Variables: pH Keywords: monitoring Substances: 18-beta-Glycyrrhetinic acid (MPDGHEJMBKOTSU-YKLVYJNSSA-N) 2-4-dimethylphenylformamide (JOFDPSBOUCXJCC-UHFFFAOYSA-N) 5-Methyl-Benzotriazole (LRUDIIUSNGCQKF-UHFFFAOYSA-N)