Complete evaporation by electrothermal heating and equilibrated dissociation in a flame are combined in furnace-in-flame atomizers to give relative freedom from effects of both the matrix composition and the state (solid or solution) of the sample. Efforts have been made to improve the ease of adaptation to commercial equipment and to ensure long-term operation by using a simple graphite cup and an acetylene-air flame for both solutions and solid samples. Relative sensitivities (20 μl of solution) are typically 4-10 times better than with conventional flame techniques for the 15 elements studied. Solid alumina and residues from evaporated solutions were heated at a relatively low rate (ramp mode) to attain sodium evaporation during 30 sec and the signal was integrated over this time. The alignment of the observation zone relative to the lip of the cup was critical in comparing analytical curves from solid and solution standards. The direct determination of sodium in alumina at the ppm level is fast, inexpensive and precise enough (RSD 9-16%) with the present technique. A detection limit of 0.3 ppm Na has been attained, but should be still lower for work in a "clean" laboratory.
ASJC Scopus subject areas
- Analytical Chemistry