RAPID HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD FOR THE DETERMINATION OF KETAMINE AND ITS METABOLITE DEHYDRONORKETAMINE IN EQUINE SERUM

A simple, rapid and sensitive high-performance liquid chromatographic procedure has been developed for the determination of ketamine and dehydronorketamine in equine serum. Sample preparation consisted of mixing equal volumes of serum and acetonitrile-phosphoric acid (85%)-water (20:2:78, v/v/v), followed by ultrafiltration through a 10 000 molecular mass cut-off filter. Separation of these two analytes in the ultrafiltrate was accomplished on a reversed-phase phenyl column eluted with methanol-acetonitrile-phosphate buffer solution. Ketamine and dehydronorketamine were detected by a variable photometric UV-Vis detector set at 215 nm, and confirmed by a photodiode array detector operated in the 200-320 nm range. The limit of detection for ketamine was 5-15 ng/ml in equine serum. Additionally, the dehydronorketamine peak identity was tentatively confirmed by thermospray liquid chromatography-mass spectrometry.