Determination of okadaic acid and related toxins in Greek mussels by HPLC with fluorimetric detection

The investigation for the presence of diarrhetic shellfish poisoning (DSP) toxins, okadaic acid (OA), and dinophysistoxin-1 (DTX-1), in mussels (Mytilus galloprovincialis) harvested in Thermaikos Gulf (northern Aegean Sea) is reported. The digestive glands of mussels were homogenized with methanol-water (80:20 v/v), and OA was extracted from the homogenate with hexane-chloroform (50:50 v/v). OA was reacted with 9-anthryldiazomethane (ADAM) in methanol for 1 hr at 35degreesC. The product was purified by passing through a silica solid phase extraction cartridge before being determined by reversed-phase liquid chromatography with fluorimetric detection (HPLC/FLD). Linear calibration curves (r=0.9993), in the typical analytical range of 1-10 ng OA-injected and detection limit of 0.14 ng OA-injected (S/N 3:1) were obtained. Recovery of the toxin from mussels ranged from 100.4% to 110.4%. Analysis of samples during a DSP episode in 2002 indicated the presence of OA at levels above the regulatory limit, while DTX-1 was detected in only one sample.