In-situ electrothermal fluorination-assisted matrix removal, slurry sampling, graphite furnace atomic absorption spectrometry for the determination of trace-level chromium, cobalt and vanadium in zirconium dioxide powder

Abstract

An in-situ electrothermal fluorination-assisted matrix removal method was developed with PTFE as chemical modifier, and trace-levels of Cr, Co and V in ZrO2 powder were determined. The solid samples were directly introduced into the graphite furnace in the form of a slurry, where the Zr matrix reacted with the active carbon fluoride formed by electrothermal decomposition of PTFE during the pyrolysis stage. Without loss of analytes, the Zr matrix was completely vaporized and removed by the carrier gas. As a result, the matrix interference, which was serious without the modifier, was effectively suppressed, and the chemical attack of the excess of the Zr matrix on the graphite tube was also minimized. The standard additions calibration and the aqueous standard calibration were compared and similar results were obtained. The removal of matrix, the background absorption, the chemical modification of PTFE and the temperature–time program of the graphite furnace were investigated and optimized. The proposed method was applied to the direct determination of trace amounts of Cr, Co and V in ZrO2 powder with aqueous calibration and the results obtained were in good agreement with those obtained by pneumatic nebulization ICP-AES after digestion and separation of the matrix Zr with PMBP extraction. The detection limits of Cr, Co and V were 0.20, 0.32 and 3.7 µg g−1, respectively.