Abstract
Absorption spectra of various salts such as alkali metal salts, alkaline earth dichlorides, and ammonium halides were investigated and absorptions of some molecular species produced in the carbon tube were identified. The aqueous solution (20 μl) containing 1.0 mg/ml of each salt was placed in the carbon tube atomizer and heated in a similar manner to usual flameless atomic absorption method. D2-lamp was used as a continuous light source and argon gas was employed as an inert sheath gas. The spectra were obtained over the range of wavelength 200 to 350 nm.
When alkali halides were feeded, the absorption spectra agreed with those of alkali halide vapors. Therefore, in such cases vapors of the alkali halides were probably produced by the sublimation or vaporization in the atomizer. The spectra of alkali perchlorates were considered to be those of alkali chlorides produced by the pyrolysis of the perchlorates in the atomizer. The absorptions of alkaline earth chlorides below 250 nm were probably due to their gaseous states. Sulfur dioxide was found to be produced by the pyrolysis of alkali sulfates, bisulfates and sulfites in the atomizer. Alkali phosphates and pyrophosphates gave almost identical spectra below 300 nm. Gamma band spectrum of nitrogen monoxide was observed from 200 to 240 nm during ashing at about 330°C for alkali nitrates and nitrites. Ammonia vapor was produced from ammonium halides during drying at about 170°C.
Although the absorptions of alkali carbonates and hydroxides were almost undetectable, the same spectra as those of alkali halides were observed by the addition of ammonium halides to the solutions of alkali compounds. This shows that alkali halides are produced in the atomizer by the addition of halide ions.
