Chromatographic Reduction of Isobaric and Isomeric Complexity of Fulvic Acids To Enable Multistage Tandem Mass Spectral Characterization

Abstract

Humic substances and related material commonly grouped under the designation of natural organic matter (NOM) are of interest in fields ranging from marine chemistry and geochemistry to industry, agriculture, and pharmacology. High-field Fourier transform ion cyclotron resonance mass spectrometry enables resolution and identification of elemental compositions of up to thousands of components from a single mass spectrum. Here, we introduce an offline prefractionation to reduce the number of species of the same nominal (nearest-integer) mass, allowing for isolation of ions of one or a few m/z values, from which structural information can be obtained by low-resolution multistage tandem mass spectrometry (MS(n)). Alternatively, precharacterized fractions can be generated for other types of analysis. As an example, we demonstrate significant reduction of isomeric and isobaric complexity for Suwannee River fulvic acid (SRFA). The combined MS and MS(n) analyses support the hypothesis that early eluting material comprises older, highly oxidized SRFA, whereas later eluting material is younger, retaining some similarity with precursor material.

Extreme isomeric complexity of dissolved organic matter found across aquatic environments

“…Alternatively, our results may be explained by similar functional group chemistry of the various structural isomers leading to similar fragmentation patterns, and chemical differences that lead to the polarity distribution being present on the carbon backbone (Capley et al 2010). This issue is difficult to resolve with our online technique.…”

“…The more apolar, oxygen poor precursor ions required more energy to fragment (Capley et al 2010), leading to a higher relative intensity of precursor peak remaining after fragmentation at a given energy (Fig. 3).…”

Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter

“…1 Key to a greater understanding of the complex system of biogeochemical processes involved in the formation and removal of DOM is an understanding of the exact nature of DOM itself. 22,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] The above functional groups are found within major classes of compounds, such as amino acids, proteins, peptides, sugars, amino-sugars, carboxylic rich alicyclic molecules (CRAM), materials derived from linear terpenoids (MDLT), neutral lipids, DNA, RNA, and sterols. 1 shows the research papers published annually based upon an article title search (Scopus) using the term 'dissolved organic matter').…”

“…humic or fulvic acids). 34,35,[159][160][161] As most of the MS and MS n experiments are difficult to interpret, particularly identifying isobaric losses and the rearrangements that can occur during fragmentation, tools such as H/D exchange can help to distinguish functional groups such as hydroxyls from ethers or carbonyls. However, despite MS detection providing an additional dimension in achievable resolution, it should be noted that challenges remain in the interpretation of the resulting spectra which are characterised by multitudes of molecular adducts or ions derived from the thousands of compounds characterising DOM.…”

Analysis of the Volatile Compounds in Senecio Scandens Buch-Ham by Gas Chromatography—Tandem Mass Spectrometry Based on Diversified Scan Technologies

“…5 tandem mass spectrometry (MS/MS) technology is an important tool to confirm the elemental composition of compounds and distinguish isomers and isobars. [6][7][8][9] the elemental composition of compounds could be confirmed by high-resolution mass spectrometry, 1,10,11 while they could also be confirmed by exploiting the tandem mass spectra of isotopic peaks from the precursor ion. 11 the product ion scan supplied the fragmentation information of the precursor ion, 6,[12][13][14] which can be used for the discrimination of parent ions with the same molecular weight and reducing the false matching rate.…”