrix. Limit of detection (LOD) and limit of quantification (LOQ) were calculated as 3 times and 10 times, respectively, of the standard deviation of the blank injections (i.e., contained IS but no EC) divided by the slope of the calibration curve's regression line.