Highly Sensitive Analysis by Laser Multi-Photon Ionization Spectrometry

Abstract

A highly sensitive detection of photoabsorbing molecules can be carried out by the laser multi-photon ionization method combined with the conductivity measurement. Photoionization mechanism has been investigated by irradiating a laser beam on photoabsorbing molecules in solution and on surface. The photoionization current is due to the motions of electrons, cations and anions, and their time profiles are subject to a space charge effect. The analytical procedure has been optimized on the basis of the investigations on mechanism. Typical detection limits are the following: pyrene in hydrocarbon solvents was 6 ppt, pyrene in water was 9 ppt, and BBQ on a platinum surface was below 1 % of monolayer coverage. This method can be applied to a highly sensitive HPLC detector. These results indicate that the laser multi-photon ionization is a sensitive and useful analytical technique. © 1993, The Japan Society for Analytical Chemistry. All rights reserved.