Liquid chromatographic determination of domoic acid in mussels, using AOAC paralytic shellfish poison extraction...

A liquid chromatographic method using the AOAC paralytic shellfish poison (PSP) extraction procedure for domoic acid, a marine toxin, in mussel tissue was collaboratively studied in 10 laboratories. Domoic acid is extracted by boiling the homogenized tissue for 5 min with 0.1N HCl. The mixture is cooled, diluted to a known volume, and then centrifuged. An aliquot of the supernate is diluted, filtered, and analyzed by reverse-phase liquid chromatography with a mobile phase containing acetonitrile and water adjusted to about pH 2.5. Each collaborator received a prepared standard solution, a practice sample, and 7 randomly numbered unknown samples (1 blank mussel tissue, 1 spiked at 14.1 micrograms domoic acid/g, 1 spiked at 18.9 micrograms/g, and duplicate samples with naturally incurred domoic acid at 75 micrograms/g and at 186 micrograms/g). Five of the laboratories had little or no experience in domoic acid analysis. Ten of 11 laboratories completed the study and submitted results. Two individual values out of a total of 70 were found to be outliers. Mean recovery of domoic acid from the spiked extracts was 75%. Relative standard deviations between laboratories (RSDR) ranged from 7.5 to 19.4%; within-laboratory RSDs (RSDr) for the 2 blind duplicate pairs were 1.9 and 4.8%. The detection limit was about 1 microgram domoic acid/g. The method has been adopted official first action by AOAC.