Proposed guidelines for sample preparation and ESI-MS analysis of humic substances to avoid self-esterification

Cameron McIntyre, Christopher McRae*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    26 Citations (Scopus)

    Abstract

    Standard humic substances (HS) were stored in 13C-labelled methanol, ethanol, 2-propanol and d3-methanol to investigate whether they underwent self-esterification with the solvents or not. Data from stable carbon isotope analysis, 13C NMR spectroscopy and electrospray ionisation mass spectrometry (ESI-MS) showed that significant self-esterification of carboxyl groups began immediately after dissolution. The major implication is that data collected in previous studies using these solvents in conjunction with HS are likely to be compromised. Self-esterification was minimised by varying parameters such as % water, temperature, concentration, storage time and buffer. Solvent reactivity was found to be: ethanol > 2-propanol > methanol. The study proposes preliminary guidelines for the preparation and storage of HS and their analysis by ESI-MS. The primary recommendation is to avoid the use of these solvents and use alternatives such as acetonitrile and water.

    Original languageEnglish
    Pages (from-to)543-553
    Number of pages11
    JournalOrganic Geochemistry
    Volume36
    Issue number4
    DOIs
    Publication statusPublished - Apr 2005

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