Un nouvel outil dans l'identification et la quantification des dinophysistoxines (DTXs) : le couplage Chromatographie Liquide Haute Performance / Spectrométrie de masse par piégeage d'ions quadripôlaire et interface d'électro- nébulisation (CLHP/SM2)

This report presents a new method for detection and confirmed quantification of dinophysistoxins (DTXs) using high-performance liquid chromatography coupled to mass spectrometry with an ion trap and électrospray interface (HPLC/ESI/MS2). The parameters of the ESI source and ion trap spectrum analyser were optimised to provide detection of DTXs with maximum sensitivity. These improvements were obtained after reverse-phase separation on a C18 column, with a first elution to 0.1% TFA (75:25, v/v) in isocratic acetonitrile/water mode without flow split at a column flow rate of 200 µl/min for 15 min. A second elution gradient step was added to allow optimised processing of long series of analyses without signal obstruction. This method was validated (specificity, detection and quantitation limits, linearity, accuracy) on two different matrices: mussel digestive glands analysed after a classical liquid/liquid extraction procedure and natural phytoplankton analysed after extraction in solid phase on silica cartridges. In comparison with HPLC by spectrofluorescence detection (HPLC/F), the sensitivity of this method reduced quantification limits from 0.5 to 0.05 injected ng, i.e. allowing detection of 0.011 µg.g-1 okadaic acid (OA) from 4 g of crude mussel digestive gland extract. For a crude phytoplankton extract of Dinophysis spp at 50 cells/litre, 2 pg.cell-1 OA can be detected.