LC-UV and LC-MS methods for the determination of domoic acid

Abstract

Under European legislation, domoic acid (DA), the main constituent of amnesic shellfish poisoning, is monitored to protect the shellfish consumer. To ensure comparability amongst analytical data, it was deemed necessary to undertake performance assessments of the methods conducted by monitoring laboratories of the United Kingdom and Ireland. In phase I of a two-phase inter-comparison, three laboratories used high-performance liquid chromatography and ultraviolet detection (HPLC-UV). Concentration data for a DA standard solution, a crude extract of whole scallops and a scallop-homogenate fell within internationally accepted limits, demonstrating good agreement for these matrices. Between-laboratory analyses of a scallop gonad showed a higher variation (>16%). In phase II, a second gonad homogenate containing DA one order of magnitude higher in concentration gave results acceptable to internationally set criteria. The efficiency of the strong anion-exchange cartridges used in sample-extract clean-up should be monitored as part of a laboratory quality control system. From a recovery study, it is suggested that recovery correction should also be applied. There was no difference in the quantitation of DA in standard solutions or shellfish using either LC-UV or LC with mass spectrometric (MS) detection, and between-laboratory MS data for a gonad homogenate were also equivalent. Variations of the published method practised by the monitoring laboratories were found not to compromise results, thus demonstrating an acceptable degree of ruggedness, as well as comparability between the participants.