2.1. Chemicals

Acetonitrile, hydrochloric acid (37 wt.%), ethyl acetate, and methanol were purchased from VWR International GmbH (Darmstadt, Germany). 2,2′-Azinobis(3-ethylbenzothiazoline-6-suflonate) (ABTS), furfural (FF, furan-2-carbaldehyde), maltol (MAL, 3-hydroxy-2-methyl-pyran-2-one), methylglyoxal (MGO, 2-oxopropanal) (40 wt.%), norfuraneol (NF, 4-hydroxy-5-methyl-3-(2H)-furanone), potassium persulfate, and trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) were purchased from Sigma-Aldrich GmbH (Steinheim, Germany). Potassium dihydrogen phosphate and potassium hydrogen phosphate were purchased from Merck KGaA (Darmstadt, Germany). 2,2-Diphenyl-1-picrylhydrazyl radical was purchased from TCI International GmbH (Hamburg, Germany). Pyrrole-2-carbaldehyde (PA, 1H-pyrrole-2-carbaldehyde) was purchased from Acros Organics N.V. (Geel, Belgium). Sodium hydroxide pellets were purchased from Carl Roth GmbH + Co. KG (Karlsruhe, Germany).