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A high-performance liquid chromatography method with fluorescence detection (HPLC-FLD) was developed and validated for the detection of zearalenone (ZON), alpha-zearalenol (alpha-ZOL) and beta-zearalenol (beta-ZOL) in in vitro biological samples. Furthermore, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the detection of ZON, alpha-ZOL, beta-ZOL, alpha-zearalanol (alpha-ZAL) and beta-zearalanol (beta-ZAL) in in vitro biological samples. Zearalanone (ZAN) was used as internal standard in both methods. The limit of detection/limit of quantitation (LOD/LOQ) values for ZON, alpha-ZOL and beta-ZOL were 2/7, 2/7 and 4/13 microg l(-1), respectively, for the HPLC-FLD method. For the LC-MS/MS method LOD/LOQ values for ZON, alpha-ZOL, beta-ZOL, alpha-ZAL and beta-ZAL were 6/20, 5/17, 4/14, 9/30 and 6/19 microg l(-1), respectively. Within-day and between-day precision were less then 11 and 14%, respectively for the HPLC-FLD method, and both less then 20% for the LC-MS/MS method. The recovery of ZON and its metabolites ranged between 73 and 89% for the HPLC-FLD method and between 69 and 112% for the LC-MS/MS method. The methods were used for the detection of the compounds in in vitro biological samples, obtained with human intestinal Caco-2 cells culture experiments. The 8-days post-confluent Caco-2 cells were treated with ZON or a mixture of ZON and imazalil (IMA). After an incubation time of 24 h the samples were analysed with the HPLC-FLD method. Neither ZON nor its derivatives were detected in the samples. The disappearance of ZON could possibly point out the formation of phase II metabolites like glucuronide conjugates. Therefore, samples were pretreated with beta-glucuronidase before LC-MS/MS analysis. The LC-MS/MS results showed that ZON, alpha-ZOL and beta-ZOL could only be detected in the beta-glucuronidase pretreated samples. This confirmed the formation of glucuronide conjugates and the hydroxylation of ZON during the incubation with Caco-2 cells.

Liquid chromatographic methods were used for the detection of ochratoxin A (OTA) and its metabolites ochratoxin alpha (OTalpha), 10-hydroxy OTA (10-OHOTA), 4R-hydroxy OTA (4R-OHOTA) and the ethyl ester of OTA (OTC) in in vitro samples, obtained with Caco-2 cell culture experiments and in in vivo urine samples from sheep. A high-performance liquid chromatography method with fluorescence detection (HPLC-FLD) and a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method were developed and validated for the detection of OTA and its metabolites OTalpha, 10-OHOTA, 4R-OHOTA and OTC, which was used as internal standard. The LOD/LOQ values for OTalpha, 4R-OHOTA and OTA were 0.63/2.11, 0.99/3.31 and 0.84/2.81 microg/L, respectively, for the HPLC-FLD method and 0.98/3.28, 1.11/3.72 and 0.88/2.96 microg/L, respectively for the LC-MS/MS method. Within-day and between-day precision were both <12% for the HPLC-FLD method, and <10% for the LC-MS/MS method. The recovery of OTA and its metabolites ranged between 71 and 111% for the HPLC-FLD method and between 79 and 110% for the LC-MS/MS method. In the first experiment only OTA was added to the Caco-2 cells while in the second experiment 3-methylcholanthrene (3MC) was also present in the cell culture systems. Besides OTA, which was recovered in all the samples, an unknown compound was also observed in the second experiment. When 3MC was added, the results showed that the OTA concentration in the basolateral samples was decreased by 50%. The methods were also implemented for the analysis of urine samples of sheep, fed increasing amounts of OTA. With the HPLC-FLD method it could be concluded that the concentration of OTA and OTalpha increased according to ingested amounts of OTA, with OTalpha being the most abundant compound. The results obtained with the LC-MS/MS method confirmed these results.