Charged fragments are focused and accelerated into a mass analyzer: typically a quadrupole mass analyzer.
When GC is coupled to a mass spectrometer, the compounds that elute from the GC column are ionized by using electrons (EI, electron ionization) or a chemical reagent (CI, chemical ionization). Qualitative identification of unknown compounds as well as quantitative analysis of samples is possible using GC-MS. Mass spectroscopy is one of the types of detection that provides the most information with only micrograms of sample. The mass spectrometer has become a standard detector that allows for lower detection limits and does not require the separation of all components present in the sample. Detectors that exhibit an enhanced response to certain analyte types are known as "selective detectors".ĭuring the last 10 years there had been an increasing use of GC in combination with mass spectrometry (MS). In total, approximately 60 detectors have been used in GC.
Most of the detectors used in GC were invented specifically for this technique, except for the thermal conductivity detector (TCD) and the mass spectrometer.
The detector senses a physicochemical property of the analyte and provides a response which is amplified and converted into an electronic signal to produce a chromatogram. A shorter run time and higher resolution can be achieved using thin films, however these films offer lower capacity. Moreover, the retention of sample components will be affected by the thickness of the film, and therefore its retention time. The sample capacity of the column will also depend on film thickness.By decreasing the column internal diameter, better separations can be achieved, but column overload and peak broadening may become an issue. The column internal diameter (ID) can influence column efficiency (and therefore resolution) and also column capacity.One of the classical trade-offs in gas chromatography (GC) separations lies between speed of analysis and peak resolution. A longer column will increase the peak efficiency and the quality of the separation, but it will also increase analysis time. The length is related to the overall efficiency of the column and to overall analysis time.Changing the stationary phase is the most powerful way to alter selectivity in GC analysis. The stationary phase is the parameter that will determine the final resolution obtained, and will influence other selection parameters.To define a capillary column, four parameters must be specified: Since most common applications employed nowadays use capillary columns, we will focus on this type of columns. A Basic Introduction, Copyright Dunnivant & Ginsbach (2008). Ginsbach, Gas Chromatography, Liquid Chromatography, Capillary Electrophoresis – Mass Spectrometry. Martin (Figure \(\PageIndex\) A Glass Packed GC Column.