DETERMINATION OF TRACE IMPURITIES IN HIGH-PURITY GRAPHITE BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY AND INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

The process for the determination of B and Si in high-purity graphite used for spectral analysis elaborated here, is based on matrix combust ion without any loss of analyte in an oxygen atmosphere with the addit ion of alkali. Sub-boiling distilled nitric acid and water were used t o dissolve ashes. Silicon, B, Cd and Cu were determined by inductively coupled plasma atomic emission spectrometry and the other elements (C r, Co, Mo, V, Ni and Ti) were determined by electrothermal atomic abso rption spectrometry. Carbon is the most commonly used material in the production of electrodes for emission spectral analysis as well as bei ng the material of electrothermal atomizers used in atomic absorption analysis. The level of impurity should not be greater than 10(-5)-10(- 6)%. The purifying processes used in the production of carbon electrod es for spectroscopy are adequate for obtaining these values for most e lements, with the exception of B, Si and those elements whose carbides are extremely non-reactive. Precision, given as the relative standard deviation for both Si and B at the ppm level was within 10%. The accu racy of the whole procedure was controlled using spiked samples.