Determination of Boron in Coal Using Closed-Vessel Microwave Digestion and Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

Abstract

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.