Trace determination of 1-octacosanol in rat plasma by solid-phase extraction with Tenax GC and capillary gas chromatography.

1-Octacosanol is the major component of policosanol, a new natural lowering-cholesterol agent. A sensitive solid-phase extraction with a Tenax GC capillary gas chromatography method for determining the proportion of this fatty alcohol in plasma after its denaturation with trichloroacetic acid was developed. The trimethylsilyl ether derivative of the target analyte obtained from the organic extract showed excellent chromatographic properties and was detectable in the low nanogram range (1 ng/ml). Adequate separation from plasma's extract was achieved with a fused-silica capillary column (30m x 0.25 mm I.D.) with SPB-5 (0.5 microm film thickness) and operated with temperature programming from 100 to 200 degrees C at 40 degrees C/min and from 200 degrees C increased at 10 degrees C/min to 320 degrees C, then held for 30 min, the carrier gas flow-rate (argon) was 1 ml/min. Quantification was performed by the internal standard method using 1-hexacosanol. The reliable relative retention parameters and the mass response factors values, and their confidence levels, ensure a proper GC sensitivity, necessary for the determination of the alcohol being analyzed. The method was evaluated to a concentration range from 6 to 47.6 ng/ml of plasma obtaining recoveries from 95 to 98%. The correlation between the theoretical concentration values and the corresponding experimental values was appropriate (gamma=0.9718 x -0.0915; r2=0.9998). The method showed a good within-day (RSD=4.3%) and between-day (RSD=6.0%) precision according to the acceptance criteria (<10%). This procedure was successfully applied to the study of 1-octacosanol in rat plasma samples after a single oral administration (40 mg/kg) of policosanol.