Feasibility of employing permanent chemical modifiers for the determination of cadmium in coal using slurry sampling electrothermal atomic absorption spectrometry
- 作者：Liane Bianchin ; Daniela Nadvorny ; Alessandra Furtado da Silva ; Maria Goreti Rodrigues Vale ; Má ; rcia Messias da Silva ; Walter N.L. dos Santos ; Sergio L.C. Ferreira ; Bernhard Welz and Uwe Heitmann
- 关键词：Electrothermal atomic absorption spectrometry ; Slurry sampling ; Cadmium determination ; Coal analysis ; Permanent chemical modifiers ; Background correction ; High-resolution continuum source AAS
- 刊名：Microchemical Journal
- 出版年：2006
- 期刊代码：64_0026265x
- 类别：ce
- 出版时间：April 2006
- 卷：82
- 期：2
- 页码：174-182
- 文件大小：272 K
摘要
Iridium and ruthenium, alone and in combination with tungsten, thermally deposited on the platform of a transversely heated graphite tube, were investigated for their suitability as permanent chemical modifiers for the determination of cadmium in coal slurries by electrothermal atomic absorption spectrometry (ET AAS). The conventional mixed palladium and magnesium nitrates (Pd–Mg) modifiers, added in solution, were also investigated for comparison. The latter one showed the best performance for aqueous solutions, and the mixed W–Ir and W–Ru permanent modifiers had the lowest stabilizing power. All of the investigated modifiers lost some of their stabilizing power when coal slurries were investigated. The Pd–Mg modifier, pure Ir and Ru, and a mixture of 300 μg W + 200 μg Ir could stabilize Cd at least to a pyrolysis temperature of 600 °C, whereas all the other combinations already failed at temperatures above 500–550 °C. Additional investigations of the supernatant liquid of the slurries supported the assumption that the high acid concentration of the slurries and/or a concomitant leaching out of the coal might be responsible for the reduced stabilizing power of the modifiers. The maximum applicable pyrolysis temperature of 600 °C was not sufficient to reduce the background absorption to a manageable level in the majority of the coal samples. High-resolution continuum source ET AAS revealed that the continuous background absorption was exceeding values of A = 2, and was overlapping with the analyte signal. Although the latter technique could correct for this background absorption, some analyte was apparently lost with the rapidly vaporizing matrix so that the method could not be considered to be rugged. A characteristic mass of 1.0 pg and a detection limit of 0.6 ng g− 1 could be obtained under these conditions.