| abstract |
Described is a method and apparatus for analyzing an organic sample. In the preferred embodiment, this method and apparatus allows the determination of the base sequence of a nucleic acid by determining the molecular weights of the components of a biological sample. The method uses either a pre-existing chromophore or the covalent attachment of an ionizable chromophore to a biological sample followed by the vaporization of these molecules by exposure to an intense pulse of electromagnetic radiation (14) in the presence of a matrix which strongly absorbs the radiation. The gaseous molecules are subsequently extracted into an evacuated ionization chamber (15) and then exposed to electromagnetic radiation (32) at a wavelength which specifically excites the chromophore covalently attached to the biological sample. |