Liquid Chromatography Post-Column Oxidation (PCOX) Method for the Determination of Paralytic Shellfish Toxins in Mussels, Clams, Oysters, and Scallops: Collaborative Study
Authors: Van De Riet Jeffrey , Gibbs Ryan S , Muggah Patricia M , Rourke Wade A , MacNeil James D , Quilliam Michael A ,   Collaborators:, Aasen J , Amzil; B. Ben Gigirey Z , Burdaspal P , Burrell S W , Brazeau J , Carter S J , Ceredi A , Duffy C , Eaglesham G , Hatfeld R , Hillyard T , Jensen M K H , Lacaze J P , Langlois D , Legarda T M , Marcos E , Milandri A , Mulder P P J , Murphy C , Ouellette S , Panganiban C , Pante L , Paulsrud M S , Pooley B P , Reeves K , Riccardi E , Rodríguez Velasco M L , Sacrey T Z , Savar V , Selwood A , Sizoo E A , Turner A D , van Ginkel R , Wotherspoon A T L 
Published: February 2020

Abstract
Sixteen laboratories participated in a collaborative study to evaluate method performance parameters of a liquid chromatographic method of analysis for paralytic shellfsh toxins (PST) in blue mussels (Mytilus edulis), soft shell clams (Mya arenaria), sea scallops (Placopectin magellanicus), and American oysters (Crassostrea virginicus). The specifc analogs tested included saxitoxin, neosaxitoxin, gonyautoxins-1 to -5, decarbamoyl-gonyautoxins-2 and -3, decarbamoyl-saxitoxin, and N-sulfocarbamoylgonyautoxin-2 and -3. This instrumental technique has been developed as a replacement for the current AOAC biological method (AOAC Offcial MethodSM 959.08) and an alternative to the pre-column oxidation LC method (AOAC Offcial MethodSM 2005.06). The method is based on reversed-phase liquid chromatography with post-column oxidation and ﬂuorescence detection (excitation 330 nm and emission 390 nm). The shellfsh samples used in the study were prepared from the edible tissues of clams, mussels, oysters, and scallops to contain concentrations of PST representative of low, medium, and high toxicities and with varying profles of individual toxins. These concentrations are approximately equivalent to ½ maximum level (ML), ML, or 2×ML established by regulatory authorities (0.40, 0.80, and 1.60 mg STX·diHCl eq/kg, respectively). Recovery for the individual toxins ranged from 104 to 127%, and recovery of total toxin averaged 116%. Horwitz Ratio (HorRat) values for individual toxins in the materials included in the study were generally within the desired range of 0.3 to 2.0. For the estimation of total toxicity in the test materials, the reproducibility relative standard deviation ranged from 4.6 to 20%. A bridging study comparing the results from the study participants using the post-column oxidation (PCOX) method with the results obtained in the study director’s laboratory on the same test materials using the accepted reference method, the mouse bioassay (MBA; AOAC Offcial MethodSM 959.08), showed that the average ratio of results obtained from the two methods was 1.0. A good match of values was also achieved with a new certifed reference material. The results from this study demonstrated that the PCOX method is a suitable method of analysis for PST in shellfsh tissue and provides both an estimate of total toxicity, equivalent to that determined using the MBA AOAC Offcial MethodSM 959.08, and a detailed profle of the individual toxin present in the sample.