Migration of Ag, Cd and Cu into highly oriented pyrolytic graphite and pyrolytic coated graphite

Migration of Cd, Cu and Ag from solution deposited samples of the respective nitrates into highly oriented pyrolytic graphite (HOPG) was studied using electrothermal atomic absorption spectroscopy (ETAAS) with platform vaporization. Metal migration was verified by removing the top layers of the HOPG platform after the sample had dried and performing the analysis using ETAAS. The results obtained suggest that the metals or their salts migrate into HOPG only when the sample solutions are deposited on those areas of the platform that have surface imperfections. The surface blemishes can be seen as tiny lines on the otherwise smooth surface of the HOPG platform. One possible driving force for the migration could be simple capillary action; however, additional information is needed to establish the true mechanism.

The effect of metal migration into graphite on atomic absorption profiles was also evaluated. This effect was studied by comparing the signals obtained after the sample had been deposited either on the imperfections or on the smooth areas of the HOPG platform. In addition, samples were atomized from both sides of a pyrolytic coated platform in which one of the sides had been roughened with an abrasive material to expose the electrographite. The main effect of metal migration on the absorption profiles seems to be an increased tailing of the back edge of the signals. This could suggest a secondary generation function limited by the rate of diffusion of the metal back to the substrate surface and subsequent vaporization.