Kinetics of desorption of organic compounds from dissolved organic matter.
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.
Department of Environmental Engineering, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, D-04318 Leipzig, Germany. frank-dieter.kopinke@ufz.de
Frank-Dieter
FD
Kopinke
Ksenia
K
Ramus
Juergen
J
Poerschmann
Anett
A
Georgi
D000327:Adsorption; D003510:Cyclohexanes / Q000737:chemistry; D006812:Humic Substances; D007700:Kinetics; D009930:Organic Chemicals / Q000737:chemistry*; D010616:Phenanthrenes / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry; D052617:Solid Phase Microextraction
D003510:Cyclohexanes; D006812:Humic Substances; D009930:Organic Chemicals; D010616:Phenanthrenes; D011721:Pyrenes; C031181:phenanthrene; C068558:1,2-dimethylcyclohexane; C030984:pyrene