Acetonitril

The dyes 7-(diethylamino)coumarin-3-carbohydrazide (DCCH, Purity 95%, CAS: 100343-98-4), fluorescein-5-thiosemicarbazide (FTSC, Purity 99%, CAS: 76863-28-0) and the standard fluorescein sodium salt were bought from Santacruz Biotechnology (Dallas, Texas, USA). Coumarin 30 was bought from (Sigma Aldrich) The solvents N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), Tetrahydrofuran (THF), and Acetonitril were purchased from VWR (Vienna, Austria). All chemicals were used without further purification.

methanol (p.a., min 99%), acetic acid (p.a., min. 99.0%), sodium acetate (anhydrous, p.a., min. 99.0%) and iron (III) chloride hexahydrate (p.a., min. 99.0%) were purchase from ChemSolute^® (Renningen, Germany). Ethyl acetate (≥99.7%, PESTINORM^®), methanol (≥99.9%, HiPerSolv CHROMANORM^®, super gradient), acetonitril (HiPerSolv CHROMANORM^® Reag, ≥99.95%, super gradient grade) were ordered from VWR International (Darmstadt, Germany). (±)-6-Hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox, 97.0%), 2,4,6-tris-(2-pyridyl)-s-triazin (TPTZ, ≥98%), sodium phosphate monobasic (p.a., anhydrous, ≥99.0%), 2,2-diphenyl-1-picrylhydrazyl (DPPH, 95%), standard flavonoids, and 2,2′-azobis-(2-methyl-propionamidine) dihydrochloride (AAPH, 97%), were purchased from Sigma-Aldrich (Schnelldorf, Germany). Furthermore, L-(+)-ascorbic acid (≥99%, p.a.), fluorescein disodium salt (C.I. 45,350) and sodium carbonate (≥99.5% anhydrous) were obtained from Carl Roth (Karlsruhe, Germany). Ethanol (absolute, min. 99.8%) was purchased from Walter-CMP (Kiel, Germany), sodium phosphate dibasic dihydrate (ultrapure, 98.5–101%) was obtained from Honeywell (Charlotte, North Carolina, United States); and hydrochloric acid (37%, p.a.) were bought from Merck (Darmstadt, Germany). Ultra-pure water was generated via Purelab Flex 3 (ELGA LabWater, Veolia Water Technologies Deutschland GmbH, Celle, Germany).