RESUMO
The technique of laser-induced atomic-ionization (AI) in flames has been used for direct determination of Na, K, Rb, and Cs in samples such as water, high-purity alkali metals and their salts and polymeric organosilicon compounds. Different procedures for sample introduction into the flame were studied: (a) the sample was placed onto the cathode of the detector (this gave limits of detection for Na and Cs of 4 x 10(-16) and 2 x 10(-15) g, respectively), (b) electrothermal vaporization and (c) aspiration of the sample into the flame. To reduce the interference of SiO(2) in the AI determination of K in polymeric organosilicon compounds (at the level of 10(-3)-10(-5)%), a procedure involved additional electrical heating of the FID cathode was developed. The efficiency of certain schemes for the laser stepwise and two-photon excitation of atoms was compared for determination of Na.
RESUMO
The laser atomic-ionization (AI) method has been developed for determination of caesium in flames. The limit of detection for caesium in pure aqueous solution is 4 pg ml . The interference of Li, Na, K, Rb, Ca and Fe with the AI signal of caesium has been investigated and explained. The analytical potential of this method has been demonstrated by determination of caesium in water samples, in the concentration range 0.1-1 ng ml .
