Sinigrin potassium salt

Sinigrin potassium salt (≥95.0%), imidazole formate (≥94%), DEAE Sepharose CL-6B suspension and sulfatase (from Helix pomatia, Type H-2, aqueous solution, ≥2000 units/mL), and certified rapeseeds (ERM-BC367) were purchased from Sigma-Aldrich (St. Louis, MO, USA). The sulfatase was diluted 100-fold with ultrapure water to a working solution. Formic acid and liquid chromatography-mass spectrometry (LC-MS) grade acetonitrile were purchased from Fisher Scientific (Waltham, MA, USA). Ultrapure water was prepared from distilled water using a Milli-Q system (Millipore Lab., Bedford, MA, USA). All other chemicals and reagents were of analytical grade.

The reference compounds (3-isothiocyanatoprop-1-ene (CAS 57-06-7), but-3-enenitrile (CAS 109-75-1), isothiocyanatomethylbenzene (CAS 622-78-6), 2-phenylacetonitrile (CAS 140-29-4)) of the highest available GC purity (>98%) were obtained from Sigma-Aldrich (Poznań, Poland). Thioglucosidase from Sinapis alba, sinigrin potassium salt, anhydrous sodium sulfate, iron(II) sulfate heptahydrate, SPME fiber divinylbenzene/ carboxen/polydimethylsiloxane (DVB/CAR/PDMS) were purchased from Sigma-Aldrich (Poznań, Poland), glucotropaeolin potassium salt was purchased from Extrasynthese (Genay Cedex, France), copper(II) sulfate pentahydrate was purchased from Chempur (Piekary Śląskie, Poland) and silver nitrate was purchased from POCh S.A. (Gliwice, Poland). Fresh kohlrabi was purchased at a local grocery store (Poznań, Poland).