Fullerenes are an important class of chemicals used in solar cell production, and they can also be formed during combustion processes.
When fullerene molecules of around 1 nm in size are present in the environment, they tend to form water stable aggregates or clusters of different sizes, based on the water matrix and temperature.
Information on these clusters is very important as the behavior of these clusters in the environment (adsorption, diffusion, degradability) and their toxicology are strongly influenced by their size. Until now, these clusters have been separated using field-flow fractionation techniques.
However, the identification of the cluster components using high resolution mass spectrometry was only possible offline until now. The setup described in this article enables online coupling of an asymmetrical flow FFF system to an Orbitrap HRMS.
Toluene Dopant Device and FFF Connection
It is necessary to introduce toluene for optimal ionization of fullerenes in an APPI chamber. A dopant device needs to be built to add the toluene to the auxiliary gas, as toluene cannot be added to the water phase due to immiscibility.
A HPLC pump that carries the toluene should be connected to the auxiliary gas tube using a “T”- junction. This allows the toluene to be transported to the ionization chamber with the auxiliary gas stream. The outlet stream of the FFF is directly coupled to the inlet port of the APPI probe.
Figure 1. Graphical illustration of the FFF-MS principle. The fractograms are obtained from an actual measurement by Herrero et al1
- Postnova Analytics AF2000 Asymmetric Flow FFF System
- Thermo Scientific Orbitrap HRMS
- Thermo Scientific APPI interface
- HPLC pump for the toluene
Find Out More About the System Settings
This work demonstrates that Flow FFF can be coupled online to an Orbitrap HRMS with an APPI chamber. With this setup, fullerene clusters can be directly identified in aqueous matrices after the particles have been separated using Asymmetrical Flow FFF.
As a result, this setup enables the characterization of fullerene clusters with non-destructive analytical techniques such as MALS or UV-Vis and subsequent identification of the mass of the compounds present in these clusters. Until now, this had been achieved by collecting separate fractions.
References and Further Reading
- P. Herrero, P.S. Bäuerlein, E. Emke, E. Pocurull, P. Voogt, J. Chromatogr. A, 2014, 1356, 277-282.
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