title: The liquid chromatographic determination of theophylline in untreated plasma by simple direct injection.
abstract: A liquid chromatographic method for determination of theophylline by direct injection of untreated plasma samples is described. Theophylline is detected without interference from related compounds such as paraxanthine. A precolumn venting technique is used which considerably increases column life. The lifetimes of the separation columns are unaffected by plasma injections whereas the precolumn has to be changed after 140 injections (10 mul of plasma). The peak purity of theophylline is examined spectrophotometrically. Determinations are performed by external standardization with recoveries close to 100% with a precision better than 2.3% (RSD).
authors.affiliation: Department of Analytical Pharmaceutical Chemistry, Biomedical Center, University of Uppsala, Box 574, S-751 23 Uppsala, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Daoud
authors.forename: T
authors.initials: T
authors.lastname: Arvidsson
authors.forename: K G
authors.initials: KG
authors.lastname: Wahlund