title: Development and validation of a solid-phase extraction-liquid chromatographic method for determination of amoxicillin in plasma.
abstract: A bioanalytic method for the determination of amoxicillin in plasma by hydrophilic interaction solid-phase extraction and liquid chromatography has been developed and validated. Plasma was precipitated with acetonitrile before samples were loaded onto a zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) solid-phase extraction column. Amoxicillin was analyzed by liquid chromatography on an Aquasil (150 x 4.6 mm) LC column with mobile-phase acetonitrile: phosphate buffer (pH 2.5; 0.1 mol/L) (7:93, v/v) and UV detection at 230 nm. A regression model using 1/concentration weighting was found the most appropriate for quantification. The intraassay precision for plasma was 3.3% at 15.0 microg/mL and 10.9% at 0.200 microg/mL. The interassay precision for plasma was 1.8% at 15.0 microg/mL and 7.5% at 0.200 microg/mL. The total-assay precision for plasma over 4 days using a total of 20 replicates was 13.2%, 5.5%, and 3.8% at 0.200 microg/mL, 3.00 microg/mL, and 15.0 microg/mL, respectively. The lower limit of quantification and the limit of detection were 0.050 microg/mL and 0.025 microg/mL, respectively, for 100 microL plasma. Long-term storage stability studies of amoxicillin in plasma indicate that a temperature of -80 degrees C is necessary to prevent degradation of amoxicillin.
authors.affiliation: Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand. niklas@tropmedres.ac
authors.forename: N
authors.initials: N
authors.lastname: Lindegårdh
authors.forename: T
authors.initials: T
authors.lastname: Singtoroj
authors.forename: A
authors.initials: A
authors.lastname: Annerberg
authors.forename: N J
authors.initials: NJ
authors.lastname: White
authors.forename: N P J
authors.initials: NP
authors.lastname: Day
mesh_terms: D000658:Amoxicillin / Q000097:blood* / Q000302:isolation & purification / Q000592:standards; D002138:Calibration; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D016903:Drug Monitoring / Q000379:methods; D004355:Drug Stability; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D000658:Amoxicillin