Small-Volume Voltammetric Detection of 4-Aminophenol with Interdigitated Array Electrodes and Its Application to Electrochemical Enzyme Immunoassay

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Analytical Chemistry


A small-volume voltametric detection of 4-aminophenol (PAP) has been developed using an interdigitated array (IDA) microelectrode cell in order to apply the IDA to electrochemical enzyme immunoassay. The signal of PAP at the IDA was steady state, and its magnitude was amplified compared with that of the usual single electrode due to redox cycling of PAP between the two finger sets of the IDA. A linear relationship between PAP concentration and cathodic limiting current was obtained from 1 to 1000 μM, reproducibly. The minimum sample volume in the measurement was reduced to 800 nL. High sample throughout of less than 1-min detection time per sample was achieved on 2-10 μL PAP samples. This IDA cell was applied to the electrochemical enzyme immunoassay of mouse IgG. Alkaline phosphatase was used as the enzyme label. The mouse IgG concentration was evaluated by detecting the concentration of PAP, which is the product of enzymatic reaction of the substrate, 4-aminophenyl phosphate (PAPP). Anti-mouse IgG was covalently immobilized on the glass surface of the small-volume immunowells by carbodiimide coupling. The assay range was 10-1000 ng/mL using 10- μL sample and 20- μL substrate solutions.