Quantitative determination of paralytic shellfish poisoning toxins in shellfish by using prechromatographic oxidation and liquid chromatography with fluorescence detection

The prechromatographic oxidation LC method developed by Lawrence [J. Assoc. Off. Anal. Chem. 74, 404-409(1991)] for the determination of paralytic she llfish poisoning (PSP) toxins has been tested for the quantitative determin ation of PSP toxins in shellfish. All aspects of the method were studied an d modified as necessary to improve its performance for routine regulatory p urposes. The chromatographic conditions were changed to shorten analysis ti me. The oxidation reaction was tested for repeatability and the influence o f the sample matrix on quantitation. An important part of the study was to quantitatively evaluate an ion exchange (-COOH) cleanup step using disposab le solid-phase extraction cartridges that separated the PSP toxins into 3 d istinct groups for quantitation, namely the C toxins, the GTX toxins, and t he saxitoxin group. The cleanup step was very simple and used increasing co ncentrations of aqueous NaCl for elution of the toxins. The C toxins were n ot retained by the cartridges and thus were eluted unretained with water. T he GTX toxins (GTX1 to GTX6 as well as dcGTX2 and dcGTX3) eluted from the c artridges with 0.05M NaCl while the saxitoxin group (saxitoxin, neosaxitoxi n, and dcsaxitoxin) required 0.3M NaCl for elution. Each fraction was analy zed by LC after oxidation with periodate or peroxide. All of the compounds could be separated and quantitatively determined in spiked samples of musse ls, clams, and oysters. The nonhydroxylated toxins could be quantitated at concentrations as low as about 0.02 mug/g (2 mug/100 g) of tissue while the hydroxylated toxins could be quantitated at concentrations as low as about 0.1 mug/g (10 mug/100 g). Average recoveries of the toxins through the com plete cleanup procedure were 85% or greater for spiked extracts of oysters and clams and greater than 73% for mussels.