Abstract
Saxitoxin (STX) and the PSP toxins are electrochemically active with significant oxidation occurring at applied potentials greater than 0.8 volt. To test if an electrochemical cell could replace the post column reaction system (PCRS) currently used for the analysis of the shellfish toxins, a coulometric electrochemical cell operating at 0.8 v was placed after the HPLC column and prior to the fluorometric detector. The fluorescent response from this electrochemical oxidation system (ECOS) was directly compared to the PCRS as described by Sullivan. Using purified STX, the minimum detection limit for the ECOS was 0.7 pmol/20 mu l. The limit using purified NeoSTX was < 24 pmol/20 mu l. Minimum detection limits for the 11-sulfate analogs (GTX-1, GTX-2 and GTX-3), Bl and Cx were estimated using a crude dinoflagellate extract and ranged from 0.09-0.8 pmol/20 mu l. With the exception of NeoSTX, the detection limits obtained using the ECOS were not significantly different from those obtained using the PCRS. Electrochemical oxidation represents a simple modification to the HPLC method for PSP toxin detection that eliminates many of the problems associated with the current post column reactor system.