title: Lipophilic benzamide and anilide derivatives as high-performance liquid chromatography internal standards: application to sirolimus (rapamycin) determination.
abstract: Finding a suitable internal standard in reversed-phase high-performance liquid chromatography is often difficult. A general approach for selecting and synthesizing the proper internal standard is presented and applied to a validated method for quantitation of sirolimus in several biological matrices. A series of fifteen N-alkylbenzamides, N-alkyltoluamides and N-alkanoylanilines with a log P range of 3.51 to 6.68 were synthesized as internal standards; N-undecyl-o-toluamide was evaluated most extensively. Sirolimus quantitation involves a simple sample clean-up procedure followed by isocratic chromatography on a heated C18 analytical column with an 70% methanol-water mobile phase and ultraviolet detection at 278 nm. This method was linear from 2.5 to 200 ng with a limit of quantitation of 2.5 ng using a 1-ml blood sample. Sirolimus recovery was above 72.1%. The intra-day and inter-day coefficients of variation were less than 11.7%. Several drugs and sirolimus metabolites do not interfere with the analysis. This method was used to measure sirolimus in blood from rats, rabbits and humans.
authors.affiliation: Department of Pharmaceutics, State University of New York at Buffalo, 14260, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Ferron
authors.forename: W D
authors.initials: WD
authors.lastname: Conway
authors.forename: W J
authors.initials: WJ
authors.lastname: Jusko
mesh_terms: D000284:Administration, Oral; D000813:Anilides / Q000737:chemistry / Q000592:standards*; D000818:Animals; D001549:Benzamides / Q000737:chemistry / Q000592:standards*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002940:Circadian Rhythm; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000097:blood* / Q000737:chemistry; D007275:Injections, Intravenous; D016014:Linear Models; D011090:Polyenes / Q000008:administration & dosage / Q000097:blood* / Q000737:chemistry; D011817:Rabbits; D051381:Rats; D012015:Reference Standards; D015203:Reproducibility of Results; D020123:Sirolimus
chemical_list: D000813:Anilides; D001549:Benzamides; D007166:Immunosuppressive Agents; D011090:Polyenes; C037689:benzamide; D020123:Sirolimus