Development of an HPLC-FLD Method for Estradiol and Metabolites: Application of Solid-Phase Microextraction.

Estrogens are potent hormones involved in numerous physiological and pathological processes. Their typically low concentrations in biological samples necessitate highly sensitive analytical methods for accurate quantification. This study presents a high-performance liquid chromatography with fluorescence detection (HPLC-FLD) method for quantifying estradiol and its metabolites in blood serum and saliva. Analytes were extracted using solid-phase microextraction with a divinylbenzene sorbent and methanol as the desorption agent. FLD was performed after the derivatization of the analytes with dansyl chloride. Separation was achieved on a Poroshell 120 EC-C18 column (2.1 × 100 mm, 2.7 µm) at 50 °C using water with 0.1% formic acid and methanol as the mobile phase at 0.5 mL/min. A gradient elution increased the methanol concentration from 76% to 100% over 0-8 min, then it returned to 76% at 8.1 min and was held until 11 min had passed. Detection was at λEX 350 nm and λEM 530 nm. Good linearity was observed for estradiol, 2-hydroxyestradiol, and 2-methoxyestradiol (10-300 ng/mL; R2 = 0.9893-0.9995). The LOQ for all analytes was 10 ng/mL. Solid-phase microextraction (SPME) offered advantages over liquid-liquid extraction. The method is suitable for quantifying estrogens in the 10 ng/mL-1 µg/mL range.