NANOTOPOGRAPHICAL CHANGES ON GRAPHITE TUBE SURFACES IN ELECTROTHERMALATOMIC-ABSORPTION SPECTROMETRY EXPERIMENTS AS STUDIED BY ATOMIC-FORCEMICROSCOPY

Atomic force microscope images of surfaces of graphite tubes used in c hromium determinations in electrothermal atomic absorption spectrometr y (ET-AAS) reveal severe topographical modifications on both the micro meter and the nanometer scale after only a few atomisation cycles. A p reviously undescribed nanostructure has been found on unused and also on used graphite tubes. During the first atomisation cycles the protru sion size distribution is found to become more uniform, which is in ag reement with the observed increase in reproducibility of ET-AAS measur ements after some 10 to 20 analysis cycles. The homogenisation of the graphite surface is interpreted as the initial phase of a secondary co ating.