Ultratrace determination of silver, gold, and iron oxide nanoparticles by micelle mediated preconcentration/selective back-extraction coupled with flow injection chemiluminescence detection.

A new method has been developed for the ultrasensitive determination of silver, gold, and iron oxide nanoparticles in environmental samples. Cloud point extraction was optimized and used as a means to extract and preconcentrate all nanoparticle species simultaneously from the same sample. The extracted nanoparticles were sequentially isolated from the surfactant-rich phase by a new selective back-extraction procedure and dissociated into their precursor metal ions. Each ion solution was injected in a flow injection analysis (FIA) manifold, accommodating the chemiluminogenic oxidation of luminol, in order to amplify chemiluminescence (CL) emission in a manner proportional to its concentration. Under the optimum experimental conditions, the detection limits were brought down to the picomolar and femtomolar concentration levels with satisfactory analytical features in terms of precision (2.0-13.0%), selectivity against dissolved ions, and recoveries (74-114%). The method was successfully applied to the determination of iron oxide, silver, and gold nanoparticles in environmental samples of different complexity, ranging from unpolluted river water to raw sewage. The developed method could also serve as a basis for future deployment of molecular spectrometry detectors for the selective determination and speciation analysis of nanoparticles in environmental applications.