Sequential Preconcentration and On-Membrane Raman Determination of Carboxylic Single-Walled Carbon Nanotubes in River Water Samples

This article proposes a simple and sensitive approach for the preconcentration and determination of carboxylated single-walled carbon nanotubes (c-SWNTs) in environmental samples using membranes modified with multiwalled carbon nanotubes (MWNTs). The method is based on the preconcentration of c-SWNTs and their direct on-filter Raman spectroscopic analysis. The preconcentration of c-SWNTs is performed by microfiltrating the sample through a cellulose membrane modified with MWNTs fabricated from a surfactant dispersion of the same. The analytes are retained in the membrane through π–π interactions with MWNTs forming the membrane. The G-/D-band ratio of the carbon nanotubes has been used as an analytical parameter to quantify the presence of c-SWNTs, which mainly contribute to the intensity of the G band. The limit of detection was found to be 1 μg·L–1, and the precision, for a 10 μg·L–1 concentration of c-SWNTs, was 4.74% intramembrane and 6.3% intermembrane. The optimized procedure was successfully applied to the determination of traces of c-SWNTs in river water samples.