微波消解-电感耦合等离子体质谱法测定煤中的硼

煤中硼的准确测定对于研究成煤的沉积环境具有重要意义。微波消解-电感耦合等离子体质谱(ICP-MS)可以有效地测定煤中的大部分微量元素,但由于硼易挥发等特殊的物理化学性质,致使硼的测定过程较为繁琐,测试结果不够准确。本文对微波消解ICP-MS测定煤中硼含量的分析方法进行了改进。样品中加入磷酸、硝酸和氢氟酸,用微波消解仪消解完全,置于电热板加热赶酸完毕后用硝酸提取。硼的卤化物易挥发,磷酸的加入使硼与磷酸结合生成难挥发的稳定络合物,起到了固硼的作用。ICP-MS测定中采用铍作为内标,通过在线加入的方式有效地补偿了基体效应产生的影响;用稀氨水冲洗进样系统,很好地降低了硼的记忆效应;选择高分辨率模式来测定,避免了12C和40Ar4+等质谱峰的干扰。方法的仪器检出限(0.22ng/mL)和方法检出限(0.34 ng/mL)较低,方法精密度(RSD)小于0.6%,灵敏度高,且测定标准样品的准确度良好。该方法简单快速,适用于批量分析煤样中硼的含量。

Determination of Boron in Coal Samples with Microwave Digestion by Inductively Coupled Plasma-Mass Spectrometry

Accurate determination of boron in coal is significant to the understanding of the original peat-forming environment. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is a reliable technique to determine most trace elements in coal samples. However, the procedure for the determination of boron is complex and the results are inaccurate, due to the special chemical and physical properties of boron, such as high volatility. In this study attempts to determine boron in coal samples using an improved procedure of ICP-MS technique with microwave digestion are made. Samples were digested in a microwave oven with H₃PO₄, HNO₃ and HF, and then were heated to remove acid on the heating plate. Due to the high volatility of halogenides of boron, phosphoric acid was added to chelate the boron which minimizes boron volatilization during heating. Beryllium was added online as the internal standard, which compensated for matrix effects. Diluted ammonium hydroxide solution was used as the wash solution, which significantly reduced the memory effect of boron. Measurement was taken under high resolution mode, in order to minimize spectral interference from ¹²C and ⁴⁰Ar⁴⁺. The instrument detection limit was 0.22 ng/mL, and the method detection limit was 0.34 ng/mL with high sensitivity and accuracy, verified by standard materials. The results show that this method is a simple and rapid procedure, and can be used for routine determination of boron for batch coal samples.