Determination of boron in coal using closed-vessel microwave digestion and inductively coupled plasma mass spectrometry (Icp-Ms)

Boron in coal is of great interest, mainly because it can be used as paleosalinity indicator; it is also of environmental concern because of its toxic effects, especially on land plants. This paper describes a new method for determination of the boron concentration in coal by inductively coupled plasma mass spectrometry (ICP-MS) after closed-vessel microwave digestion. Samples of raw coal rather than coal ash were used for the determination to avoid the loss of volatile organically bound boron. Addition of H₃PO₄ to the HNO₃ and HF used as reagents in the process could also significantly diminish boron volatilization during acid-drying after sample digestion. A 2% ammonia solution, which was injected into an ICP-MS spray chamber to eliminate the memory effect of boron, may reduce boron signals to blank levels (within 120 s) during ICP-MS analysis. The boron concentrations of National Institute of Standards and Technology (NIST) standard reference coal samples obtained using the ICP-MS in high-resolution mode and with ¹⁰³Rh or ¹¹⁵In used as online addition internal standards are in good agreement with the certified values.