Adaptation of "EMIT" technique for serum phenobarbital and diphenylhydantoin assays to the miniature centrifugal analyzer.

We used a miniature centrifugal analyzer in a spectrophotometric rate-measurement mode to determine the anticonvulsant drugs phenobarbital and diphenylhydantoin in serum, by use of a modified enzyme immunoassay ("EMIT", Syva Corp.) We decreased reagent cost per determination by at least sixfold by means of microscale techniques. Also, the analysis rate is increased by measuring multiple samples simultaneously. Our method requires only 3 mul of serum for duplicate determinations. Replicate analyses of sera containing phenobarbital and diphenylhydantoin gave reaction rates with a CV of 1.5%. Run-to-run CV was 15%. Analytical recovery for drug-supplemented serum samples was 98%, and results for a series of samples compared well with results obtained by gas chromatography (for phenobarbital, r = 0.95; for diphenylhydantoin, r = 0.91).