Paralytic Shellfish Toxins

By: Saji George

The paralytic shellfish toxins (PSTS) are a group of secondary metabolites (biotoxins) deposited in bivalve shellfish by dinoflagelates. Dinoflagelates blooms are seasonal, occurring during warm months. Since it is unpredictable whether an infestation will occur, the shellfish population should be regularly monitored for toxins. Ingestion of contaminated shellfish can lead to paralytic shellfish poisoning; a life-threatening illness.

Mouse bioassay (MBA) was the official method of AOAC International, but the drawbacks associated with this method have led to exploration of chemical methods. The most common HPLC post-column method is to oxidize the separated toxins under alkaline conditions to a fluorescent compound. Sullivan et al. used this method to determine the gonyautoxins 1-6 (GTX1-6), saxitoxin (STX) and neosaxitoxin (neoSTX) but not the N-sulfocarbamoyl-11-hydroxysulfate toxins (C1-C4). Oshima et al. modified this method to determine the 3 toxin groups separately using isocratic elution with 3 different mobile phases. An improved method using post-column oxidation (PCOX) followed by fluorescence detection was developed by Canadian Food inspection Agency (CFIA) in collaboration with National Research Council Canada (CNRC) has led to a shorter analysis time to determine the 3 groups of toxins using step gradient and a switching valve.

This method offers a high throughput alternative to live animal testing or lengthy instrumental methods currently acceptable for regulatory testing. All MBA analyses for PSTs were eliminated in CFIA laboratories when the PCOX method was granted Official Method of Analysis (OMA), First Action status in April, 2011, and the PCOX method was considered a quantitative, regulatory method, without the need for MBA confirmation of results. The PCOX method was promoted to AOAC OMA 2011.02, Final Action status in 2013.

For further reading/information here’s a very helpful link to a video from one of our customers, The Sitka Tribe of Alaska , which does a great job walking through the collection/testing process.  If you are interested, Pickering Labs has created our own PSP method utilizing our Post-Column instrumentation.