Variables: concentration Substances: 18-beta-Glycyrrhetinic acid (MPDGHEJMBKOTSU-YKLVYJNSSA-N) MCPA (WHKUVVPPKQRRBV-UHFFFAOYSA-N) 1-Propanesulfonate (KCXFHTAICRTXLI-UHFFFAOYSA-N) Keywords: high resolution mass spectrometry