SS-FF-AAS AS AN ALTERNATIVE TECHNIQUE FOR ELEMENTAL IMPURITIES DETERMINATION IN HIGH PURITY GRAPHITE

The solid sampling flame furnace atomic absorption spectrometry (SS-FF-AAS) system was proposed for the determination of Cu in high purity graphite without a previous sample preparation step. A homemade quartz tube, with two perpendicular tubes, (T-shaped tubes) were positioned above the burner of the flame atomic absorption spectrometer. Graphite samples were pressed as a pellet, positioned inside the quartz T-tube (Fig 1A and 1B) and reached up to the T-connection (above the burner). In this part, with high temperature and in the presence of controlled O2-flow, sample burns and the products were transferred to the upper slit tube, where the atomization and absorption process occurs. The flame stoichiometry and oxygen flow-rate were evaluated to allow calibration using aqueous reference solutions which was added directly on the cleaned graphite carrier (free from Cu). During determination step, no mass influence was observed from 7 to 75 mg of sample. The transient analytical signal was integrated for 60 s (Fig 1C). The accuracy was evaluated by Cu determination using ICP-MS with previous step of sample digestion. The agreement was higher than 94% for all samples and no statistical difference was observed (ANOVA, 95%). The proposed SS-FF-AAS was considered suitable for Cu determination at trace levels in graphite powder, presenting high sensibility (characteristic mass: 720 pg) and low limits of detection (0.3 μg g-1).