NANOTOPOGRAPHICAL CHANGES ON GRAPHITE TUBE SURFACES IN ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY EXPERIMENTS AS STUDIED BY ATOMIC-FORCE MICROSCOPY

Atomic force microscope images of surfaces of graphite tubes used in chromium determinations in electrothermal atomic absorption spectrometry (ET-AAS) reveal severe topographical modifications on both the micrometer and the nanometer scale after only a few atomisation cycles. A previously undescribed nanostructure has been found on unused and also on used graphite tubes. During the first atomisation cycles the protrusion size distribution is found to become more uniform, which is in agreement with the observed increase in reproducibility of ET-AAS measurements after some 10 to 20 analysis cycles. The homogenisation of the graphite surface is interpreted as the initial phase of a secondary coating.