A method is proposed for the determination of selenium at low concentration in coal by collision/reaction cell technology inductively coupled plasma mass spectrometry (CRC-ICP-MS). Samples were decomposed by high pressure microwave-assisted wet digestion (MAWD) using 250 mg of coal, a mixture of 5 mL of 14.4 mol L−1 HNO3 and 1 mL of 40% HF and 70 min of heating program (200 °C and 40 bar). Hydrogen gas used in the collision/reaction cell was investigated to minimize the argon-based interferences at m/z 77, 78 and 80. The rejection parameter (RPq) and the H2 gas flow rate were set to 0.45 and 4.8 mL min−1, respectively. The use of H2 in the cell resulted in other polyatomic interferences, such as 76Ge1H+, 79Br1H+ and 81Br1H+, which impaired Se determination using 77Se, 80Se and 82Se isotopes, thus Se determination was carried out by monitoring only 78Se isotope. Selenium was determined in certified reference materials of coal (NIST 1635 and SARM 20) and an agreement better than 95% was observed between the results obtained by CRC-ICP-MS and the certified values. Under optimized conditions, the instrumental limit of detection was 0.01 μg L−1 and the method limit of detection was 0.01 μg g−1, which was suitable for Se determination at very low concentration in coal.
Bibliographical noteThe authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Grant 309297/2016-8), Instituto Nacional de Ciência e Tecnologia de Bioanalítica – INCTBio (CNPq Grant Nr. 573672/2008-3) and Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS, Grants16/2551-0000 (182-0) and 16/2551-0000516-8) for supporting this study. Funding for the sample collection provided by NERC Security of Supply programme UK (grant NE/L001764/1).
- Collision/reaction cell
- Selenium determination
- Selenium interferences