Determination of Six Priority Phthalates and Di(Ethylhexyl) Adipate in Maize Tortilla by Gas Chromatography - Tandem Mass Spectrometry in Multiple Reaction Monitoring Mode

The term “phthalates” refers to a group of esters of benzene-1,2-dicarboxylic acid, widely used as plasticizers therefore ubiquitous in food and in the environment. Several phthalates have been cataloged as endocrine disruptors and that is why there is a strong demand for their reliable determination, especially in food matrices.  In the present work, gas chromatography - tandem mass spectrometry (GC-MS/MS) procedure is proposed for the determination of six priority phthalates (dimethyl phthalate DMP, diethyl phthalate DEP, di(n-butyl) phthalate DBP, benzyl butyl phthalate BBP, di(2-ethylhexyl) phthalate DEHP, di(n-octyl) phthalate DnOP) and di(2-ethylhexyl) adipate DEHA, in maize tortillas and flour. Fresh tortilla sample was homogenized with acetonitrile/water (1:1) and after salting out (NaCl), hexane extract was obtained and dried by addition of Na 2 SO 4 anhydride. Finally, solvent was evaporated and the residue was reconstituted in isooctane for the injection to GC-MS/MS system; a model SCION GC-TQMS from Bruker Daltonics was used for the analysis. Quantification was carried out by multiple reaction monitoring (MRM) with the following time segments and m/z values of the precursor/product ion transitions: 0-7.90 min, 163/133 DMP; 7.47-8.53min, 149/121 DEP; 8.53-9.93 min, 149/121 DBP; 9.93-12.39 min, 149/93 BBP; 11.40-12.44 min, 129/111 DEHA; 12.20-13.22 min, 149/121 DEHP; 13.13-14.20 min, 149/121 DnOP. The evaluated method detection limits for seven compounds were in the range 0.11-1.84 µg kg -1 (tortilla dry mass). The results obtained for fifteen tortilla samples purchased in Guanajuato state were as follows: 71.6-420 µg kg -1 DEHP > not detected (nd)-274 µg kg -1 DBP > nd-197 µg kg -1 DEHA > nd-73.2 µg kg -1 DEP > nd-10.6 µg kg -1 DnOP. It was observed that prolonged storage and elevated temperature favored the accumulation of phthalates in tortillas.