Hair testing of propofol by liquid chromatography-tandem mass spectrometry and azo-coupling derivatization

Propofol is a short-acting intravenous hypnotic-amnesiac agent used in the general anesthesia. In recent years propofol has gained importance for recreational use (being able to give euphoria, relaxation, sexual hallucinations and disinhibition) and for suicidal purposes. For these reasons, forensic toxicology interest in this substance has increased as well, taking into account the chance of its detection in hair. In this study, a new method in liquid chromatography-tandem mass spectrometry for hair detection of propofol was applied in two real cases for clinical and forensic purposes. This method consists in propofol derivatization with a diazonium salt from aniline and a liquid-liquid extraction with dichloromethane and ethyl acetate. Lower limit of quantification in negative ionization mode is 0.1 pg/mg. In Case 1, a segmental analysis was carried out on a sample collected from a female declaring self-administration. Propofol was found in the second and third segment at concentration of 0.21 and 0.11 ng/mg. In case 2, propofol was detected at 0.50 ng/mg in pubic hair from a male underwent a gastroscopy. In this study we validated and successfully applied a new versatile, sensitive and efficient method for hair detection of propofol even after a single administration.