Fast method for simultaneous quantification of tamoxifen and metabolites in dried blood spots using an entry level LC-MS/MS system.

The purpose of this study was to develop and validate a new liquid chromatography-tandem mass spectrometric (LC-MSMS) assay for the simultaneous quantification of tamoxifen (TAM) and its main therapeutically active metabolites, N-desmethyltamoxifen (NDT), 4-hydroxytamoxifen (4HT) and endoxifen (END) in dried blood spots. Ultrasound assisted methanolic extraction was used for TAM and metabolites extraction from dried blood spot. After evaporation and methanol reconstitution, the extract was injected into a LC-MSMS system. Reversed phase chromatography was performed on a C18 grafted column in gradient mode. TAM, metabolites, and internal standard (diazepam-d5; IS) were identified in positive electrospray ionization mode using m/z transition of 372.5>72.1 (TAM); 374.23>58.10 (END); 358.27>58.10 (NDT); 388.23>44.80 (4HT) and 290.00>198.00 (IS). Total analytical run time was 6.5min. Assay was linear from 1 to 500ng/mL for all substances and presented intra and inter-assay precision and accuracy