Department of Environmental Engineering, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, D-04318 Leipzig, Germany.
Environ Sci Technol. 2011 Dec 1;45(23):10013-9. doi: 10.1021/es2023835. Epub 2011 Nov 10.
This study presents a new experimental technique for measuring rates of desorption of organic compounds from dissolved organic matter (DOM) such as humic substances. The method is based on a fast solid-phase extraction of the freely dissolved fraction of a solute when the solution is flushed through a polymer-coated capillary. The extraction interferes with the solute-DOM sorption equilibrium and drives the desorption process. Solutes which remain sorbed to DOM pass through the extraction capillary and can be analyzed afterward. This technique allows a time resolution for the desorption kinetics from subseconds up to minutes. It is applicable to the study of interaction kinetics between a wide variety of hydrophobic solutes and polyelectrolytes. Due to its simplicity it is accessible for many environmental laboratories. The time-resolved in-tube solid-phase microextraction (TR-IT-SPME) was applied to two humic acids and a surfactant as sorbents together with pyrene, phenanthrene and 1,2-dimethylcyclohexane as solutes. The results give evidence for a two-phase desorption kinetics: a fast desorption step with a half-life of less than 1 s and a slow desorption step with a half-life of more than 1 min. For aliphatic solutes, the fast-desorbing fraction largely dominates, whereas for polycyclic aromatic hydrocarbons such as pyrene, the slowly desorbing, stronger-bound fraction is also important.
本研究提出了一种新的实验技术，用于测量有机化合物从溶解有机物（DOM）如腐殖质中解吸的速率。该方法基于当溶液通过聚合物涂覆的毛细管冲洗时，快速固相萃取溶质的自由溶解部分。这种萃取会干扰溶质-DOM 吸附平衡并驱动解吸过程。仍被 DOM 吸附的溶质通过萃取毛细管并可以随后进行分析。该技术允许对亚秒至数分钟的解吸动力学进行时间分辨。它适用于研究各种疏水性溶质和聚电解质之间的相互作用动力学。由于其简单性，它可以为许多环境实验室所接受。时间分辨管内固相微萃取（TR-IT-SPME）与腐殖酸和表面活性剂一起用于两种腐殖酸和一种表面活性剂，以及芘、菲和 1,2-二甲基环己烷作为溶质。结果表明存在两相解吸动力学：半衰期小于 1 秒的快速解吸步骤和半衰期超过 1 分钟的缓慢解吸步骤。对于脂肪族溶质，快速解吸部分占主导地位，而对于多环芳烃如芘，缓慢解吸、更强结合的部分也很重要。
