Determination of the docetaxel vehicle, polysorbate 80, in patient samples by liquid chromatography–tandem mass spectrometry

A new simple method was developed for the quantitative determination of the docetaxel (Taxotere) vehicle, polysorbate 80 (Tween 80), in human plasma. Calibration curves were constructed in the range of 1–100 μg/ml, using paclitaxel (0.01 mM) as internal standard, and were analyzed using a power fit with equal weighting. Sample pretreatment involved a one-step extraction with acetonitrile–n-butyl chloride (1:4, v/v). The analytes were separated on a Waters X-Terra MS column (50×2.1 mm I.D.) packed with 3.5-μm ODS material, and eluted with methanol–water (9:1, v/v) containing 0.1% formic acid. The column effluent was monitored by tandem mass spectrometry with electrospray ionization. The overall extraction efficiency was 50–60%, with values for precision and accuracy of ≤16% and <15% relative error, respectively. Our current method is ∼60–100-fold more sensitive than previous assays, and will be used to define Tween 80 disposition in patients receiving Taxotere.