Analysis of trace metals and organic substances often rely on the use of
organic solvent-based extractions. In this laboratory exercise, students
will use analytical chemistry to determine heavy metals from water samples
using a greener, micelle-mediated extraction procedure called a cloud-point
extraction. Water samples are treated with a chelating agent, ammonium
pyrrolidinedithiocarbamate, and the nonionic surfactant Triton X-114. After
acidifying the solution, samples are heated to promote micelle formation and
heavy metals are removed with the surfactant-rich phase. Samples are heated
to remove remaining water and then prepared for atomic absorption
spectroscopy operating in the flame mode. Developed for an undergraduate
analytical chemistry laboratory this exercise focuses on the fundamental
concepts of micelle formation, phase separation and cloud-point extraction
methodology. The greener, micelle mediated preconcentration technique
replaces high volume, more hazardous organic solvent extraction methods.
Supplemental materials are provided on the J. Chem. Educ. website and include instructor notes.
Summary prepared May 2005 by Julie A. Haack, Department of Chemistry at the University of Oregon.
Giokas, D. L.; Paleologos, E. K.; Karayannis, M. I. J. Chem. Educ., Print 2003, 80, pp 61-64.