Abstract
Paralytic shellfish toxins (PST) traditionally have been analyzed by liquid chromatography with either pre- or post-column derivatization and always with a silica-based stationary phase. This technique resulted in different methods that need more than one run to analyze the toxins. Furthermore, tetrodotoxin (TTX) was recently found in bivalves of northward locations in Europe due to climate change, so it is important to analyze it along with PST because their signs of toxicity are similar in the bioassay. The methods described here detail a new approach to eliminate different runs, by using a new porous graphitic carbon stationary phase. Firstly we describe the separation of 13 PST that belong to different groups, taking into account the side-chains of substituents, in one single run of less than 30 min with good reproducibility. The method was assayed in four shellfish matrices: mussel (Mytillus galloprovincialis), clam (Pecten maximus), scallop (Ruditapes decussatus) and oyster (Ostrea edulis). The results for all of the parameters studied are provided, and the detection limits for the majority of toxins were improved with regard to previous liquid chromatography methods: the lowest values were those for decarbamoyl-gonyautoxin 2 (dcGTX2) and gonyautoxin 2 (GTX2) in mussel (0.0001 mg saxitoxin (STX)·diHCl kg−1 for each toxin), decarbamoyl-saxitoxin (dcSTX) in clam (0.0003 mg STX·diHCl kg−1), N-sulfocarbamoyl-gonyautoxins 2 and 3 (C1 and C2) in scallop (0.0001 mg STX·diHCl kg−1 for each toxin) and dcSTX (0.0003 mg STX·diHCl kg−1 ) in oyster; gonyautoxin 2 (GTX2) showed the highest limit of detection in oyster (0.0366 mg STX·diHCl kg−1). Secondly, we propose a modification of the method for the simultaneous analysis of PST and TTX, with some minor changes in the solvent gradient, although the detection limit for TTX does not allow its use nowadays for regulatory purposes.
Highlights
Marine biotoxins are produced by more than 200 marine algal species
The initial chromatographic conditions for post-column oxidation (PCOX) separation of Paralytic shellfish toxins (PST) were those reported by Van de Riet et al [22], several modifications were accomplished: the column and mobile phase were different
While in PCOX the separation is based on the use of heptane sulfonate and tetrabutyl ammonium phosphate, in this case, the mobile phase was based on the use of trifluoroacetic acid (TFA)
Summary
Marine biotoxins are produced by more than 200 marine algal species. They are complex secondary metabolite molecules with high toxicity and an unknown physiological role. The intake of these compounds can lead to serious toxic effects in humans, including death [1,2]. Paralytic shellfish toxins (PST) cause persistent problems in humans due to their accumulation in filter feeding shellfish [3], but they can move up through the food chain, affecting zooplankton, fish, birds and marine mammals [4]. PST intoxications are a result of exposure to saxitoxins (STXs), gonyautoxins (GTXs) and N-sulfocarbamoyl-gonyautoxins (Cs). More than 57 different analogues of saxitoxin (STX) have been described to date [5,6]
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