Spectral characterisation of eight glycerolipids and their detection in natural samples using time‐of‐flight secondary ion mass spectrometry

Abstract

In recent years, time-of-flight secondary ion mass spectrometry (ToF-SIMS) with cluster ion sources has opened new perspectives for the analysis of lipid biomarkers in geobiology and organic geochemistry. However, published ToF-SIMS reference spectra of relevant compounds are still sparse, and the influence of the chemical environment (matrix) on the ionisation of molecules and their fragmentation is still not well explored. This study presents ToF-SIMS spectra of eight glycerolipids as common target compounds in biomarker studies, namely ester- and ether-bound phosphatidylethanolamine, ester- and ether-bound phosphatidylcholine, ester-bound phosphatidylglycerol, ester- and ether-bound diglycerides and archaeol, obtained with a Bi(3) (+) cluster ion source. For all of these compounds, the spectra obtained in positive and negative analytical modes showed characteristic fragments that could clearly be assigned to e.g. molecular ions, functional groups and alkyl chains. By comparison with the reference spectra, it was possible to track some of these lipids in a pre-characterised organic extract and in cryosections of microbial mats. The results highlight the potential of ToF-SIMS for the laterally resolved analysis of organic biomarkers in environmental materials. The identification of the target compounds, however, may be hampered by matrix effects (e.g. adduct formation) and often require careful consideration of all spectral features and taking advantage of the molecular imaging capability of ToF-SIMS.

Exposing latent fingermarks on problematic metal surfaces using time of flight secondary ion mass spectroscopy

“…However, the signal intensities were much weaker in comparison to the strong signals obtained from the inorganic Na + and K + ions present in the predominantly eccrine fingermark residues (Figure 3). The negative ion spectra of the fingermarks also contained evidence of additional secondary ions that are consistent with the presence of lipids such as the phosphite ion (PO3 -) observed at m/z 78.96 [45]. Figure 5 are photographs of the same sample that was removed from the ToF-SIMS chamber, fumed using CNA and stained using the three dyes, BY40, CV, and SB according to the protocol described previously.…”

“…Dihydrogen phosphate (H2PO4 -) ions were also detected in the fingermark residue. The presence of these ions is most likely due to the presence of trace amounts of phospholipid in the fingermarks [45]. An additional high molecular weight ion (C12H25SO4 -), was also observed.…”

Extreme 13C depletion of carbonates formed during oxidation of biogenic methane in fractured granite

“…ToF-SIMS analyses of single calcite grains and organic extracts were conducted using a ToF-SIMS IV (ION-TOF GmbH, with liquid bismuth cluster ion source; settings in ref. 65 ). Compounds and corresponding characteristic fragments detected with ToF-SIMS and GC/MS within the AOM calcites are listed in Supplementary Table 4 .…”

Cellular metabolic profiling using ToF‐SIMS

“…Alternatively, when the sample is large, as is the case with tissues, cryo‐sections can be prepared and imaged (Fig. ).…”