Sulfonium salts as derivatizing agents

An automated gas chromatographic method for determination of theophylline in plasma is described. A novel feature of this assay is the use of triethylsulfonium hydroxide as an on-column alkylating agent. A simple extraction procedure together with automated sample injection and data processing has facilitated processing of large numbers of samples generated in pharmacokinetic studies. The between-run coefficient of variation was 2.2% at 5 micrograms/ml (n = 5) and 3.9% at 15 micrograms/ml (n = 6). Within-run coefficient of variation was 2.4% at 5 micrograms/ml (n = 9) and 3.3% at 15 micrograms/ml (n = 6). Accuracy was 105% at a concentration of 5 micrograms/ml and 102% at 15 micrograms/ml.