Analysis of etorphine in postmortem samples by HPLC with UV diode-array detection

Etorphine is a synthetic narcotic analgesic usually used in veterinary medicine. It possesses an analgesic potency up to 1000 times greater than morphine and is therefore used in low doses, primarily for tranquilising large animals. For veterinary use, etorphine is usually available in its commercial formulation as Immobilon, when in combination with acepromazine or methotrimeprazine. Due to the potency of etorphine, only very low doses are required to produce adverse or fatal effects. This paper describes a method for detecting and quantifying etorphine using HPLC with UV diode array detection (HPLC-DAD) and demonstrates the advantage of the technique for the detection of Immobilon at low doses. In a forensic case involving Immobilon, the etorphine concentrations measured in postmortem femoral vein and heart blood specimens were 14.5 and 23.5 micrograms/l, respectively. No etorphine was detected in the urine. To our knowledge this is the first time postmortem etorphine concentrations have been reported.