Analysis of high purity boron carbide by solid sampling graphite furnace atomic absorption spectrometry

Abstract

An alternative method for the determination of metallic impurities in high purity boron carbide (B₄C) using solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) was proposed. The feasibility of using a Zeeman-effect background correction system operating with a variable magnetic field (VMF) was evaluated to provide a large working range for Al, Cr, Cu, Mn and Ni determination in B₄C samples. The following parameters were evaluated: pyrolysis and atomization temperatures, sample mass, as well as the use of alternative wavelengths for Al and Mn. As an important achievement, calibration using aqueous standard solutions was feasible and chemical modifiers were not necessary. However, it was observed that the use of graphite powder to cover the sample platform avoided the damage of the pyrolytic layer of the graphite platform. Working ranges from 0.01 to 1500 μg g⁻¹ were obtained for the metallic impurity determination by SS-GFAAS. Sample masses up to 2.5 mg were used providing limits of detection ranging from 0.003 to 1 μg g⁻¹, with a RSD lower than 17%. The accuracy was evaluated using the B₄C certified reference material (BAM/ERM-ED 102) and by comparison of the results obtained by microwave-assisted-wet digestion and alkaline fusion with subsequent determination by inductively coupled plasma optical emission spectrometry (ICP-OES). No differences were observed between the results obtained by SS-GFAAS and those by ICP-OES after both digestion methods (t-test, 95% confidence level). Additionally, the results presented no significant differences with the values of the certified reference material. The proposed SS-GFAAS method allowed quality control related to determination of Al, Cr, Cu, Mn and Ni in B₄C with a large working range and limits of detection lower than those achieved by other methods reported in the literature.