title: Comparison of two extraction methods for determination of propranolol and furosemide in human plasma by mixed-mode chromatography.
abstract: An isocratic high performance liquid chromatographic method is described for the determination of the beta-adrenergic blocking drug, propranolol, and the diuretic, furosemide, in human plasma. The two compounds and the internal standard were extracted from plasma using a two-step extraction technique. Propranolol and pindolol (internal standard) were first extracted from alkaline plasma into diethyl ether; this was followed by extraction of furosemide into acidified ether: hexane (65:35). The two extracts were then combined and evaporated under nitrogen, and the reconstituted residues were analysed on a C18/SCX reversed-phase/cation exchange column with a mobile phase of acetonitrile: 0.1 M sodium acetate pH 4 (33:67). The drugs and the internal standard were detected by UV absorption at 230 nm. The drugs were also extracted from plasma by a column-switching technique utilizing a ten-port valve. The drug compounds were retained on a C18 pre-column. A comparison of RSD for within-batch (intra-assay) and between-batch (inter-assay) runs for both methods was carried out, the liquid/liquid extraction method giving better recovery values. The calibration graphs were linear from 25-300 ng ml-1 for furosemide and 50-400 ng ml-1 for propranolol. Recovery values were > 90.0% by liquid/liquid extraction and > 76.0% by column switching.
authors.affiliation: School of Chemical Sciences, Dublin City University, Ireland.
authors.forename: M
authors.initials: M
authors.lastname: Walshe
authors.forename: M T
authors.initials: MT
authors.lastname: Kelly
authors.forename: M R
authors.initials: MR
authors.lastname: Smyth
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000097:blood / Q000302:isolation & purification*; D002845:Chromatography / Q000379:methods; D004232:Diuretics / Q000097:blood / Q000302:isolation & purification*; D005665:Furosemide / Q000097:blood / Q000302:isolation & purification*; D006801:Humans; D010869:Pindolol / Q000097:blood / Q000302:isolation & purification*; D011433:Propranolol / Q000097:blood / Q000302:isolation & purification*
chemical_list: D000319:Adrenergic beta-Antagonists; D004232:Diuretics; D005665:Furosemide; D011433:Propranolol; D010869:Pindolol