| The entire research work in the present study has been divided into 5 parts, and presented as 5 chapters with different objectives and an abstract in each chapter. In the first part, a rapid qualitative method was developed for the fractionation of paralytic shellfish poisoning toxins. Periodic acid, t-butyl hydroperoxide and hydrogen peroxide were tested as oxidants, and hydrogen peroxide was found to be the most convenient and efficient oxidant for the fluorometric detection of paralytic shellfish poisoning toxins. The fluorescence could be detected after incubation of toxins at 100°C for 3--5 min. This method was more efficient than the previously published peroxidation methods which involved lengthy incubation periods or time consuming pH adjustment. Individual toxins were detected in pico molar levels.; The second part involves the use of thin layer chromatography on Chromarods-SIII with the Iatroscan (Mk 5) and a flame thermionic detector (FTID) to develop a rapid method for the detection of PSP toxins and separate major compounds. Air and hydrogen flow, detector current and scan time were found to affect the FTID response of all PSP compounds. Quantities of toxin standards as small as 1--6 ng could be detected. Among numerous solvent systems tested, a mixture consisting of chloroform: methanol water : acetic acid (30:50:8:2) could separate C toxins from gonyautoxins (GM, which eluted ahead of neosaxitoxin (NEO) and saxitoxin (STX), and STX did not migrate.; The kinetics of thermal degradation of PSP toxins in scallop digestive glands were studied in part 3. Scallop homogenates were heated at different pH levels (3--7) for different times at 90, 100, 110, 120 and 130°C. All toxins were sensitive to higher temperatures and higher pH values, and the kinetics of thermal destruction were qualitatively similar to the thermal destruction of microorganisms. The levels of individual toxins in the homogenate and those generated during heating could be reduced significantly by heating at 130°C at pH 6--7. Studies on the thermal degradation of PSP toxins were continued in the same manner using a mixture of purified and partially purified toxins, instead of homogenate, in the fourth part. Some toxin inter-conversions as well as degradation were noticed in both situations.; The fifth part of the study was focused mainly on the storage stability of PSP toxins under different conditions. Homogenates and purified toxin mixtures heated at 120°C for 1 h as well as unheated samples were stored for 1 year and 4 months, respectively, at three temperatures (-35, 5 and 25°C). There was no significant change in any toxin type when stored at -35°, regardless of pH, whereas C toxins and GTX 1/4 decreased after 4 months at 25°C. NEO and STX levels remained unchanged at all storage temperatures at low pH levels. Purified toxins used as primary analytical standards as well as partially purified toxins and toxins in homogenized matrix, sometimes used as secondary standards, can be stored safely at pH 3 and at ≤-35°C. |
