Gas Chromatography Mass Spectrometry (GC-MS)
What is GCMS?
Gas Chromatography Mass Spectrometry (GC-MS) is an analytical technique with combines the two powerful techniques of gas chromatography (GC) and mass spectrometry (MS), to analyze the compounds present within complex chemical mixtures.
In the process, the mass spectrometer functions as a detector that identifies and quantifies the vaporized compounds separated during GC. While gas chromatography with other detector technologies provides data regarding retention time and peak intensity, mass spectrometry introduces and additional dimension: mass data/information. This mass information facilitates the identification, quantification, and understanding of the structural and chemical attributes of molecules.
The distinctive benefit of GC-MS is its information-rich detection capability with qualification and quantification abilities, enabling the detection of components even at exceedingly low concentrations. This makes it the preferred technique for many regulatory assessments and quality control procedures. Moreover, it’s a robust instrument for impurity analysis, offering detailed molecular characterisation at trace levels across various types of samples.
The GC-MS Analysis Process:
- The analysis begins with the sample undergoing vaporisation within the injector of the gas chromatograph, where it is transformed into the gas phase and separated into its various components using a capillary column coated with a stationary phase.
- An inert carrier gas (mostly helium for GC-MS) then propels these compounds through the system.
- While traveling through the column, the vaporized compounds interact with the stationary phase, each compound travelling at varied speeds depending on its unique chemical properties. Ultimately, leading to their separation before being transferred to the mass spectrometer.
- Upon introduction into the mass spectrometer, the compounds undergo ionization in an ion source, where they neutral molecules eluting from the GC column become ions.
- There are two types of ionization used commonly in GC-MS, Electron Ionization (EI) and Chemical Ionization (CI). Electron ionisation is the most common form of ionization, in which the molecules from the sample are ionized and often fragmented through collisions with high-energy electrons to generate ions with specific masses.
- Those newly created ions are separated in the Mass Analyzer based on their mass-to-charge ratio(m/z)
- Subsequently, the ions reach the Mass Spectrometry detector, where the ions are measured and the mass-to-charge ratio (m/z) and relative abundance (the quantity of each fragment present in the sample) are calculated.
- The mass spectrometer produces a mass spectrum illustrating the signal intensity or abundance corresponding to each detected fragments mass-to-charge ratio. The m/z ratios of the intact and fragment ions serve as a distinct “fingerprint” of the molecule aiding in chemical identification.
- Comparing EI mass spectra obtained by 70ev with available mass spectra libraries facilitates the process of identifying and quantifying unknown compounds and target analytes in the analysis as the fingerprint of ions is comparable even from different instruments
Industries requiring the use of GC-MS include:
- In forensic investigations, GC-MS is used to analyse suspect chemical traces and determine potential connections for crime scenes. It is also used in identifying fire and explosive residues. GC-MS can validate the presence of fire accelerants or other initiators.
- GC-MS plays a role in identifying compounds present within human blood or urine samples, aiding drug testing procedures. Its high sensitivity contributes crucial scientific evidence in various criminal investigations.
- Additionally, it assists in post-mortem examinations to determine the cause of death
- Environmental Monitoring
- The reliability of GC-MS finds extensive application in environmental monitoring, enabling the detection of various contaminants, including volatile organic compounds (VOCs), pesticides, and more, in air, water and soil samples.
- Food Industry
- In the food sector, GC-MS can be used for monitoring the contaminants present in food. Furthermore, it facilitates the analysis of food and beverage compositions to identify the flavours and aroma compounds that are contributing to their flavour. It helps assess ingredient quality, detect adulteration, and analyze fatty acid composition, contributing to overall food safety and quality.
TQ vs SQ
Curious about the different between single quad and triple quad mass spectrometers, dive into our article ‘Triple Quad vs Single Quad Mass Spectrometry – What’s the Difference?’
SCION has been performing GC-MS analysis for years. View some of our application notes utilising GC-MS analysis for a variety of different purposes:
- Flavour and Aroma Profile of Hops
- Headspace Assay of Polymers used in the Automotive Industry
- Determination of Hexanal in Foods
- Determination of Furan in Coffee
- Achieving Low-Level Detection of Benzene in Beverages
- Analysis of Dioxins
- Multiplexed Pesticide Analysis
GC-MS Systems from SCION Instruments
The SCION GC-MS range is designed for today’s fast paced analytical laboratory. Our lineup includes the 8700 Single Quad (SQ) MS and the 8900 Triple Quad (TQ) MS, both of which seamlessly integrate with our exceptional GC instruments, catering to the most demanding analytical requirements in terms of performance and productivity.