Determination of strontium by graphite furnace atomic absorption

Pyrolytic graphite coated tubes with and without totally pyrolytic graphite platforms and uncoated polycrystalline electrographite tubes and Ar or N as pure gas are used. Signals for Sr in nitric acid medium are obtained. The optimum pyrolysis temperatures are similar for all conditions. Lower appearance time, 0.2 s, and lower characteristic mass, 0.8 pg/0.0044 A.s, are obtained for atomization from the wall of pyrolytic coated tubes in argon. Coating the tubes with tungsten by the soaking method does not increase the signal. Much lower sensitivity is obtained when nitrogen is used due to the favoured formation of gaseous thermostable monocyanides. A tailing in the peak shape, not as pronounced as for barium when argon is used instead of nitrogen, could indicate gaseous carbide formation. Scanning electron micrographs of the graphite surfaces are discussed in connection to the other data. (author)