Evaluation of a postcolumn electrochemical reactor for oxidation of paralytic shellfish poison toxins

A liquid chromatographic method using a postcolumn electrochemical reactor that oxidizes paralytic shellfish poison toxins to fluorescent derivatives has been developed. Several experimental parameters, including pH and oxidation potential, were investigated. For nonhydroxylated toxins, the sensitivity improved with increasing pH and voltage. At optimum operating conditions, the sensitivity for saxitoxin and gonyautoxins 2 and 3 was an order of magnitude greater than that for neosaxitoxin and B1 and 2 orders of magnitude greater than that for B2. The limit of detection for saxitoxin was 0.10 ng (signal-to-noise ratio, 3:1). Electrochemical oxidation products were similar to those formed in the prechromatographic periodate oxidation method. Shellfish and plankton extracts were analyzed with the electrochemical system, and results agreed well with those obtained with established methods. Shellfish samples contaminated at the regulatory limit of 0.8 microgram/g were readily analyzed by the method.