Assay of ochratoxin A in grape by high-pressure liquid chromatography coupled on line with an ESI–mass spectrometry

In this paper, we propose a method for detection of ochratoxin A (OTA) in grapes by using nano-reversed-phase high-performance liquid chromatography–electrospray ionization–mass spectrometry (nano-RP-HPLC–ESI–MS). The method is rapid, highly sensitive and reproducible. OTA is extracted preferably from the entire acinus, rather than must; using chloroform at long incubation time period, lyophilized, resolubilized in acetonitrile (AcCN) and injected onto a reversed phase capillary or analytical column. Capillary columns are the method of choice because it requires a reduced amount of injected sample and consequently the chloroform necessary for OTA extraction, which is a toxic agent. This method gives a detection limit of femtog/ml, without resorting to an immunoaffinity clean-up or concentration, which makes it by far superior to any other method reported. Moreover, by using MS as a detection method it is possible, in the case of a complex matrix, to measure its molecular mass and to confirm the presence of OTA by MS–MS, which cannot be done by fluorescent detection. The method has a high sample extraction throughput (24/h) and has adequate precision (between batch C.V. <8%) and sensitivity (limit of detection (LOD) = 1 pg/g; limits of quantification (LOQ) = 2 pg/g) for OTA measured.