A validated single-step saliva and serum sample extraction LC-MS/MS method for the analysis of nicotine, cotinine and 3'-hydroxycotinine for clinical vaping studies. - van der Velpen V; Liakoni E; Hirt MB; Vonwyl CM; Christen SE; Duthaler U; Jacob P; Haschke M (Journal of pharmaceutical and biomedical analysis, 2025)