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Yessotoxins (YTXs) are a group of polyether toxins which have been previously reported as responsible for seafood contamination in several places worldwide. Despite their toxicity, which is not yet fully discussed, YTXs have been reported as an interference in the success of mouse bioassay for the determination of diarrhetic shellfish poisoning (DSP) toxins, and therefore, efficient and reliable analytical methodologies are required to evaluate their presence, avoiding false positives for DSP. High-performance capillary electrophoresis (HPCE) is presented in this work as an alternative to HPLC technique widely used for the analysis of YTXs. Improvements in the applicability of HPCE have been carried out through the development of different CE modes as well as different detection modes. With this aim, micellar electrokinetic chromatography (MEKC) has been considered for an increased selectivity while an increased sensitivity was achieved by using sample stacking. Moreover, the coupling of CE with mass spectrometry allowed the confirmation of YTXs present in the contaminated samples evaluated in this work. The results obtained showed the potential of CE as an alternative to HPLC for the analysis of YTXs present in naturally contaminated samples.

Anatoxin-a is a naturally occurring, potent neurotoxin produced by some species of cyanobacteria in freshwaters. This toxin, which is a potential health hazard, especially to animals, has been determined in different biological matrices such as several cyanobacterial cultures and water samples and carps and mussels tissue using a sensitive High Performance Liquid Chromatography with Fluorescence detection method. Sonication was the technique selected for the extraction of intracellular anatoxin-a and solid phase extraction using weak cation exchange was used for the concentration and purification of the samples. 4-Fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was used to convert anatoxin into a highly fluorescent derivative. Recovery experiments were performed for each type of matrix used in this work, and adequate values were obtained (71–87%). Limits of detection for anatoxin-a were estimated to be in the ng/L and ng/g level for water and cyanobacterial samples, respectively. The results obtained were also compared with those obtained after using solid phase microextraction, as an alternative for the extraction and purification of the samples. Advantages and disadvantages regarding to the efficiency for impurities removal, simplicity and rapidity and the potential for concentration enhancement of using both methodologies have been also discussed.

The effect of pH on the oxidation of individual PSP toxins using both periodate and peroxide oxidations was studied. It was found that the optimum pH for individual toxins varied considerably. For periodate oxidations, pH 8.2 produced the maximum yield of fluorescent products for neosaxitoxin and GTX1/GTX4 while the non-hydroxylated toxins (saxitoxin, GTX2/GTX3, decarbamoyl saxitoxin, GTX5) showed optimum pHs from about pH 10-11.5. Neosaxitoxin and GTX1/GTX4 did not produce significant fluorescent oxidation products with peroxide oxidation at any of the pHs studied (pH 8.2-12.8). The non-hydroxylated toxins all showed optimum pHs above pH 12 with peroxide oxidation. Yields of fluorescent products of these toxins decreased substantially at pHs below pH 12. Neosaxitoxin and GTX1/GTX4 each produced three product peaks at pH 8.2 with periodate oxidation. There was no pH where these toxins produced predominantly a single oxidation product. Decarbamoyl saxitoxin always produced two oxidation products with both oxidation reactions at the pHs studied. However, the relative yields of the products changed with pH. At low pH the second eluting product predominated, while at higher pH values the first eluting product predominated. This pattern was observed for both oxidation reactions. The other non-hydroxylated toxins produced mainly single unique products with both oxidation reactions over the pH range studied. No single pH was found optimum for the oxidation of both hydroxylated and non-hydroxylated toxins without a significant compromise in yield of oxidation products. This has implications for the post column oxidation liquid chromatographic methods, since small changes in pH of the post column oxidant can both positively and negatively affect the yields of oxidation products of toxin mixtures leading to increased error in the subsequent quantitation of these compounds.

Domoic acid (DA) is a neurotoxic amino acid that is responsible for the human toxic syndrome, amnesic shellfish poisoning (ASP). A new rapid, sensitive liquid chromatographic (LC) method has been developed for the determination of DA in various marine samples. DA in marine biological materials was derivatised with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and analysed using isocratic reversed-phase LC with fluorimetric detection. The calibration, based on standard DA solutions, was linear in the range 0.04–2 μg/ml ( r 2 =0.998) and the detection limit (3:1, signal/noise) was better than 1 ng/ml. Using the certified reference material (MUS-1B), recoveries of DA from shellfish tissue were >95% ( n =5). When a strong anion exchange SPE cartridge was used for sample clean-up the detection limit was 6 ng DA/g mussel tissue. Good reproducibility was achieved with RSD values ranging from 3% for 8 μg DA/g ( n =5), to 5% for 0.04 μg DA/g ( n =5). This new method was successfully applied to the determination of DA in naturally contaminated shellfish and in marine phytoplankton cultures of Pseudonitzschia sp.