Analysis of gamma-(cholesteryloxy)butyric acid in biologic samples by derivatization with 5-(bromomethyl)fluorescein followed by high-performance liquid chromatography with laser-induced fluorescence detection.

This report describes the first application of 5-(bromo-methyl)fluorescein (5-BMF) for the quantitation of a pharmaceutically relevant carboxyl-containing analyte in a biological matrix. An analytical method for quantitation of gamma-(cholesteryloxy)butyric acid (CBA), a relatively new antitumor agent, in different tissues of Sprague-Dawley rats was developed. 5-BMF was employed to form a stable and spectrally well-characterized conjugate of CBA. The derivatization yield was maximized by optimizing several reaction variables. The conjugate was separated by high-performance liquid chromatography and quantitated by a laboratory-constructed argon ion laser fluorometer. The detection limits for CBA were 4.6 x 10(-9) and 6.34 x 10(-11) M by conventional and laser-induced fluorescence (LIF), respectively. A derivatization limit of detection of 1.85 x 10(-9) M was achieved by LIF for the conjugate The analytical method was useful for quantitation of CBA in various tissues in the picogram per milliliter range.