Small volume bead assay for ovalbumin with electrochemical detection

A bead based sandwich enzyme immunoassay coupled to electrochemical detecti on for ovalbumin has been developed. The enzyme label alkaline phosphatase was used to convert the substrate 4-aminophenyl phosphate to electroactive product 4-aminophenol. The detection was done in a microdrop by continuousl y monitoring the enzyme turnover with a rotating disk electrode. This reduc es dilution of the enzyme product, a key to achieving low detection limits. The assay developed has a detection limit of 0.1 ng ml(-1). Assay sensitiv ity in complex matrices such as food and serum was compared.