基于激光的复杂地质样品绿色高效前处理技术研究

Laser-based Green and Efficient Sample Preparation Procurement for Geological Samples with Complex Matrices

全岩地质样品主微量元素组成分析可为研究地球演化、矿床成因、矿产资源分布等地球科学问题提供重要的基础数据。激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)技术可以直接固体进样,避免了传统分析技术繁琐的湿化学消解流程,不仅低污染、低消耗,而且分析速度快,已经成为最有力的元素分析手段之一。但激光剥蚀进样量小,采样无法代表复杂、不均一样品的化学组成,阻碍了其在全岩主、微量元素分析中的应用。将复杂地质样品制备成均一、稳定的样品靶,是开发LA-ICP-MS全岩地质样品分析方法的关键。本文建立了针对复杂地质样品LA-ICP-MS全岩分析的绿色、高效前处理技术。首先将样品在1000~1100℃下煅烧去除挥发份,压制成片后用高能量、宽脉宽红外激光照射熔融,最终得到均一、稳定的样品玻璃。相比直接粉末压片的样品,该技术将海洋沉积物标准物质GBW07354和GBW07356中各元素的平均分析精密度分别提高了7.7倍和3.9倍。优化后的前处理技术已应用于海洋沉积物、土壤和铝土矿标准物质中主微量元素的快速准确分析。海洋沉积物标准物质中大部分元素的测试值与参考值的相对偏差都在10%以内;土壤成分标准物质中大部分主量元素、稀土元素(REEs)、其他微量元素的测试值与参考值的相对偏差分别在5%、20%和15%以内;铝土矿标准样品中测试元素达到40个,首次给出了Sc和W元素的参考值。本文建立的样品前处理技术可快速将海洋沉积物、土壤和铝土矿标准样品制备成均一稳定的玻璃,使LA-ICP-MS技术可直接较好地应用于复杂地质全岩样品(海洋沉积物、土壤和铝土矿)元素分析中,进一步提高了地质样品主微量元素的测试效率。

BACKGROUND:Knowledge of the chemical composition of whole-rock geological samples is the basic work of geochemical research.Laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)has become the most powerful tools of elemental analysis as its advantages of direct solid sampling,avoiding the cumbersome wet chemical digestion process of traditional analytical techniques,low-pollution and low-consumption and high-efficiency.However,the small sample volume of laser ablation cannot represent the chemical composition of complex and inhomogeneous samples,resulting in poor analytical precision and accuracy,which hinders its application in whole-rock bulk analysis.It is critical to prepare complex whole-rock geological samples into homogeneous and stable sample targets.OBJECTIVES:To establish a green and efficient pretreatment technique for LA-ICP-MS whole rock analysis of complex geological samples.METHODS:The samples were first calcined at 1000-1100℃to remove volatiles,pressed into pellets,and then melted by high-energy wide pulse width infrared laser irradiation to finally obtain a homogeneous and stable sample glass.RESULTS:Compared with pressed powder pellets,the new sample preparation procurement improved the analytical precision of each element in marine sediments GBW07354 and GBW07356 by an average of 7.7 times and 3.9 times,respectively.The deviation between the measured values and reference values of most elements in marine sediment samples was within 10%;the deviation between the measured values and reference values of most major elements,REEs,and other trace elements in soil composition standards was within 5%,20%,and 15%,respectively;the number of elements measured in bauxite samples reached 40,and the compositions of Sc and W elements were given for the first time.CONCLUSIONS:Rapid and accurate analysis of major and trace elements in marine sediment,soil,and bauxite standard samples has been determined through the optimized pretreatment technique.The sample preparation procurement established in this paper allows the LA-ICP-MS technique to be directly and better applied to the elemental analysis of complex geological whole rock samples,further improving the efficiency of major and trace element analysis in geological samples.