A novel route for identifying starch diagenetic products in the archaeological record.

This work introduces a novel analytical chemistry method potentially applicable to the study of archaeological starch residues. The investigation involved the laboratory synthesis of model Maillard reaction mixtures and their analysis through Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS). Thus, starch from sixteen plant species were matured while reacting it with the amino acid glycine. The FTICR-MS analysis revealed > 5,300 molecular compounds, with numerous unique heteroatom rich compound classes, ranging from 20 (Zea mays) to 50 (Sorghum bicolor). These classes were investigated as repositories of chemical structure retaining source and process-specific character, linked back to botanical provenance. We discussed the Maillard reaction products thus generated, a possible pathway for the preservation of degraded starch, while also assessing diagenetic recalcitrance and adsorption potential to mineral surfaces. In some cases, hydrothermal experimentation on starches without glycine reveals that the chemical complexity of the starch itself is sufficient to produce some Maillard reaction products. The article concludes that FTICR-MS offers a new analytical window to characterize starchy residue and its diagenetic products, and is able to recognize taxonomic signals with the potential to persist in fossil contexts.

A rapid method to assess a broad inventory of organic species in marine sediments using ultra-high resolution mass spectrometry.

RATIONALE: A broad range of organic species in marine sediments is routinely used as biogeochemical proxies of Earth history. These species are typically analyzed using different analytical methods, targeting very specific components and often including time-intensive sample preparation. There is, therefore, a need for a more comprehensive, rapid and high-throughput approach to simultaneously analyze a broad range of known sedimentary polar species and also have a surveillance capability able to identify candidate new species classes. METHODS: Whole solvent extracts from recently deposited Gulf of Mexico marine sediments were obtained after a simple, one-step extraction. They were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), using atmospheric pressure photoionization in positive ion mode (APPI-P), over a broad mass range (m/z 150-1500). RESULTS: From 3000 to over 5000 peaks per sample were assigned molecular formulae, and the majority of assignments (90%) showed an absolute error lower than 200 ppb. The detected species belong to the NO1-7 , N4 O2-8 , O1-9 , HC, N and OS compound classes, including known biomarker species such as pigments (e.g. tetrapyrrole macrocycles and carotenoids) and lipids (e.g. glycerol dialkyl glycerol tetraethers, GDGTs), but also compounds of still unknown detailed molecular structure, but with clear potential geochemical relevance. CONCLUSIONS: The reported method enables rapid (12 min FTICR-MS analysis time) and simultaneous detection of a broad range of multi-heteroatom, polar organic species in whole sediment extracts. This allows for higher sample throughput, a more comprehensive investigation of sedimentary geochemistry, and potentially the discovery of new components and derivation of novel, multi-species proxies. Copyright © 2016 John Wiley & Sons, Ltd.

Rapid Screening of Glycerol Ether Lipid Biomarkers in Recent Marine Sediment Using Atmospheric Pressure Photoionization in Positive Mode Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Many of the molecular proxies commonly used for paleoenvironmental reconstruction are focused on a limited set of glycerol ether lipids, mainly due to the lack of more comprehensive analytical methods and instrumentation able to deal with a more diverse range of species. In this study, we describe an FTICR-MS-based method for rapid, nontargeted screening of ether lipid biomarkers in recent marine sediments. This method involves simplified sample preparation and enables rapid identification of known and novel ether lipid species. Using this method, we were able to identify complete series of core glycerol dialkyl glycerol tetraethers (GDGTs with 0 to 8 alicyclic rings), including the complete resolution of GDGT-4 and the unexpected detection of GDGTs with more than 5 rings, in sediments from mesophilic marine environments (sea surface temperature, SST, of 24-25 °C). Additionally, mono- and dihydroxy-GDGT analogs (including novel species with >2 rings), as well as glycerol dialkanol diethers, GDDs (including novel species with >5 rings) were detected. Finally, we putatively identified other, previously unreported groups of glycerol ether lipid species. Adequacy of the APPI-P FTICR-MS data for the determination of commonly used GDGT-based proxy indices was demonstrated. The results of this study show great potential for the use of FTICR-MS as both a rapid method for determining existing proxy indices and, perhaps more importantly, as a tool for the early detection of possible new biomarkers and proxies that may establish novel geochemical relationships between archaeal ether lipids and key environmental-, energy-, and climate-related system variables.

On-line desalting of crude oil in the source region of a Fourier transform ion cyclotron resonance mass spectrometer.

The presence of dissolved metal ions in waters associated with crude oils has many negative implications for the transport, processing, and refining of petroleum. In addition, mass spectrometric analysis of sodium containing crude oil samples suffers from ionization suppression, unwanted adduct formation, and an increase in the complexity of data analysis. Here, we describe a method for the reduction/elimination of these adverse effects by modification of the source region gas-inlet system of a 12 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Several acids were examined as part of this study, with the most suitable for on-line desalting found to have both high vapor pressure and low pK(a); 12.1 M HCl showed the strongest desalting effect for crude oil samples with a sodium removal index (SRI) of 88%-100% ± 7% for the NaOS compound class. In comparison, a SRI of only 38% ± 9% was observed for a H2O/toluene solution-phase extraction of oil 1. These results clearly demonstrate the increased efficacy of pseudo-vapor phase desalting with the additional advantages that initial sample solution conditions are preserved and no sample preparation is required prior to analysis.