Influence of organic solvents on the fluorescence intensity of photoirradiated nicotine (A) and cotinine (B). Fluorescence intensities were normalized to organicsolvent-free conditions and plotted against the organic solvent concentration. The solvents tested were acetonitrile (open circles), methanol (open triangles), ethanol (closedtriangles), 2-propanol (open squares), and N,N-dimethylformamide (closed squares).