title: Optimized HPLC method for tramadol and O-desmethyl tramadol determination in human plasma.
abstract: The optimized method for HPLC determination of tramadol and its metabolite O-desmethyl tramadol in human plasma using sotalol as internal standard has been developed and validated by a new approach. The determination by fluorescence detection was performed on re-eluted solution, obtained after liquid-liquid extraction with ethyl acetate of the three analytes from plasma. The chromatographic separation of tramadol under a gradient elution was achieved at a temperature of 15 degrees C with a RP-18 column, guarded by a C18 precolumn. The mobile phase was a mixed aqueous solution containing ortho-phosphoric acid, triethylamine, acetonitrile and methanol in a complex gradient mode. The quantitative determination of tramadol was performed at different successive pairs of excitation/emission wavelengths (200/300 nm, 200/295 nm, 212/305 nm) with lower limits of quantification: LLOQ=4.078 ng/ml for tramadol, respectively LLOQ=3.271 ng/ml for O-desmethyl tramadol. For the LLOQ limits, were calculated the values of the coefficient of variation and difference between mean and the nominal concentration. For tramadol analyte they were CV%=5.147% and bias%=-7.273% in the intra-days and CV%=4.894% and bias%=0.836% in the between-days assay, respectively for the metabolite O-desmethyl tramadol they were CV%=11.517% and bias%=0.337% in the intra-days and CV%=6.41% and bias%=3.259% in the between-days assay. In addition, the stabilities of the analytes were verified in different conditions. Both, tramadol and its metabolite proved to be stable in plasma for four weeks, frozen at -20 degrees C, but also for 48 h at 15 degrees C in the re-eluted solution after liquid-liquid extraction.
authors.affiliation: University of Medicine and Pharmacy Tg-Mures, Faculty of Pharmacy, Gh. Marinescu Str. No.38, Tg-Mures RO-540139, Romania. augustin@umftgm.ro
authors.forename: Augustin
authors.initials: A
authors.lastname: Curticapean
authors.forename: Daniela
authors.initials: D
authors.lastname: Muntean
authors.forename: Manuela
authors.initials: M
authors.lastname: Curticapean
authors.forename: Maria
authors.initials: M
authors.lastname: Dogaru
authors.forename: Camil
authors.initials: C
authors.lastname: Vari
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D008745:Methylation; D015394:Molecular Structure; D015203:Reproducibility of Results; D014147:Tramadol / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D014147:Tramadol