Capillary electrochemical enzyme immunoassay (CEEI) for phenobarbital in serum

A competitive heterogeneous capillary enzyme immunoassay with electrochemic al detection has been developed for phenobarbital in serum. The oxidized pr imary antibody was attached covalently to the modified interior surface of a microcapillary (22 mu l). The competition between analyte phenobarbital a nd alkaline phosphatase labeled phenobarbital for a limited number of antib ody binding sites was complete in 1.5 h. The enzymatic product (p-aminophen ol) from the catalytic conversion of the substrate (p-aminophenyl phosphate ) was detected by amperometric flow injection analysis. The calibration cur ve for phenobarbital had a detection limit of 30 mu g l(-1) (2.8 pmoles or 0.65 ng) and a range of 30-3000 mu g l(-1). The assay could be used to dete rmine the phenobarbital serum concentration in a 4 mu l clinical serum samp le without pretreatment. (C) 1999 Elsevier Science B.V. All rights reserved .