The challenge to work with bovine plasma with low EC concentration was to confirm the EC peak identity because matrix noise significantly interfered with the confirmation ions m/z 44 and m/z 74 when EC <2 ng/mL. Parent ion M +ꞏ m/z 89 is too weak under electron impact ionization to be used for confirmation. Thus, APGC-qTOF with soft ionization technology and high resolution mass spectrometer was used to obtain the accurate mass of the parent ion of EC to confirm its presence in the actual plasma samples. The corona pin current and cone voltages were optimized to improve EC ionization. A polar solvent methanol with 10% acetic acid was used as proton donor to assist the ionization and increase the signal intensity of [M+H] + . The solution's vial position on the source housing, hot versus cold spot, was also optimized. A mass error of 2.2 ppm was obtained for [M+H] + m/z 90.056 of EC extracted from the test group bovine plasma (Figure ), adding additional confirmation of the identity of EC in animal biofluids after consumption of distillers grains co-products.