The determination of raloxifene in rat tissue using HPLC.

We report a rapid and reliable HPLC-UV method for determination of raloxifene, a kind of selective estrogen receptor modulator (SERM), in rat tissue. Proteins were precipitated by adding 200 microL of acetonitrile and 50 microL of methanol to 100 microL of the tissue homogenates, following vortex mixing and centrifugation. Separation was carried out on a reversed-phase C(18) column (150 x 4.6 mm, 5 microm) with a mobile phase of acetonitrile:0.05 m ammonium acetate (pH 4.0 +/- 0.1; 33:67, v/v) at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 289 nm and the temperature of column was kept at 23 degrees C, without interference from endogenous tissue compounds. The calibration curve was linear from 0.0125 to 10.0 microg/mL with correlation coefficient of over 0.994, while the limit of quantification was 0.008 microg/mL. The intra- and inter-day coefficients of variation were less than 10% (RSD). The recovery of assay was between 95.8 and 104.5%. Furthermore, the method was used to measure the concentration of raloxifene in rat tissue after a simple oral dose. The highest level was observed in liver, lung, spleen, then heart and kidney. The lowest level was found in brain. These results suggest that raloxifene distributes rapidly and moderately into tissues such as liver, lung and spleen.