Several months ago I filled out a usage survey conducted by the University of Geneva. Recently I received a follow up questionnaire which my headache is making more challenging than it should be. The question "What is the concentration of nicotine in this liquid" is asking for mg nicotine per: ml / 10ml / 100ml / litre. Considering the pre-mixed liquid many of our favorite vendors send us, can someone help me with this answer? Thanks much.