Abstract: A portable fluorescence instrument characterized by ultraviolet excitation optics and fluorescence spectral optics, particularly adapted for analysis of oil samples. The excitation optics include circuitry that adapts the instrument for field exploration by using low voltage power obtainable either from an internal rechargeable power source or from a conventional power source or from a conventional automobile battery. The fluorescence optics include a density step tablet that modulates the fluorescence intensity resulting in a spectral display characteristic of the particular sample. The spectral display is recorded on an instant film for on-site analysis.