Determination of Se at low concentration in coal by collision/reaction cell technology inductively coupled plasma mass spectrometry

Highlights: • Selenium was determined at low level in coal by CRC-ICP-MS. • Hydrogen was feasible to minimize the argon-based interferences at m/z 77, 78, 80 and 82. • The limit of detection was 50 times better than that obtained using the standard mode ICP-MS. 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.