Evaluation of prechromatographic oxidation for liquid chromatographic determination of paralytic shellfish poisons in...

A liquid chromatographic (LC) method employing prechromatographic oxidation for the determination of paralytic shellfish poison (PSP) toxins was evaluated. A number of changes to an earlier method resulted in improved separation and quantitation of most PSP analogues. Modification of the periodate oxidation reaction for the N-hydroxy-containing toxins led to improved sensitivity and stability of the products, enabling automated overnight analyses. These changes also enabled quantitation of gonyautoxins 1 and 4 (together) in the presence of gonyautoxins 2 and 3. Decarbamoylsaxitoxin can be identified and quantitated after peroxide oxidation. A cleanup step using a strong-anion-exchange column removed the C toxins and B-2 from the extracts and enabled a more accurate quantitation of gonyautoxins 1 and 4 and neosaxitoxin. Chiral chromatography, employing a reversed-phase column and chiral mobile-phase additives (copper-proline complex), was briefly evaluated for the separation of the oxidation products of the isomer pairs, gonyautoxins 1 and 4 and gonyautoxins 2 and 3. A comparison of the method with the mouse bioassay for the determination of PSP in lobster hepatopancreas (58 samples) showed a reasonable correlation (0.90) over a concentration range of 40-500 micrograms/100 g (saxitoxin equivalents), although the LC results were consistently higher than the mouse bioassay values by about 40%.