Reversed Micellar Mediated Luminol Chemiluminescence Detection of Iron(II, III) Combined with On-Line Solvent Extraction Using 8-Quinolinol

Abstract

An enhancement of the chemiluminescence (CL) emission, observed when the iron(III) complex of 8-quinolinol (oxine), Fe(oxine)₃, was mixed with a reversed micellar solution of cetyltrimethylammonium chloride in chloroform-cyclohexane (6:5 v/v)-water (1.0 M NaOH) containing luminol and hydrogen peroxide, was investigated in order to develop a method for iron(III) determination based on the direct coupling of on-line solvent extraction with a reversed micellar-mediated CL reaction in a reverse-flow injection system using a microporous Teflon membrane filter for phase separation. In the CL process, uptake of the complex by reverse micelles and its subsequent decomposition occurs easily, followed by an iron(III)-catalyzed luminol reaction. In the on-line process, iron(III) was extracted from an aqueous solution into chloroform via complex formation with oxine. Upon mixing the reversed micellar luminol solution with the extract stream in a flow cell of a CL monitor, the produced CL signal was measured. A detection limit of 5 ng cm^-3 Fe(III) and a linear calibration graph was obtained in the concentration range of 10 - 500 ng cm^-3 Fe(III). In a sample solution containing iron(II) and iron(III), total iron, Fe(II)+Fe(III), was measured as the peak height in the presence of the hydrogen peroxide used to oxidize iron(II) to iron(III) prior to solvent extraction, while only iron(III) could be determined in the absence of hydrogen peroxide.