Flow-injection chemiluminescence method for determination of critical micelle concentration of surfactants

Abstract

In this study, chemiluminescence (CL) behaviour of Luminol-H₂O₂ in the presence of the different concentrations of four surfactants, cetyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), sodium dodecyl sulphate (SDS) and polyoxyethylene dodecyl ether (Brij-35), was investigated. A novel method for the direct determination of critical micelle concentration (CMC) of the surfactants using flow-injection CL is described. Under the optimum conditions, the luminescence intensity of the Luminol-H₂O₂ system increased gradually with increasing concentration of the surfactants before the CMC, but rapidly reached to the emission maximum at the CMC, followed by a decrease after the CMC. The concentrations of the surfactants corresponding to the luminescence maximum are in agreement with the literature CMC values. The main factors affecting the determination of CMC are discussed. The mechanistic studies show that the luminescence peaks observed in the experiment were mainly because of the protective effect of the micelle against the transition of the excited species and the retarding effect of the micelle structures on the CL reaction rate.

Keywords:

• flow-injection
• chemiluminescence
• critical micelle concentration
• surfactant

Additional information

Funding

This study was supported by the National Natural Science Foundation of China [grant number 21307015]; the Project of Science and Technology New Star of Pearl River of Guangzhou city [grant number 2012J2200055]; the Distinguished Young Teachers in Higher Education of Guangdong, China [grant number Yq2013122]. The authors are grateful to the projects.