Flow analysis preconcentration of Mg and Zn using emulsions for flame atomic absorption spectrometry

Abstract

A preconcentration method combining Water/ Oil/Water (W/O/W) emulsions with flow injection manifolds has been developed for determinations of Mg and Zn. The system consists of a mixing coil filled with Span 80 as a surfactant, palmitic acid or di(2-ethylhexyl) phosphate as an extractant, kerosene as a solvent in the oil phase, and HCl in the inner aqueous phase to form W/O emulsions, an extraction coil for the sample solution to form W/O/W emulsions, a phase separator to waste the outer aqueous phase, a dry bath to demulsify W/O emulsions with 2-ethylhexanol, a phase separator to waste the oil phase, and an air pump to deliver the concentrated sample solution to the flame atomic absorption spectrophotometer. This method proved to be excellent regarding the reproducibility, the rapidity, and the small quantity of sample, compared with the W/O/W emulsions method without the flow injection manifolds. The signal of flame atomic absorption spectrometry (FAAS) after preconcentration of Mg by this method was 2.4 times as large as that before preconcentration. Also, this method suppressed some interferences. The system was applied to FAAS determinations of Mg and Zn in duralumin alloys and Zn in commercial reagents.