Adaptation of microvolume EMIT assays for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin to a CentrifiChem chemistry analyzer.

We have developed microvolume EMIT procedures for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin using a centrifugal analyzer (CentrifiChem and Pipettor 1000) to reduce the manufacturer's recommended manual reagent consumption by one-sixth. In addition to developing the EMIT procedure, the performance of the analyzer and pipettor were verified. The analyzer and pipettor are capable of producing within-run precision at a 3-microliters sample volume and 210-microliters analyzer cuvette volume equal to or less than 1.5%. The performance of the EMIT procedures on the analyzer yielded spike drug recoveries of 90.8 to 106.1% for drug concentrations throughout the calibration concentration range of each assay. The percent error on standard reference material of the National Bureau of Standards ranged from a +12.0% to a -0.6% for ethosuximide, phenobarbital, phenytoin, and primidone. Patient comparison data yielded slopes from 0.930 to 1.110 for all assays. The other important feature of the adapted EMIT assay is its simplicity for use on a routine basis.