Chromatographs, using either gas or mobile phases, can be coupled to mass spectrometers. This takes advantage of the capacity of chromatography to isolate organic compounds with the structural information provided by mass spectrometry.
In Gas Chromatography coupled to Mass Spectrometry (HRGC-MS), compounds leaving the GC column are ionized, comonly using a electron impact, and fragmented. The charged fragments are detected and a m/z (mass-to-charge) spectrum is produced. The fragmentation patterns of each molecule are reproducible and can be used to identify the molecule.
GC-MS can also be used to produce quantitative measurements by selectively monitoring of charged fragments of a specific mass. This a powerful technique to selectively quantify compounds of interests at very low concentrations in complex samples that contain many interfering compounds.
Systems based on High Performance Liquid Chromatography coupled to Mass Spectrometry (HPLC-MS) combine the capacity of separation of HPLC with the structural information provided by MS systems. The coupling of HPLC to MS systems requires interphases such as Eletrospray Ionization (ESI) and Atmospheric Pressure Chemical Ionization (APCI) that transfer the compound eluting from the HPLC column to the MS system.
Over the years, a wealth of MS systems have become commercially available to undertake different analytical goals. High resolution MS systems (Orbitrap, TOF, TOF/TOF, etc) are best to identify compounds or to provide structural information. However, triple quadupole low-resolution MS/MS systems (QQQ) are the optimal solution to detect and quantify organic compounds at trace levels.