# Deciphering the binding strength of oil matrix through molecularly resolved release energy analysis using thermal slicing ramped pyrolysis GC-MS

## TL;DR

This paper introduces a new method to study how tightly compounds are bound in oil using advanced thermal analysis and mass spectrometry.

## Contribution

The novel approach combines thermal slicing ramped pyrolysis GC-MS with release energy analysis to link molecular structures to energetic characteristics in petroleum.

## Key findings

- Photodegradation increases the energy required to release n-alkanes from ca. 90 kJ/mol to over 100 kJ/mol.
- Tarball samples showed higher n-alkane release energy (118 kJ/mol) compared to crude oil (110 kJ/mol).
- The matrix strength of n-alkanes in tarballs shows a homogenizing trend.

## Abstract

Recent advancements in analytical techniques have significantly furthered our understanding of the chemical composition of petroleum and its derivatives. However, there remains a missing link connecting the molecular structure with how specific compounds are bound within the sample matrix. Traditional approaches to study energetic characteristics of petroleum often rely on bulk property measurements (e.g., thermogravimetric analysis), therefore lacking the resolution needed to capture compound-specific interactions and structural information. In this work, we aim to fill the gap between compositional and energetic analyses by employing thermal slicing ramped pyrolysis gas chromatography mass spectrometry (TSRP-GC-MS). TSRP-GC-MS enables the analysis of temperature-dependent release patterns of pyrolyzates, linking molecular structures to energetic characteristics via computing the energy distributions for specific pyrolyzates. Results of the photodegradation experiments demonstrate that as the photodegradation proceeds, the energy required to disrupt the matrix and to release n-alkanes increased from ca. 90 kJ/mol to over 100 kJ/mol, with significant increases for each individual n-alkane. The release energy of individual n-alkanes in crude oil and in tarball collected in the field were further compared in the second case study. The results not only showed an increase from 110 kJ/mol for n-alkanes in crude oil to 118 kJ/mol in tarball, but also revealed a homogenizing trend of the matrix strength of different n-alkanes in the latter. Overall, the proposed TSRP-GC–MS approach offers a powerful tool for advancing our understanding of petroleum and oil and has the potential to be expanded to the study of other complex natural mixtures.

The online version contains supplementary material available at 10.1007/s00216-025-06110-9.