Validated HPLC method for the quantitative determination of CoQ(10) in dog plasma and its application to a pharmacokinetic study.

Coenzyme Q(10) (CoQ(10) ) is a naturally occurring compound located in all membranes throughout the cell. A rapid and sensitive HPLC method was developed to determine the concentration of CoQ(10) in dog plasma using a surrogate matrix. Chromatographic separation was carried out on a Diamonsil C(18) column with the UV detector set at 275 nm. Methanol-2-propanol (40:60, v/v) was used as a mobile phase delivered at a flow rate of 1.0 mL/min. Calibrators were prepared using blank plasma-K(2) HPO(4) buffer (50 mm, pH 8.0)-saline (1:3:6, v/v/v) as surrogate matrix. It was shown that the surrogate matrix had similar properties to dog plasma for CoQ(10) in extraction, freeze-thaw and stability. The assay was linear over the concentration range of 0.10-100 µg/mL. The intra- and inter-day precisions were within 13.3% in terms of relative standard deviation (RSD%) and the accuracy was within ±7.5% in terms of relative error. This simple and reproducible HPLC method with less plasma volume (0.4 mL) and adequate sensitivity was successfully applied to pharmacokinetic studies of CoQ(10) in dogs and an investigation of the effect of CoQ(10) formulation on CoQ(10) baseline levels.