Graphene oxide structure affects mass spectra of small molecules

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  • Published: Apr 25, 2015
  • Author: Steve Down
  • Channels: X-ray Spectrometry / Base Peak / UV/Vis Spectroscopy / Raman / NMR Knowledge Base / Chemometrics & Informatics / Infrared Spectroscopy / Atomic / Proteomics / MRI Spectroscopy

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The laser desorption/ionisation mass spectra of small molecules like amino acids and sugars are influenced by the type of graphene oxide used as the substrate.

LDI MS has been used extensively for the analysis of large molecules but the typical matrices used to support the test compounds are unsuitable for the analysis of small molecules. The matrix adduct ions produced under ionisation appear in the same low-mass region of the spectra as those from the analytes, causing notable interference.

Graphene oxide has been proposed as an alternative matrix for small molecules. It has advantageous properties such as efficient energy transfer, good water dispersibility and the ability to be shaped but which type of graphene oxide is the most suitable? Scientists from Seoul National University have attempted to find out.

Writing in Chemistry - A European Journal, Dal-Hee Min and Young-Kwan Kim described how they compared large and small graphene oxide sheets and nano-seized graphene oxide. Under LDI in the absence of analytes, the large sheets produced many fragments, probably due to the abundance of oriented epoxy groups. The small sheets showed less fragmentation with nano graphene oxide the most stable. The fewer the fragments from graphene oxide, the clearer the spectra of the target compounds.

This was illustrated for the analysis of compounds like amino acids, peptides and saccharides, nano graphene oxide giving the lowest background signal while maintaining good energy transfer to the target molecules. The tricky analysis of the hydrophobic pollutants benzo[a]pyrene and benzoyldibenzo-p-dioxin was also achieved without any special separation or enrichment processes and without surface modification, however the latter could be introduced to improve sensitivity and selectivity.

These results will be useful for developing LDI MS methods for small molecules using graphene oxide as a matrix material.

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