SOME PROCESSES OCCURRING IN GRAPHITE FURNACES USED FOR ELECTROTHERMALATOMIC-ABSORPTION SPECTROMETRY IN THE PRESENCE OF ORGANIC-CHEMICAL MODIFIERS

Under stabilized-temperature platform furnace (STPF) conditions ascorb ic acid does not significantly affect the peak areas for lead and tin and increases the peak area 1.37-fold for gallium. The appearance time s for all three elements increase in the presence of ascorbic acid. Th e thermal decomposition of a number of organic chemical modifiers in a n argon atmosphere was studied by means of thermal and elemental analy sis. It was shown that the ascorbic acid melt wets lead and gallium ox ides better than the glucose melt. By the use of an electron microprob e it was shown that after drying and ashing at 500 degrees C of a solu tion containing ascorbic acid, lead and gallium, only 7% and 14% of th e corresponding metal was retained on the surface of the carbon residu e. For glucose the values were 25% and 30%, respectively. It is propos ed that the increase in appearance time for the analytes studied in th e presence of ascorbic acid is a result of their diffusion from the ca rbon residue at the atomization stage. The sensitivity enhancement in the presence of ascorbic acid, which was observed earlier for lead, ti n and a number of other elements, was caused by the substantial change s in the composition of the gas phase in the electrothermal analyser u nder non-STPF conditions.