Separation of Silver Nanoparticles with Different Coatings by Capillary Electrophoresis Coupled to ICP-MS in Single Particle Mode

The possibility of separating mixtures of Ag nanoparticles (NPs) with similar sizes but different surface coatings using capillary electrophoresis coupled to single particle inductively coupled mass-spectrometry (CE-SP-ICP-MS) was investigated. In two-component mixtures, it was possible to separate 40 nm sized polyvinylpirrolidone (PVP)- and citrate-coated NPs, 40 nm sized polyethylene glycol (PEG)- and citrate-coated NPs, and 60 nm sized PVP- and citrate-coated NPs. The separation of a more complex mixture containing NPs with the different coatings and sizes was successful, and each component, namely, 20, 40, and 60 nm sized citrate-coated and 40 and 60 nm sized PVP-coated NPs, could be distinguished. The theoretically expected migration order was confirmed by experimental results with selected Ag NPs. On the basis of the experimental observations, a separation mechanism that considers the effect of stable vs displaceable coatings during NP migration in CE is suggested. The ICP-MS was equipped with a prototype data acquisition system (μsDAQ) that provided 5 μs time resolution.