Quantification of domoic acid in shellfish samples by capillary electrophoresis-based enzyme immunoassay with electrochemical detection.

A new method was developed to quantify domoic acid by capillary electrophoresis-based enzyme immunoassay (CE-EIA) with electrochemical (EC) detection. The method was based on noncompetitive immunoreaction between free domoic acid antigen (Ag) and excessive amount of horseradish peroxidase (HRP)-labeled antidomoic acid antibody tracer (Ab*) in liquid phase. Then the bound enzyme-labeled complex (Ab*-Ag) and unbound Ab* were separated by CE, and the system of HRP catalyzing H(2)O(2)/o-aminophenol (OAP) reaction was adopted for EC detection. Using CE-EIA with EC detection, equilibrium was reached in 30 min, and the analytical results were obtained within a further 5 min. The linear range and the detection limit were 0.1-50 ng/mL and 0.02 ng/mL, respectively. Analytes recoveries were 89.6-105.8%. The sensitivity of the method was 16 times greater than that of enzyme-linked immunosorbent assay (ELISA). The developed method was applied to quantitatively analysis of domoic acid in contaminated shellfish samples with rapid and simple pretreatment, and the results were consistent with the same samples analyzed through ELISA. The CE-EIA with EC detection provides a valid and sensitive analytical approach, not previously available, for determination of domoic acid in shellfish samples.