A rapid qualitative screening method was developed for the fractionation of paralytic shellfish poisoning toxins. Periodic acid, t-butyl hydroperoxide, and hydrogen peroxide were tested as oxidants for the fluorometric detection of paralytic shellfish toxins. Hydrogen peroxide was found to be the most convenient and efficient oxidant since the fluorescence can be detected after the incubation of toxins at 100 degrees C for 3-5 min. In addition to the structure of the compound, the incubation temperature and time, the amount of acid, and the peroxide concentration affect the fluorescence reaction. This method was more efficient than the previously published peroxidation methods which involved lengthy incubation periods or time-consuming pH adjustment. Also, far greater sensitivity was achieved with the new method with levels of 0.027, 0.054, 0.023, 0.003, 0.0002, and 0.0006 pmol being easily detected for saxitoxin, neosaxitoxin, gonyautoxin 1 and 4, gonyautoxin 2 and 3, C toxins, and B toxins, respectively. The method is particularly valuable for the screening of fractions separated by column chromatography.