Supramolecular solvent-based microextraction of ochratoxin A in raw wheat prior to liquid chromatography-fluorescence determination
Autor
García-Fonseca, S.
Ballesteros-Gómez, A.
Rubio Bravo, Soledad
Pérez-Bendito, Dolores
Editor
ElsevierFecha
2010Materia
WheatSupramolecular solvent
Ochratoxin A
Liquid chromatography
Fluorescence detection
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A supramolecular solvent made up of reverse micelles of decanoic acid, dispersed in a continuous phase
of THF:water, was proposed for the simple, fast and efficient microextraction of OTA in wheat prior
to liquid chromatography-fluorescence determination. The method involved the stirring of 300 mgwheat
subsamples (particle size 50 um) and 350 uL of supramolecular solvent for 15 min, subsequent
centrifugation for 15 min and the direct quantitation of OTA in the extract, previous 5.7-fold dilution
with ethanol/water/acetic acid (49.5/49.5/1), against solvent-based calibration curves. No clean-up of
the extracts or solvent evaporation was needed. Interactions between the supramolecular solvent and
major matrix components in the wheat (i.e. carbohydrates, lipids and proteins) were investigated. The
reverse micelles in the extractant induced gluten flocculation but only in the coacervation region of lower
analytical interest (i.e. at percentages of THF above 11%). The quantitation of OTA was interference-free.
Representativity of the 300 mg-wheat subsamples was proved by analysing a reference material. OTA
recoveries in wheat ranged between 84% and 95% and the precision of the method, expressed as relative
standard deviation, was 2%. The quantitation limit of the method was 1.5 ug/kg and was below the
threshold limit established for OTA in raw cereals by EU directives (5.0 ug/kg). The method developed
was validated by using a certified reference material and it was successfully applied to the determination
of OTA in different wheat varieties from crops harvested in the South of Spain. OTA was not detected in
any of the analysed samples. This method allows quick and simple microextraction of OTA with minimal
solvent consumption, while delivering accurate and precise data.