Abstract: There is provided a method for determining the level of a polycyclic compound of interest present on the surface of a tobacco leaf, the method comprising the steps of: (a) washing the surface of the tobacco leaf with a solvent, the solvent comprising at least a non-polar solvent, such that no greater than about 10 wt. % of the polycyclic compound of interest present on the surface of the tobacco leaf is removed from the surface of the tobacco leaf; (b) collecting the solvent from step (a); and (c) subjecting the collected solvent to fluorescence spectroscopy to determine the level of the polycyclic compound of interest.