Miniaturized liquid chromatography coupled on-line to in-tube solid-phase microextraction for characterization of metallic nanoparticles using plasmonic measurements. A tutorial.

This tutorial aims at providing guidelines for analyzing metallic nanoparticles (NPs) and their dispersions by using methods based on miniaturized liquid chromatography with diode array detection (MinLC-DAD) and coupled on-line to in-tube solid-phase microextraction (IT-SPME). Some practical advice and considerations are given for obtaining reliable results. In addition, this work outlines the potential applications that set these methodologies apart from microscopy-related techniques, dynamic light scattering, single particle ICP-MS, capillary electrophoresis, field-flow fractionation and other chromatographic configurations, which are discussed and mainly seek to accomplish size estimation and NP separation, speciation analysis and quantification of mainly AgNPs and AuNPs. MinLC-DAD has the potential to estimate the NP concentration and from it the average size of unknown samples by calibrating with a single standard, as well as studying potentially non-spherical particles and stability-related properties of their dispersions. While keeping the signal dependency with concentration and increasing the method sensitivity, IT-SPME-MinLC-DAD goes further allowing for the assessment of the dispersant effect and ultimately changes in the nanoparticle surroundings that range from modifications of the hydrodynamic diameter to the exposure to different reagents and matrices. The methodology can still be improved by either exploring newer IT-SPME adsorbents or by assaying new system configurations. Taking into account that this technique gives complementary information in relation to other techniques discussed here, this tutorial serves as a guide for analyzing metallic NPs towards a better understanding of the particle behavior under different scenarios.