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.

Quantification of mycotoxins in vegetable oil by UPLC-MS/MS after magnetic solid-phase extraction

“…It was suggested that the amine group of the mycotoxins could bound to the free silanol groups on the glass surface of the used test tubes. The loss level was lower than the results reported previously, which was up to 75% (Nielsen et al 2015). Therefore, we selected the method of dilution of the MSPE eluate instead of evaporation.…”

Developments in mycotoxin analysis: an update for 2017-2018

“…Although satisfactory analytical performances were reported in terms of recoveries and repeatability, application of the proposed method to naturally contaminated samples was not investigated. Nielsen et al (2015) reported on the development of a LC-MS/MS method for simultaneous determination of OTA and fumonisins B 2 , B 4 (FB 4 ), and B 6 (FB 6 ) in green, roasted, and instant coffee. To maximise recoveries of these toxins containing acidic functional groups, extraction was performed by an acidified water/methanol mixture followed by mixed-mode reversed phase-anion exchange SPE (Oasis MAX® cartridges).…”

“…Extraction using QuEChERS-type procedures have previously been applied to fumonisins in various commodities. Recently, the technique, in combination with mixed-mode SPE was used to isolate FB 2 , FB 4 , FB 6 , and OTA from green, roasted, or instant coffee (Nielsen et al, 2015). Using an isotopic internal standard, the LOD of the method was 2 µg/kg.…”

The importance of mass spectrometric dereplication in fungal secondary metabolite analysis

“…Acid catalyzed reactions can be especially problematic when evaporating organic extracts, since the lower volatility of acids such as formic and acetic acids will result in upconcentration when using volatile solvents like EtOAc and DCM, especially in the presence of residual water. Examples we have observed include; up to 50% loss of patulin during evaporation from EtOAc ( Boonzaaijer et al, 2005 ); loss of trichothecenes prior to derivatization for GC-MS analysis ( Langseth and Rundberget, 1998 ); up to 80% loss of fumonisins due to binding to the silanol groups of non-derivatized glass with up to 80% lost ( Nielsen et al, 2015 ). We have used a fast extraction procedure to minimize the risk of studying artifact peaks, this procedure involves extraction into acetonitrile-water (1:1; in a ultrasonication bath or a beadbeater for circa 10 min), followed by centrifugation and subsequent transfer of the centrifugate directly to an auto-sampler compatible vial for analysis ( Mogensen et al, 2011 ).…”