Abstract: A method for the simultaneous determination of okadaic acid (OA) and its derivatives dinophysistoxin-1 (DTX-1), pectenotoxin-2 (PTX-2)and yesstoxin (YTX) in shellfish using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. After being extracted with methanol, the extract was cleaned-up by solid phase extraction of a StrataTM-X cartridge. The separation of the 4 toxins were performed on a XTerra MS C18 column (100 mm×2.1 mm, 3.5 μm) using gradient elution of acetonitrile and water both containing ammonium formate and formic acid as eluent modifiers. The qualitative and quantitative analysis were carried out by electrospray ionization (ESI) mass spectrometry in selective reaction monitoring (SRM) mode. The OA, DTX-1 and YTX were analyzed in negative ion mode, while PTX-2 in positive ion mode. The matrix-matched external standard calibration curves were used for the quantitative analysis. The calibration curves were linear in the range of 2.0~200.0 μg/L for OA, DTX-1 and YTX, 1.0~100.0 μg/L for PTX-2, with the quantification limits of 1.0 μg/kg and 0.5 μg/kg, respectively. The average recoveries for the toxins were between 83.1%and 105.7% with the relative standard deviations (RSD) of 3.16%~9.29%. The proposed method is sensitive, effective and simple. It was applicable for the determination and confirmation of OA, DTX-1, PTX-2 and YTX in shellfish products. The OA, DTX-1, PTX-2 and YTX in some shellfish samples collected from Yellow Sea were found by the method.

Key words: dinophysistoxin, okadaic acid, pectenotoxin, shellfish, yessotoxin, liquid chromatography-tandem mass spectrometry (LC-MS/MS)