Determination of Ochratoxin A in beer samples by a novel and practical SALLE-based approach prior to UHPLC-MS/MS

MARIÑO L; GOICOECHEA, H C; RABA J; CERUTTI S

Workshop; VIII Workshop de Quimiometria; 2017

Ochratoxin A (OTA) is a toxic compound, initiator, promoter of cancers and endemic diseases. OTA contamination might occur when the ochratoxigenic fungi infect the cereal crops (mostly barley and wheat), during their cultivation and until post-harvest1. Thus, beer might contain OTA traces since brewing, cereals (malt) might be contaminated2. Therefore, some countries have established maximum allowable limits (MALs) to reduce OTA intake from beer (0.2 µg L-1)3. For that reason, simple, effective and sensitive methods for OTA determination at low concentration levels are necessary4. Hence, a novel sample treatment methodology based on salting-out assisted liquid-liquid extraction (SALLE) was optimized using a multivariate design of experiments strategy and, then coupled to ultra-high performance liquid chromatography-tandem mass spectrometryResults and DiscussionSALLE is a sample treatment based on the use of a salt and hydrophilic solvents to induce, by sating-out, liquid phase?s separation. In this work, the variables affecting the SALLE procedure, such as salt type, hydrophilic and nonpolar solvents were evaluated for further optimization. Thus (NH4)2SO4, acetone, and toluene were employed in SALLE experiments. Then, a fractional factorial design (2k-p) was evaluated to assess significant factors, such as: mass of (NH4)2SO4 and acetone, toluene and sample volumes together with centrifugation and vortexing times. From the obtained results, except for the mass of (NH4)2SO4, all the tested factors were statistically significant. In order to continue with the optimization, a full factorial design (2k) was performed, from where factors and curvature resulted significant. Then, the conditions were furtherly optimized using a central composite design and the desirability function. The methodology was validated, and the limit of detection was calculated (0.017 µg L-1), which was considerably lower than the established MAL; also, the precision and accuracy were in agreement with current normatives6. Also, the matrix effect on OTA?s signal was studied and, applying the sample treatment the signal suppression was reduced to only 15%. Finally, different types of beer samples were analyzed. OTA concentration levels were found to be below the MAL value.