Atomic and molecular spectra of vapors evolved in a graphite furnace. Part 3: alkaline earth fluorides

Slurries of alkaline earth fluorides in aqueous and toluene media, 100 μg as element, were vaporized in a pyrocoated and Ir-sputtered graphite furnace during fast heating from 400 to 2500°C. Absorption spectra in the 200–475-nm range were obtained using a dedicated CCD spectrometer. The vaporization of Be, Mg, Ca, Sr and Ba fluorides showed the signs of the evolution of the di-fluorides at low temperature followed by the appearance of the mono-fluorides and atomic vapor. The exothermal interaction of sample vapor with graphite caused the evolution of heat into the furnace gas that substantiated light scattering below 400 nm, emission continuum above 400 nm and reversal of some molecular bands into emission. All the thermal effects were displayed more intensely in the presence of the hydrolysis products in the aqueous slurry. The hydrolysis was suppressed, and the thermal effects were reduced, when the toluene slurries were used. The vapor interaction with graphite was reduced in a great extent in the Ir sputtered tubes, and hence, the spectra of the mono-fluorides were not affected by the overlapping of simultaneous thermal effects.