Assessment of the removal of side nanoparticulated populations generated during one-pot synthesis by asymmetric flow field-flow fractionation coupled to elemental mass spectrometry

•AF4 allows the efficient separation of nanoparticle populations of similar sizes.•Chemical identification of different nano-sized species in complex mixtures achieved.•The DHLA surface-capping procedure directly produces purified QDs.

Coupling of asymmetric flow field-flow fractionation (AF4) to an on-line elemental detection (inductively coupled plasma-mass spectrometry, ICP-MS) has been recently proposed as a powerful diagnostic tool for characterization of the bioconjugation of CdSe/ZnS core-shell Quantum Dots (QDs) to antibodies. Such approach has been used herein to demonstrate that cap exchange of the native hydrophobic shell of core/shell QDs with the bidentate dihydrolipoic acid ligands directly removes completely the eventual side nanoparticulated populations generated during simple one-pot synthesis, which can ruin the subsequent final bioapplication. The critical assessment of the chemical and physical purity of the surface-modified QDs achieved allows to explain the transmission electron microscopy findings obtained for the different nanoparticle surface modification assayed.