Capillary Electrophoresis System for Water Quality Analyses and Interpretations in the Undergraduate Geochemistry Laboratory

毛细管电泳法(CE)系统的获得使分析天然水样中溶解的无机和有机阴离子成为可能。常规分析溶解的阴离子以评估水质，补充电感耦合等离子体原子发射光谱分析(ICPAES)分析溶解的阳离子。这些数据是在包括水-岩石相互作用、污染物迁移和碳循环在内的地球化学过程背景下理解自然水组成的基础。水中溶解的阴离子的分析通常是用离子交换层析来完成的。然而，最近在水样中应用毛细管电泳法比离子交换法有许多优点，特别是在学术环境中。CE系统具有更少的移动部件、更便宜的柱、更少的溶剂废液体积和更快的分析速度。地质学专业的高年级本科生正在学习水相地球化学的概念(例如，平衡、活度和浓度关系，以及矿物的溶解度)。可以应用这些概念来了解管理天然(和可能受到污染的)地下水和地表水样本的过程。学生通过六个部分的练习，完成以下任务：现场采集水样；准备分析水样；用CE分析样本中的阴离子；用电感耦合等离子体发射光谱分析样本中溶解的阳离子；用图形方法对水质数据进行定性解释；以及通过计算机模型对水质数据进行定量解释。除了在本科生层面提供跨学科的教育和研究机会外，获得一名CE还增强了该部门开发专注于水质分析的本科生实验室练习的能力。

The acquisition of a capillary electrophoresis (CE) system enables analyses of dissolved inorganic and organic anions in natural water samples. Dissolved anions are analyzed routinely to assess water quality, supplementing the analysis of dissolved cations by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) methods. These data are fundamental to an understanding of natural water compositions in the context of geochemical processes including water-rock interactions, contaminant migration, and carbon cycling. Analysis of dissolved anions in water is commonly accomplished using ion-exchange chromatography. However, recent application of CE methods to water samples presents many advantages over ion-exchange methods, especially in an academic setting. CE systems have fewer moving parts, less expensive columns, smaller solvent waste volumes, and faster analyses. Upper-level undergraduate geology majors in the Introduction to Geochemistry course are being instructed in the concepts of aqueous geochemistry (for example, equilibrium, activity and concentration relationships, and mineral solubility). These concepts can be applied in order to understand the processes governing natural (and possibly contaminated) ground and surface water samples. Students proceed through a six-part exercise in which they perform the following tasks: collect water samples in the field; prepare water samples for analysis; analyze samples for anions by CE; analyze samples for dissolved cations by ICP-AES; perform qualitative interpretation of water-quality data by graphical methods; and perform quantitative interpretations of water-quality data by computer models. In addition to providing interdisciplinary educational and research opportunities at the undergraduate level, acquisition of a CE enhances the department's ability to develop undergraduate laboratory exercises focusing on water-quality analysis.