Automated analysis of acetaminophen and caffeine in serum using the FAST-LC system: contributions to assay imprecision in procedures based on HPLC with sample pretreatment.

Two procedures are described for the fully automated analysis of several therapeutic drugs in serum, using HPLC with on-line pretreatment (solvent extraction) of the sample. The FAST-LC system (Technicon Instruments) was used for the assay of mixtures of 1) acetaminophen, theophylline, and/or caffeine, or 2) phenylethylmalonamide, primidone, phenobarbital, carbamazepine epoxide, phenyltoin, and/or carbamazepine. The rate of sample analysis was 15/hr for the theophylline group of drugs and 12/hr for the six anticonvulsants. The precision of resulting assays was about 3% (CV), and only 75 microliter of sample was required. The precision of resulting assays, in terms of a previously reported model, is also discussed.