WHAT IT IS
Gas Chromatography–Mass Spectrometry (GC-MS) is a hybrid analytical technique that combines the separation power of gas chromatography (GC) with the molecular identification capabilities of mass spectrometry (MS). It is widely used for qualitative and quantitative analysis of volatile and semi-volatile compounds in complex mixtures.
HOW IT WORKS
In GC-MS, a sample is introduced into the GC system where it is vaporized and transported by an inert carrier gas through a separation column coated with a stationary phase. Compounds in the sample separate based on their volatility and interaction with the stationary phase, eluting from the column at different retention times.
As each separated compound exits the GC column, it enters the mass spectrometer. There, the molecules are ionized causing them to fragment into charged ions. These ions are then sorted by their mass-to-charge (m/z) ratios in a mass analyzer.
A detector records the ion intensities, producing a mass spectrum for each compound. This spectrum provides information on the molecular weight and structure of the analyte, allowing precise identification by comparison with spectral libraries
ADVANTAGES
Compound Separation and Identification: GC separates individual compounds, while MS identifies them based on their unique fragmentation patterns.
High Sensitivity and Selectivity: GC-MS can detect compounds at trace levels with high specificity, even in complex matrices.
Structural Information: Mass spectra provide molecular weight and structural clues, enabling identification without standards in many cases.
Quantitative Accuracy: With proper calibration, GC-MS delivers precise and reproducible quantitative results.
Broad Application Range: Effective for analyzing pesticides, drugs, pollutants, aroma compounds, hydrocarbons, and more.
Automated and High-Throughput Capability: Modern GC-MS systems support automated sample injection and data analysis, improving productivity.
CHALLENGES AND LIMITATIONS
Volatility Requirement: Only analytes that can be vaporized without decomposition are suitable; others may require chemical derivatization.
Matrix Interference: Complex sample matrices can cause ion suppression or background noise, affecting detection and accuracy.
Instrument Complexity: GC-MS systems are more complex and costly than standalone GC or MS systems, requiring skilled operation and maintenance.
Ion Source Limitations: Electron impact ionization, while widely used, may cause extensive fragmentation, making identification difficult for labile or large molecules.
Vacuum Dependence: The mass spectrometer requires a high-vacuum environment, making it sensitive to leaks and contamination.