A Review on Pretreatment Method for the Analysis of Complex Chemical Composition of Resinite

The separation, detection, and analysis of complex organic compositions in fossil resin have always been a hot and difficult point in the research. The early sample pretreatment methods and the separation and analysis efficiency of one-dimensional gas chromatography-mass spectrometry (1D GC-MS) were limited, overlapping spectral peaks and missing mass spectra peaks of trace substances easily occurred in the chromatography-mass spectrometry analysis, .Hence, it was difficult to accurately identify its chemical compositions. In this review, it systematically summarizes the application, advantages, and disadvantages of four pretreatment methods (solvent extraction, chemical derivatization, pyrolysis, and solid phase microextraction) used in the compositions analysis of resinites. (1)Solvent extraction is suitable for the analysis of sesquiterpenes, triterpenes, phenols, saturated hydrocarbons, aromatic hydrocarbons, and other substances in the resin fossils. However, amber with high degree of petrifaction requires a long time to dissolve and cannot be completely dissolved, hence, solvent extraction is much more applicable to copal with lower degree rather than highly fossilized amber. (2)Chemical derivatization is applicable to qualitative analysis of molecules with active hydrogen in the group, which can effectively improve the volatility and stability of related molecules and enhance the response signal intensity after derivatization. (3)Thermal pyrolysis mainly aims at the analysis of the main macromolecular skeleton of the resinite, but there will be some deviation in the reduction of the initial structure by the pyrolysates. (4)Solid phase microextraction is suitable for the analysis of volatile/semi-volatile components in amber, but it is prone to incomplete detection. The sample pretreatment technologies of headspace high-capacity solid phase microextraction and direct thermal desorption combining with comprehensive two-dimensional gas chromatography and mass spectrometry (GC-MS) were creatively proposed, which could detect 3-4 times as many compounds number as the traditional analysis method. More representative biomarkers can be screened by untargeted metabolomics strategies to analyze the GC-MS results of resinites from different habitats. Our team will focus on the isolation of complex organic components and the accurate identification of isomers, and reveal the origin of ancient plants and genesis of resin fossils of different origins and ages. It is expected to solve the outstanding problems in the detection and analysis of complex organic components in the solid phase, and efficiently analyze volatile and semi volatile organic compounds in terms of separation, secondary enrichment, and screening of highly specific biomarkers, which provides a theoretical and technical foundation for the exploration of reconstruction of their palaeoecological environment and maturation evolution.