ANALYTICAL CHARACTERIZATION OF LASER-EXCITED ATOMIC FLUORESCENCE OF BISMUTH

The possibilities of direct determination of Bi traces by laser excited atomic fluorescence spectrometry were investigated. Practically all one-color excitation-detection schemes were examined. For the resonance fluorescence at 306.8 nm, the main source of background was a molecular fluorescence of residual water vapors. The background characteristic OH rotational lines of 0-0 band of (2) Sigma - (II)-I-2 transition were registered in the excitation spectra. From the relative intensities of the rotational components, the gas temperature of the analytical volume above the open graphite cup of the atomizer was estimated as 680 +/- 120 degrees C. A detection limit (LOD) of about 1 pg/ml was achieved for the resonance scheme. For the excitation wavelength shorter than 230 nm, broadband fluorescence of unidentified species in the 300-400 nm spectral range was the main source of background. The best LOD of 0.05 pg/ml was realized for the 223.1/299.3 nm excitation-detection scheme. This LOD is the best one for the one-color LEAFS technique. Possible ways of further increasing the LEAFS sensitivity of Bi traces detection are briefly discussed.