Patent ID: 7161145

Claim:
An apparatus for identifying analytes at low concentration in a liquid sample comprising a solvent and said analytes by mass spectrometry comprising: a zone of ionization for ionizing gaseous or liquid analytes; a membrane impermeable to solvent and permeable to at least a portion of the amount of said analytes contained in said liquid sample, whereby said permeable analytes are deliverable to said zone of ionization; a capillary tube adapted for receiving the portion of said liquid sample impermeable to said membrane containing other analytes not retained on said membrane, said tube directed to introduce said liquid sample and other analytes from said membrane to said zone of ionization; a first source for providing radiation for performing resonance enhanced multiphoton ionization of said analytes; a second source for providing radiation for performing single photon ionization of said analytes; a system of reflecting surfaces for selectively directing radiation either from said first source or said second source to said zone of ionization; and a mass spectrometer for determining the m/e ratio of ions formed in said zone.