Overcoming interference from the alumina matrix on the determination of arsenic at 189 nanometers using electrothermal atomic absorption spectrometry

A method is described enabling to eliminate the spectral interference from alumina matrix onto As determination at the wavelength 189 nm by electrothermal atomic absorption spectrometry with deuterium background correction. Matrix modification was performed by the addition of ammonium fluoride to protect the formation of aluminium oxide implicated in causing spectral interference and to increase volatility of alumina matrix via the formation of AlF3. Pre-treating of the pyrolytic graphite platform with a solution of rhodium and citric acid has enabled to stabilize the analyte up to temperature of 1300 °C at which most of AlF3 could be removed from the graphite furnace. The application of 2 μg of Rh + 20 μg of citric acid + 200 μg of NH4F has enabled an accurate and interference-free determination of As up to 40 μg of Al in the form of AlCl3 as verified by analytical recoveries study and resulted in characteristic mass and LOD value in the original sample 15 pg and 50 ng g−1, respectively (10-μL aliquots of sample).