Electron impact can be coupled to GC systems as a combination of two different techniques: gas chromatography for the separation of the compounds and mass detection to identify and quantify compounds as they elute from the column.
The compounds are bombarded with a stream of electrons causing them to break apart into fragments. These fragments can be large or small pieces of the original molecules. GC-MS spectrometer signal is highly specific: the fragmentation pattern is unique for a given compound. This fingerprint can be used to identify the compound.
Mass spectrometers are useful in identification and structure elucidation of organic compounds: molecular weight, molecular formula, fragmentation pattern and chemical structures.
The detector is capable of creating an electronic signal whenever the presence of a compound is detected. The greater the concentration in the sample, the bigger the signal.
By combining the two techniques, we can both qualitatively and quantitatively evaluate a solution containing a number of chemicals.