Liquid chromatography/tandem triple-quadrupole mass spectrometry for determination of paclitaxel in rat tissues

A liquid chromatography/tandem triple-quadrupole mass spectrometry assay to quantify paclitaxel in rat tissue homogenates containing taxol or paclitaxel nanoliposome (PTX-NLP) was developed and validated. Liquid-liquid extraction with tert-butyl methyl ether was used for tissue sample preparation and docetaxel was used as the internal standard. Paclitaxel and docetaxel were separated on a 200 mm x 4.6 mm x 5 microm C(18) column and quantified using a triple-quadrupole mass spectrometer operating in positive ion electrospray selective reaction monitoring mode (ESI(+)-SRM) with a total run time of 6.0 min. The peak area of the m/z 876.3 --> 307.9 transition of paclitaxel is measured versus that of the m/z 830.3 --> 549.1 transition of docetaxel to generate the standard curves. The standard curves were linear over the concentration range of 0.2008-2008 ng/mL for different tissues. The method had high extraction recovery (>90%) and accuracy (>90%) with the intra-day and inter-day precision <15%. Frozen stability, freeze/thaw stability, extraction stability and solution stability at ambient temperature were examined, which indicated the tissue samples should be extracted within 5 days and avoid being frozen and thawed repeatedly over 5 times. Extracted samples after evaporation could be stored at -20 degrees C for 20 days without drug degradation and no degradation was also observed after solution samples were left to stand at ambient temperature for 24 h. This assay was used to support an in vivo biodistribution study of PTX-NLP in rats.