title: UHPLC-MS/MS determination of ochratoxin A and fumonisins in coffee using QuEChERS extraction combined with mixed-mode SPE purification.
abstract: A method was developed for simultaneous determination of the mycotoxins: ochratoxin A (OTA) and fumonisins B2 (FB2), B4 (FB4), and B6 (FB6) in green, roasted, and instant coffee. Extraction was performed by QuEChERS (quick, easy, cheap, effective, rugged, and safe) under acidic conditions followed by mixed-mode reversed phase-anion exchange solid phase extraction. OTA and FB2 were detected at levels down to 0.5 and 2 μg/kg by UHPLC-MS/MS and quantitated via isotope dilution using U-(13)C-labeled FB2 and OTA as internal standards. Mixing 20% isopropanol in the acetonitrile of the acidic UHPLC gradient system increased the signal intensity by 50% and decreased the ion-suppression with 50-75% in roasted coffee samples. About half of the roasted coffee samples (n = 57, from 9 countries) contained detectable levels of OTA, however, with only 5 samples above the EU regulatory limit of 5 μg/kg and the highest with 21 μg/kg. None of the 25 instant coffee samples contained OTA above the EU regulatory level of 10 μg/kg. Nonetheless, the toxin could be detected in 56% of the analyzed instant coffee samples. Fumonisins were not detected in any of the roasted or instant coffee samples (n = 82). However, in the green coffee samples (n = 18) almost half of the samples were positive with a maximum value of 164 μg/kg (sum of FB2, FB4, and FB6). This discrepancy between green coffee and processed coffees indicated that the fumonisins decompose during the roasting process, which was confirmed in roasting experiments. Here fumonisins could not be detected after roasting of the green, 164 μg/kg coffee, sample. Under the same conditions, OTA was reduced from 2.4 to 0.5 μg/kg.
authors.affiliation: Department of Systems Biology, Technical University of Denmark , Building 221, 2800 Lyngby, Denmark.
authors.forename: Kristian Fog
authors.initials: KF
authors.lastname: Nielsen
authors.forename: Archard Ferdinand
authors.initials: AF
authors.lastname: Ngemela
authors.forename: Lene Bai
authors.initials: LB
authors.lastname: Jensen
authors.forename: Lívia Soman
authors.initials: LS
authors.lastname: de Medeiros
authors.forename: Peter Have
authors.initials: PH
authors.lastname: Rasmussen
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D040503:Coffea / Q000737:chemistry* / Q000382:microbiology; D003718:Denmark; D005511:Food Handling / Q000379:methods; D037341:Fumonisins / Q000032:analysis*; D009793:Ochratoxins / Q000032:analysis*; D010936:Plant Extracts / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry; D052616:Solid Phase Extraction / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D037341:Fumonisins; D009793:Ochratoxins; D010936:Plant Extracts; C548017:fumonisin B6; C056934:fumonisin B2; C076287:fumonisin B4; C025589:ochratoxin A
keywords: Aspergillus niger; LC-MS/MS; QuEChERS; coffee; fumonisin; isotope dilution; mixed-mode reversed phase-anion exchange; ochratoxin A