Gas Chromatography Coupled to High Resolution Time-of-Flight Mass Spectrometry as a High-Throughput Tool for Characterizing Geochemical Biomarkers in Sediments

Hector Henrique Ferreira Koolen; Clécio Fernando Klitzke; Joe Binkley; Jeffrey Patrick; Ana Cecília Rizatti de Albergaria-Barbosa; Rolf Roland Weber; Márcia Caruso Bícego; Marcos Nogueira Eberlin; Giovana Anceski Bataglion

doi:10.1155/2018/2560498

Gas Chromatography Coupled to High Resolution Time-of-Flight Mass Spectrometry as a High-Throughput Tool for Characterizing Geochemical Biomarkers in Sediments

Int J Anal Chem. 2018 Dec 2:2018:2560498. doi: 10.1155/2018/2560498. eCollection 2018.

Affiliations

¹ ThoMSon Mass Spectrometry Laboratory, Institute of Chemistry, University of Campinas (UNICAMP), 13083-970, Campinas, SP, Brazil.
² Metabolomics and Mass Spectrometry Research Group, Amazonas State University (UEA), 69065-001, Manaus, AM, Brazil.
³ LECO Corporation, 49085, St. Joseph, MI, USA.
⁴ Laboratory of Marine Geochemistry, Geoscience Institute, Federal University of Bahia (UFBA), 40170-020, Salvador, BA, Brazil.
⁵ Marine Organic Chemistry Laboratory, Oceanographic Institute, University of São Paulo (USP), 05508-120, São Paulo, SP, Brazil.
⁶ Department of Chemistry, Federal University of Amazonas (UFAM), 69077-000, Manaus, AM, Brazil.

Abstract

The performance of gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC-HRTofMS) for characterizing geochemical biomarkers from sediment samples was evaluated. Two approaches to obtain the geochemical biomarkers were tested: (1) extraction with organic solvent and subsequent derivatization and (2) in-situ derivatization thermal desorption. Results demonstrated that both approaches can be conveniently applied for simultaneous characterization of many geochemical biomarkers (alkanes, alkanols, sterols, and fatty acids), avoiding conventional time-consuming purification procedures. GC-HRTofMS reduces both sample preparation time and the number of chromatographic runs compared to traditional methodologies used in organic geochemistry. Particularly, the approach based on in-situ derivatization thermal desorption represents a very simple method that can be performed in-line employing few milligrams of sediment, eliminating the need for any sample preparation and solvent use. The high resolving power (m/Δm _50% 25,000) and high mass accuracy (error ≤ 1 ppm) offered by the "zig-zag" time-of-flight analyzer were indispensable to resolve the complexity of the total ion chromatograms, representing a high-throughput tool. Extracted ion chromatograms using exact m/z were useful to eliminate many isobaric interferences and to increase significantly the signal to noise ratio. Characteristic fragment ions allowed the identification of homologous series, such as alkanes, alkanols, fatty acids, and sterols. Polycyclic aromatic hydrocarbons were also identified in the samples by their molecular ions. The characterization of geochemical biomarkers along a sedimentary core collected in the area of Valo Grande Channel (Cananéia-Iguape Estuarine-Lagunar System (São Paulo, Brazil)) provided evidences of environmental changes. Sediments deposited before opening of channel showed dominance of biomarkers from mangrove vegetation, whereas sediments of the pos-opening period showed an increase of biomarkers from aquatic macrophyte (an invasive vegetation).