An Introduction to Gas Chromatography: Applications, Instrumentation and Data Analysis

Gas chromatography (GC) is a widely used technique for separating and analyzing mixtures of chemical compounds. By vaporizing the analytes and carrying them through a column with an inert carrier gas, GC is able to effectively separate compounds based on differences in their partitioning between the stationary and mobile phases. This separation capability, combined with highly sensitive detection methods, enables GC to detect analytes at trace levels and identify unknown components in complex samples. In this article, we will explore the basic principles of gas chromatography, common applications, instrumentation components, data analysis, and emerging multidimensional techniques expanding GC’s separation power.

Applications of Gas Chromatography

  • Quality control and analysis of products in industries like automotive, chemicals, petrochemicals and pharmaceuticals.

  • Environmental monitoring of air, water and soil for pollutants, microplastics and other contaminants.

  • Analysis of petroleum and petroleum products like gasoline.

  • Forensic analysis of drugs, explosives and other substances.

  • Natural products isolation and identification from plants, foods and other sources.

  • Diagnostics and clinical analysis, e.g. analyzing lipids and sterols.

  • Metabolomics research to study biological processes.

  • GC is also commonly coupled with mass spectrometry (GC-MS) to facilitate compound identification. Advances in multidimensional GC are helping analyze increasingly complex samples. Recent studies have used GCxGC-(TOF)-MS to identify over 400 volatile organic compounds (VOCs) linked to Covid-19 infection.

    Instrumentation Components of Gas Chromatography

  • Carrier gas – an inert gas like helium or hydrogen that transports the vaporized sample through the instrument.

  • Inlet – where the sample is introduced and vaporized before entering the column.

  • Analytical column – a long capillary tube coated with a stationary phase for chromatographic separation.

  • Oven – houses and heats the column to optimal temperatures during analysis.

  • Detector – measures a physical property of eluting analytes to generate a signal response.

  • Data system – records and processes the detector response over time into a chromatogram.

  • How Gas Chromatography Works

  • Sample is injected into the inlet, vaporized and carried by the mobile phase gas through the column.

  • Analytes partition between the stationary and mobile phases, separating based on differences in this distribution.

  • Less retained analytes elute from the column first, followed by more retained compounds.

  • Separated analytes exit the column and are detected, generating peaks in the chromatogram.

  • Retention time identifies compounds, peak areas relate to concentration.

  • Reading and Interpreting Chromatograms

  • X-axis is retention time from sample injection to run end.

  • Y-axis is detector response, related to analyte concentration.

  • Peaks identify separated analytes, with retention time and area/height data.

  • Peak shapes, widths, resolution and baselines provide method/system info.

  • Chromatograms are analyzed using integration software.

  • Advanced Techniques: Two-dimensional Gas Chromatography

  • GCxGC uses two columns of differing polarity for comprehensive separation.

  • Modulator interfaces columns, taking narrow cuts for 2D separation every 1-10 seconds.

  • Provides higher peak capacity for analyzing complex real-world samples.

  • Commonly used with petroleum, environmental, food, fragrance and metabolomics samples.

  • Enables identification of hundreds to thousands of compounds from single analyses.

  • Conclusions

    Gas chromatography is a highly versatile analytical technique employed across many industries and research fields. Recent advances like multidimensional GC are helping to unlock ever more complex samples. New areas of application continue to emerge as well, such as using GC and GC-MS to study microbial volatile organic compounds and their potential use as disease biomarkers. Overall, GC’s high sensitivity, resolution, reliability and compatibility with numerous detection methods ensure it will remain a key player in chemical analysis for years to come.

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