title: High-performance liquid chromatography using on-line solid-phase extraction: determination of furosemide in human serum.
abstract: An on-line solid-phase extraction technique based on column switching (heart-cutting) was developed for direct injection analysis of furosemide in human serum. In order to minimize the influence of deterioration in pre-treatment column efficiency, which was caused by protein precipitation with repeated injections of serum, furosemide was completely enriched at the top of the analytical column by ion-pair formation with tetra-n-butylammonium ion during heart-cutting. The robustness of the established on-line solid-phase extraction system was confirmed under routine conditions. As a result, almost comparable chromatograms could be obtained even though 50 repeated injections of a 100-microliter volume of serum were carried out using one pre-treatment column. The linearity of the calibration curves was demonstrated by the correlation coefficient which was greater than 0.99999 (5-1000 ng/ml). The relative errors and C.V. of quality control samples were within 4.00 and 5.88%, respectively (furosemide concentrations: 5, 100 and 1000 ng/ml).
authors.affiliation: Drug Analysis and Pharmacokinetics Research Laboratories, Takeda Chemical Industries, Ltd., Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Okuda
authors.forename: K
authors.initials: K
authors.lastname: Yamashita
authors.forename: M
authors.initials: M
authors.lastname: Motohashi
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004232:Diuretics / Q000097:blood*; D005665:Furosemide / Q000097:blood*; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D004232:Diuretics; D005665:Furosemide