In the partition phase of the QuEChERS method the addition of
anhydrous inorganic salts (MgSO4 and NaCl) was selected in order
to separate aqueous from the organic solvent phase. Then, the upper
organic layer containing the target analytes was subjected to a
dispersive clean-up step by using PSA and MgSO4. A preliminary
screening was carried out with different volumes of acetonitrile
extracts (2, 4 and 6 ml) and amounts of added PSA sorbent (50
and 60 mg PSA/ml extract) to assess the clean-up efficiency. The
addition of 50 mg PSA per milliliter of extract in 4 ml of supernatant
was found optimal, resulting in less co-extracted substances and
better chromatographic performance. Graphitized carbon black
(GCB), a common sorbent in the original QuEChERS method, was
not used due to the sorption of the target mycotoxins resulting in
lower recovery values. Mycotoxins adsorption on graphitized carbon
black has also been reported by other researchers (Tamura,
Uyama, & Mochizuki, 2011).