title: Bioanalysis of tobramycin for therapeutic drug monitoring by solid-phase extraction and capillary zone electrophoresis.
abstract: A method based on solid-phase extraction (SPE) and capillary zone electrophoresis (CZE) for the analysis of tobramycin in human serum is presented. An off-line SPE employing a carboxypropyl bonded phase (CBA) cartridge was used for the extraction of tobramycin from human serum. Adsorbed tobramycin was eluted from the CBA cartridge using a mixture of NH(3) (25%, w/v)-methanol (30:70, v/v). After evaporation, the analyte was reconstituted and derivatized with o-phthaldialdehyde (OPA)/3-mercaptopropionic acid (MPA). The resulting tobramycin-OPA/MPA derivative was purified, and then identified by mass spectrometry. The tobramycin-OPA/MPA derivative was then analysed by CZE with a background electrolyte (BGE) comprising of 30 mM sodium tetraborate pH 10.0-acetonitrile (ACN) (80:20, v/v) with ultraviolet detection at 230 nm. A linear response was observed in the range of 0.3-30 microg/ml with r(2) = 0.992. The sensitivity of the method was determined by its limit of quantitation (LOQ) and limit of detection (LOD) of 0.3 microg/ml and 0.1 microg/ml, respectively. SPE recovery ranged from 68 to 79% at the trough levels to 98% at the peak levels found in serum. Furosemide has been added as internal standard (IS) to improve precision. For the therapeutic range of tobramycin in serum (2-10 microg/ml) the relative standard deviation (R.S.D.) was less than 11% for the entire SPE/CE process. The method demonstrated excellent selectivity as shown by the lack of interference from a total of 20 drugs investigated. The method was then used in therapeutic drug monitoring of patients receiving the drug.
authors.affiliation: Laboratory of Pharmaceutical Chemistry and Drug Analysis, K.U. Leuven, E. Van Evenstraat 4, B-3000 Leuven, Belgium.
authors.forename: Humphrey
authors.initials: H
authors.lastname: Fonge
authors.forename: Eliangiringa
authors.initials: E
authors.lastname: Kaale
authors.forename: Cindy
authors.initials: C
authors.lastname: Govaerts
authors.forename: Koenraad
authors.initials: K
authors.lastname: Desmet
authors.forename: Ann
authors.initials: A
authors.lastname: Van Schepdael
authors.forename: Jos
authors.initials: J
authors.lastname: Hoogmartens
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000097:blood / Q000493:pharmacokinetics; D016903:Drug Monitoring; D019075:Electrophoresis, Capillary; D006801:Humans; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D012015:Reference Standards; D015203:Reproducibility of Results; D014031:Tobramycin / Q000032:analysis* / Q000097:blood / Q000493:pharmacokinetics
chemical_list: D000900:Anti-Bacterial Agents; D007202:Indicators and Reagents; D014031:Tobramycin