Determination of yohimbine in serum by high performance liquid chromatography

An automated method for determination of yohimbine (Yoh) in the serum was developed by means of column switching high performance liquid chromatography (HPLC). TSK-precolumn BSA-ODS and TSK-gel ODS-120T were used as a precolumn and analytical column, respectively. The wavelengths of detection were used at 280 nm (excitation) and 360 nm (emission). A 100 microliter serum sample is directly injected onto the precolumn. Yoh is then eluted within 30 min with an methanol-potassium phosphate buffer mixture. The analytical recoveries (99.3-110.4%), reproducibilities (within-run, C.V. less than 2.27%), and detection limit (0.80 ng/ml, S/N = 3) indicate that this system is suited for determination of Yoh. The five healthy volunteers received a single oral dose 10 mg of HYoh powder. The average of the maximal serum concentration and the area under the curve (AUC) from 0 to 4 h were 10.3 +/- 0.88 ng/ml and 19.70 +/- 0.87 ng.h.ml-1, respectively. The elimination rate constant (Kc1) was 0.52 +/- 0.03 h, and biological half-life (t1/2el) was 1.32 +/- 0.12 h.