GCMS

Gas chromatography–mass spectrometry (GC-MS) is an analytical technique that combines gas chromatography for separating volatile compounds with mass spectrometry for identifying and quantifying them. It is widely used for substances that can be vaporized without decomposition, offering high sensitivity and specificity.

The GC component uses a capillary column and an inert carrier gas to separate components by volatility and interaction with the coating. The effluent enters the mass spectrometer, where molecules are ionized (commonly by electron impact or chemical ionization) and analyzed by a mass analyzer such as a quadrupole or time-of-flight. Fragmentation patterns yield spectra that serve as unique fingerprints; tandem MS adds selectivity.

Typical workflows include sample preparation, injection, GC separation, ionization, and mass analysis, followed by data interpretation. Quantification is achieved by calibration against standards, often with internal standards. Identification relies on spectral libraries and retention indices.

Applications include forensic toxicology, environmental monitoring, food safety, pharmaceuticals, fragrance analysis, and metabolomics. GC-MS can detect trace solvents, pesticides, drugs, and pollutants, and can distinguish compounds with similar retention times by their spectra.

Limitations include the requirement for volatility and thermal stability, possible derivatization for nonvolatile compounds, and relatively high instrument and maintenance costs. Matrix effects and ion suppression may occur. Method development requires expertise in chromatography, ionization, and spectral interpretation. Quality-control procedures rely on validated libraries, internal standards, and reproducibility checks.