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Modification and derivatisation of lipophilic shellfish toxins to enable extract clean-up and LC-MS quantification

Project Code: P01001

20/04/2011

LGC
Dreiseidler, E ; Points, J

A theoretical reaction scheme was designed which would convert all toxins within a class to a common product for three of the four regulated lipophilic toxin classes [OA/DTXs, PTXs and (homo-)YTXs]. The scheme was not applicable to the fourth class [AZAs]. A separate theoretical scheme was proposed which would cover the most common AZAs.

The scheme is based on ozonolysis. This is an archaic technique within synthetic organic chemistry, but the equipment is cheap and the scheme has the potential to be rapid, economical and scaleable.

The scheme was applied to Vitamin D2, as a chemical that is structurally similar to okadaic acid in the key functional groups and in more abundant supply as a starting material for synthetic chemistry experiments. These experiments demonstrated that there were multiple critical parameters and variables to optimize. After some adaptation, the scheme was shown to be applicable to Vitamin D2 with a reaction yield of 30%.

The reaction conditions were optimized for okadaic acid. After some adaptation, the scheme was shown to be applicable to okadaic acid with a reaction yield of 10%. A reference standard was synthesized and certified to measure the product. The product was measured by LC-MS/MS. The signal strength would equate to a detection limit of 1 microgram per kilogram of okadaic acid in shellfish tissue if the same reaction yield and instrument response were extrapolated to sample extracts. The regulatory limit is 160 micrograms per kilogram.

The results proved that this hypothetical approach could work in principle. There would be many critical variables to optimize, and a major research programme would be needed to bring this approach to a stage where it could be applied in practice to regulatory monitoring. Success would not be guaranteed, as there are many hurdles at which such a programme could fall.

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