The extraction of ZEA followed the procedure described by Domijan et al. (2005). Wheat flour samples (4 g) were extracted three times with dichloromethane and the clean-up procedure was performed on SPE cartridges (Bond Elut C-18, Varian, Harbor City, CA, USA). ZEA was eluted from the SPE columns with methanol and the eluate was evaporated to dryness under a gentle stream of nitrogen in a water bath at 60 C. The sample was redissolved in the mobile phase, and 20 ml was injected onto the HPLC. The mobile phase consisted of methanol and water (80:20). The flow rate of the mobile phase was 0.5 ml min 1 . The guard column
and the analytical column were LiChrospher RP-18 (Merck, Darmstadt, Germany) with 5 mm particles, and their sizes were 4.0 4.0 and 250.0 4.0 mm, respectively. The wavelengths of the detector were set at 274 nm (kex) and 440 nm (k
em). The linearity of the standard curve ( r2) was 0.9992. The detection limit was
0.39 mg kg 1, recovery 108% and reproducibility, expressed as RSD was 5.6%.