ABSTRACT
This chapter discusses the basic concepts of Gas chromatography–mass spectrometry (GC-MS). It examines advancements in sample introduction, chromatographic separation, mass analyzers, and the different applications of GC-MS in environmental analysis. The use of multidimensional gas chromatography coupled to MS is on the increase. Low–pressure GC uses a short microbore column at the injector side, connected to a zero dead volume connector to a short megabore column to be used with higher gas velocities. The principle of negative chemical ionization is the same as that of electron capture detection, whereby a low-energy electron is captured by an electronegative sample molecule, forming a molecular anion that may undergo fragmentation, depending on its structure, thus generating a mass spectrum. In electron impact ionization, the gaseous analyte is bombarded by a beam of electrons at 70 eV. Consequent ionization of molecules takes place by the loss of one electron.
