Role of iron modifier on boron atomization process using graphite furnace-atomic absorption spectrometry based on speciation of iron using X-ray absorption fine structure

摘要

The role of an Fe modifier on boron atomization process using graphite furnace-atomic absorbance spectrometry was investigated using a spectroscopic approach. The initial state of the Fe modifier in a pyrolytic graphite (PG) furnace was trivalent. With an increase in pyrolysis temperature, the Fe modifier was reduced in a stepwise manner. Fe2O3 and Fe3O4 were dominant at pyrolysis temperatures below 1300 K. From 1300 to 1500 K, FeO was dominant. At temperatures higher than 1700 K, Fe metal was dominant. After a drying step, 17.7% of the initial B remained in the PG furnace. After the pyrolysis step at 773 K, the residual fraction of B was similar to that after the drying step. After the pyrolysis step at a temperature of 1073 K, the residual fraction was 11.7%. At pyrolysis temperatures 1738 K, the residual fraction was 3.3% (limit of detection). In the absence of the Fe modifier, B was not detected, even after the drying step. The Fe modifier acted as an adsorbent and retentive agent for B in the PG furnace during the drying and pyrolysis steps. Our results showed that improvement of B absorbance in the presence of the Fe modifier was owing to B retention by Fe oxide with a high oxidation number. The variation of B absorbance with increasing pyrolysis temperature could be explained by differences in the B retention capacity of Fe species in the PG furnace. (C) 2018 Elsevier B.V. All rights reserved.