Determination of carboxylic SWCNTs in river water by microextraction in ionic liquid and determination by Raman spectroscopy

The paper proposes a simple approach for the preconcentration of carboxylated single-walled carbon nanotubes and their determination in river water samples. The method is based on a microliquid–liquid extraction into an ionic liquid (bmim PF6) in the presence of a cationic surfactant (CTAC). 10 μL of the ionic liquid phase are microfiltrated by using a home-made filtration device having a small diameter. The membrane was of cellulose with a pore size of 5 μm. Finally, the carbon nanotubes retained in the membrane are directly analyzed by Raman spectroscopy, which allows their direct characterization and quantification. The limit of detection was 0.050 mg L−1. The precision, for a 1.4 mg L−1 concentration of carbon nanotubes, is 3.2%.