SPE Offers Multiple Advantages Over LCC for Hydrocarbon Analysis by GC–MS

A study from Aramco Americas and Saudi Aramco has compared solid-phase extraction (SPE) to traditional normal-phase liquid column chromatography (LCC) methods for the analysis of hydrocarbons by gas chromatography–mass spectrometry (GC–MS) (1). The team compared five different sorbents to assess their efficiency in hydrocarbon fractionation. The study was published in the Journal of Chromatography A.

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Hydrocarbons are organic compounds and are found in crude oil, natural gas, and coal. Serving as fuels and lubricants, their complex matrices necessitate meticulous sample preparation to ensure effective separation of saturate and aromatic fractions. Traditional normal-phase LCC methods are labor-intensive and require a large amount of solvents, so the team decided to determine if SPE would be a better, more environmentally friendly alternative for the analysis.SPE is the most used technique for extracting, solvent exchanging, purifying, concentrating, and fractionating organic compounds from various samples (2).

The study tested five sorbents: neutral silica (Si), SiOH, neutral alumina (Al), Ag-ion, and Ag-ion mixed with activated silica. The key metrics for evaluation included peak resolution, compound recovery, and isomer ratios—critical parameters for assessing thermal maturity and depositional environments.

There was significant variability in separation efficiency among the sorbents tested. SiOH, neutral Si, and neutral Al exhibited poor separation of aromatics from saturates. Up to 100% of aromatics remained in the saturate fraction, compromising the accuracy of geochemical interpretations. Ag-ion showed improved aromatic separation but still allowed partial coelution. Ag-ion mixed with activated silica provided the best separation, enhancing aromatic compound recovery by up to 23 times compared to SiOH. This combination proved to be the most reliable for quantifying both saturate and aromatic fractions. The team stressed how their findings emphasize the importance of sorbent selection in SPE methodologies. The Ag-ion/activated silica combination achieved superior resolution, reducing matrix interference and ensuring more accurate GC–MS analysis of hydrocarbon fractions.

A notable advantage of SPE over LCC is the substantial reduction in solvent consumption. There was a 63% decrease in solvent use when employing SPE, which aligns with growing industry efforts to adopt greener laboratory practices. Given the known toxicity of common LC solvents such as dichloromethane—a category 2 carcinogen—reducing the volume of harmful chemicals used during sample processing is essential (1).

According to the team, this study validates the application of SPE as a viable alternative to LCC for hydrocarbon analysis via GC–MS. The Ag-ion/activated silica sorbent combination emerged as the most effective, providing enhanced resolution, higher recovery rates, and reduced solvent usage. The method offered a “more sustainable approach to hydrocarbon analysis” (1). As scientists and chromatographers seek more efficient and sustainable techniques, adopting optimized SPE methods can significantly improve analytical workflows in petroleum and environmental research. Future studies may further refine SPE methodologies, exploring additional sorbents and elution conditions to expand their applicability in complex sample matrices.

References

(1) Srinivasan, P.; Arguello, E. M. E.; Atwah, I. Evaluating the Reliability of Solid Phase Extraction Techniques for Hydrocarbon Analysis by GC–MS. J. Chrom A 2024, 1737, 465435. DOI: 10.1016/j.chroma.2024.465435

(2) Andrade-Eiroa, A.; Canle, M.; Leroy-Cancellieri, V.; Cerdà, V. Solid-phase Extraction of Organic Compounds: A Critical Review (Part I). TrAC 2016, 80, 641–654. DOI: 10.1016/j.trac.2015.08.015