Sensitive determination method of estradiol in plasma using high-performance liquid chromatography with electrochemical detection

The improvement in the sensitive determination method of estradiol using HPLC with electrochemical detection is described. The improvement was due to the optimization of the potential applied to the electrode of the analytical cell and employment of a guard cell. The detection conditions were optimized from the electrochemical properties of estradiol in acidic and alkaline eluents. The employment of the guard cell drastically decreased the background noise without any reduction in the response of estradiol, and contributed to improvement in the sensitivity. The optimized method combined with pretreatment by liquid–liquid extraction was applied to the determination of estradiol in rat plasma. The detection limit of 8 pg for the standard solution and 24 pg for the plasma sample, which was about 6–8-fold more sensitive compared to the previous reports, was attained.