2.2. Biological samples
For the method validation, blood and urine samples collected in vivo were obtained from forensic examinations performed in the forensic clinical service of the centre branch of the Portuguese National Institute of Legal Medicine and Forensic Sciences in Coimbra in accordance with the Portuguese road traffic law. The post-mortem samples (blood, urine and vitreous humor) were collected from autopsies performed in the forensic pathology service of that institution or in the Medico-Legal Offices from central regions of Portugal. These samples were free of VOCs, as they were screened before being studied. All samples were stored at -20 *C until analysis.