New Psychoactive Substances (NPS) is an umbrella term covering hundreds of substances across different drug groups. Many of these substances were originally developed for therapeutic use but have later appeared on the recreational drug market. The use of NPS has been associated with many outbreaks leading to hospitalizations and has been implicated in numerous fatalities worldwide. To be able to analytically detect drugs in a forensic setting is vital in the fight against the abuse of NPS. One of the most notable challenges in detection of NPS is the identification of major urinary metabolites for use as biomarkers. Furthermore, given the lack of reference standards in most metabolism studies, the major urinary metabolites can often only be tentatively determined. Docent Johan Dahlén, my main supervisor, for allowing me the opportunity to carry out my research as a PhD student. Thank you for your positive attitude, support, encouragement and for your ability to turn problems into opportunities. Professor Peter Konradsson, my co-supervisor, for accepting me as a PhD student and for encouraging me to strive forward. Thank you for your guidance in chemistry as well as for your enjoyable music and sports analogies. Doctor Xiongyu Wu, my co-supervisor, for being an exceptional person and a master chemist. Thank you for always being there for me when I needed support or advice, never making me feel like a nuisance. You will always have my utmost admiration and appreciation. The people currently or previously working at the National Board of Forensic Medicine, Svante, Martin, Henrik, Anna, Robert, Ariane and Shimpei for excellent collaboration. Thank you for letting me partake in your fascinating research, it was the highlight of my time as a PhD student. Katriann Arja, for being a truly genuine and caring friend as well as an excellent life coach. Thank you for being a beacon of positivity and for lifting the spirits of everyone around you. Lastly, for our running sessions and discussions about happiness, Aitäh! Linda Lantz, my big sister at work, for taking me under your wing and making me feel at home. Thank you for trying to teach me everything from how to speak to how to run. Very few things make me as happy as baking pastries and treating you to them. Marcus Bäck, my brother from another mother, for your perpetual support, encouragement and most enjoyable company. Few people can relate to or understand me on a personal level as well as you can. VI Mathias Elgland, my doppelganger, for sharing all my peculiar interests. I have thoroughly enjoyed all our time together, from listening to Ludde to throwing flat circular objects around and everything in between. Anders Rexander, my former brother in arms, for all the enjoyable banter and hard-fought duels in various racket sports. The lab was never the same without you. Caroline Eriksson, my dear friend, for helping me break out of my shell. Few people have had such a positive impact on me as a person as you have. Tobias Abrahamsson for being around since the beginning...