A photoproduct of ketamine was identified in hair samples irradiated with artificial light in a solar simulator

The main advantage of hair as a testing matrix is the ability to provide information related to historical drug exposure. Indeed, hair analysis has many applications within forensic (e.g., drug-related deaths, drug-facilitated crimes (DFCs), child protection) and clinical toxicology (e.g., drug rehabilitation programs, workplace drug testing). Exposure to sunlight and/or artificial light can induce photodegradation of licit/illicit drugs through photosensitization reactions. Therefore, when decisional cut-offs are applied to hair analysis (e.g., for granting a driving license, a job, or a child custody), it must be taken into account that hair exposed to sunlight may produce false results and lead to misjudgment. To better understand the role and the mechanisms of solar light on drugs in hair, the present work aims to evaluate the photodegradation of ketamine (KET) and its metabolite norketamine (NKET) in true positive hair samples irradiated in a solar simulator. KET and NKET concentration before and after irradiation were determined by means of liquid chromatography high-resolution mass spectrometry (HPLC-HRMS) in authentic hair samples from drugs users.