ANALYSIS OF DOMOIC ACID AND ISOMERS IN SEAFOOD BY CAPILLARY ELECTROPHORESIS

Methods for the analysis of domoic acid (DA) based upon capillary elec trophoresis (CE) combined with UV absorbance detection were investigat ed. DA could be analyzed using bare fused-silica capillaries in either the cationic or anionic mode with acidic or basic buffer systems, res pectively. Highest performance, in terms of both separation efficiency and analysis time, was achieved with phosphate or berate buffers at a pH of approximately 9. The addition of beta-cyclodextrin to the berat e buffer permitted a separation of DA and several of its isomers (isod omoic acids) that was superior to that achieved with liquid chromatogr aphy (LC). The optimum background electrolyte for the separation was 2 2.5 mM sodium tetraborate at pH 9.2 with 20 mM beta-cyclodextrin. In a ddition, an extraction and clean-up procedure was developed and tested with mussels, clams and anchovies. Aqueous methanol extraction of sam ples followed by a tandem strong anion and strong cation exchange clea nup provided an extract that was completely compatible with CE analysi s. A mass detection limit of 3 pg of DA injected and a method detectio n limit of 150 ng/g in tissues could be achieved. Comparison with LC s howed that comparable precision and accuracy could be attained by the two techniques.