title: Rapid determination of surfactant critical micelle concentration in aqueous solutions using fiber-optic refractive index sensing.
abstract: We describe a simple and rapid method for determining the critical micelle concentration (CMC) of surfactants from fiber-optic measurements of refractive index. The refractive index of an aqueous surfactant solution was monitored as the surfactant concentration was increased using an automated dispensing system. On reaching the surfactant's CMC value, an abrupt change was observed in the rate of increase of the refractive index with increasing concentration. The measurement system provides rapid semiautomatic data collection and analysis, increasing the precision, sensitivity, and range of applicability of the technique while substantially decreasing the amount of manual intervention required. Measurements of CMC for sodium dodecyl sulfate (8.10mM), cetyltrimethylammonium chloride (1.58mM), and Triton X-100 (0.21mM) were in excellent agreement with values previously reported in the literature. The method is applicable to cationic, anionic, and nonionic surfactants, and it offers a facile, in situ, and sensitive means of detecting micelle formation over a broad range of CMC values larger than 10(-1)mM.
authors.affiliation: Laboratory of Photonic Information Technology, School for Information and Optoelectronic Science and Engineering, South China Normal University, 510631 Guangzhou, China.
authors.forename: Chun Hua
authors.initials: CH
authors.lastname: Tan
authors.forename: Zhen Jian
authors.initials: ZJ
authors.lastname: Huang
authors.forename: Xu Guang
authors.initials: XG
authors.lastname: Huang
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000032:analysis; D008823:Micelles; D017830:Octoxynol / Q000032:analysis; D012031:Refractometry / Q000379:methods*; D012967:Sodium Dodecyl Sulfate / Q000032:analysis; D013501:Surface-Active Agents / Q000032:analysis / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D008823:Micelles; D013501:Surface-Active Agents; D014867:Water; D012967:Sodium Dodecyl Sulfate; D017830:Octoxynol; D000077286:Cetrimonium