Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
Department of Civil and Environmental Engineering, University of Nevada, Reno, NV, 89523, USA.
Water Res. 2017 Oct 1;122:337-344. doi: 10.1016/j.watres.2017.06.010. Epub 2017 Jun 12.
Fluorescence quenching is a sensitive and fast method to quantify the interactions between a fluorescent organic contaminant and a quencher, such as dissolved organic matter (DOM). Dynamic fluorescence quenching is resulted from molecular collision, not the real binding, and thus it complicates the binding data interpretation. On the other hand, static fluorescence quenching occurs for fluorescent contaminants of ground states, which decreases the concentration of freely dissolved contaminants. However, how a particular structure in DOM contributes to the static and dynamic fluorescence quenching of a fluorescent contaminant is still unclear, which has greatly hindered the application of fluorescence quenching technique. A humic acid (HA) extracted from sediment was chemically modified, i.e., bleaching, acid hydrolysis, and decarboxylation. HAs before and after these modifications were used in fluorescence quenching experiments for phenanthrene (PHE), 9-phenanthrol (PTR) and naphthalene (NAP). Different quenching mechanisms were observed for these chemicals depending on HA properties. For PHE and NAP, aromatic components showed static quenching, while carboxyl groups primarily showed dynamic quenching. Aromatic components and carbohydrates in HAs primarily bound (static quenching) rather than collided (dynamic quenching) with PTR. Carboxyl groups showed interactions with PTR through dynamic quenching only when carboxyl groups were on the benzene ring. Based on the results, we emphasized that dynamic quenching should be carefully excluded in fluorescence quenching studies. This line of study is important to establish a general relationship between DOM properties and static/dynamic quenching contributions.
荧光猝灭是一种灵敏且快速的方法，可用于定量测量荧光有机污染物与猝灭剂（如溶解有机物 (DOM)）之间的相互作用。动态荧光猝灭是由于分子碰撞引起的，而不是真正的结合，因此它使结合数据的解释变得复杂。另一方面，静态荧光猝灭发生在荧光污染物的基态，这会降低自由溶解污染物的浓度。然而，DOM 中的特定结构如何导致荧光污染物的静态和动态荧光猝灭仍然不清楚，这极大地阻碍了荧光猝灭技术的应用。从沉积物中提取的腐殖酸 (HA) 经过化学修饰，即漂白、酸水解和脱羧。在这些修饰前后，使用 HA 进行了芘 (PHE)、9-菲咯啉 (PTR) 和萘 (NAP) 的荧光猝灭实验。根据 HA 的性质，这些化学物质观察到不同的猝灭机制。对于 PHE 和 NAP，芳香族成分表现出静态猝灭，而羧基主要表现出动态猝灭。HA 中的芳香族成分和碳水化合物主要通过静态猝灭与 PTR 结合（而不是碰撞），而不是动态猝灭。只有当羧基在苯环上时，羧基才通过动态猝灭与 PTR 相互作用。基于这些结果，我们强调在荧光猝灭研究中应仔细排除动态猝灭。这条研究线对于建立 DOM 性质与静态/动态猝灭贡献之间的一般关系非常重要。
