Determination of 4-hydroxytamoxifen in mouse plasma in the pg/mL range by gradient capillary liquid chromatography/tandem mass spectrometry

Capillary high-performance liquid chromatography (HPLC; 300 microm i.d.) coupled to tandem mass spectrometry has been used to determine the concentration of 4-hydroxytamoxifen in mouse plasma in the pg/mL range following the administration of Tamoxifen. A limit of quantification (LOQ) of 100 pg/mL was achieved using only 25 microL of plasma. The on-column sensitivity was determined to be 100 fg. The column performance was determined isocratically before and after the assay and showed only a 15% reduction in performance after 70 injections of plasma extract. No significant peak band broadening was observed due to the mass spectrometer interface using a standard TurboIonspray source.