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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