Technical principles and application progress of gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry (GC-MS) is one of the widely used instruments in modern analytical chemistry. It combines the efficient separation capability of gas chromatography (GC) with the high sensitivity and selectivity detection function of mass spectrometry (MS), achieving qualitative and quantitative analysis of various components in complex mixtures. It is widely used in fields such as environmental monitoring, food safety, drug analysis, forensic identification, petrochemicals, and life science research.

1、 Technical principles

The gas chromatography-mass spectrometer mainly consists of three parts: gas chromatography unit, interface system, and mass spectrometer detector.

1. Gas chromatography (GC) section

Gas chromatography is responsible for the separation of various components in the sample. After vaporization, the sample is pushed through a long and thin chromatographic column by an inert carrier gas (such as helium or nitrogen). Different compounds have varying migration speeds in the column due to their different distribution coefficients between the stationary and mobile phases, thus achieving separation. The commonly used chromatographic column is a capillary column, which has high separation efficiency and good reproducibility.

2. Interface system

Due to the fact that GC operates at atmospheric pressure while MS needs to operate in a high vacuum environment, an efficient "interface" must be used to connect the two. The most common type is the direct import interface, which directly inserts the end of the chromatographic column into the mass spectrometry ion source to ensure that the separated components quickly enter the mass spectrometry system, avoiding diffusion or condensation.

3. Mass spectrometry (MS) detection section

The molecules entering the mass spectrum are first bombarded by a high-energy electron beam in an electron impact ionization (EI) source, losing electrons to form positively charged molecular ions, and further fragmented into characteristic fragment ions. These ions are separated by a mass analyzer (commonly a quadrupole or time-of-flight TOF) according to the mass to charge ratio (m/z), and the signal intensity is recorded by a detector. Finally generate a mass spectrum, providing molecular weight and structural information of the compound.

Standard databases, such as the NIST library, can automatically match mass spectra of unknown substances for rapid qualitative analysis.

2、 Advantages of gas chromatography-mass spectrometry technology:

-High sensitivity: capable of detecting trace substances at ppb (parts per billion) or even ppt (parts per trillion) levels.

-High selectivity: Even co elution peaks can be distinguished by mass spectrometry.

-Qualitative accuracy: Based on standard spectral library matching, the qualitative results are reliable.

-High degree of automation: supports automatic sampling, data collection and processing, suitable for large-scale sample analysis.

3、 Main application areas

1. Environmental monitoring: used to detect pollutants such as volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), pesticide residues, etc. in the air, water, and soil.

2. Food safety: Screening for additives, plasticizers, pesticide residues, and illegal additives in food.

3. Forensic toxicology: Quickly identify small molecule substances in blood or urine in poisoning cases.

4. Metabolomics research: Combining derivatization techniques to analyze small molecule metabolites in biological samples and reveal disease mechanisms.

5. Petrochemical industry: used for oil composition analysis, cracking product identification, etc.

As one of the "gold standard" tools for analytical science, gas chromatography-mass spectrometry continues to play a key role in scientific research and industry due to its separation and identification capabilities. With continuous technological innovation, GC-MS will demonstrate broader application prospects in precision analysis, real-time monitoring, and interdisciplinary research.