Details on an item of equipment
multidimensional gas chromatograph
The system is composed of:
- 2 gas chromatographs in line (GC-GC), Agilent 6890
- a crogenic transfert line, Gerstel (CTS1, CryoTrapSystem)
- a detector by mass spectrometry (MSD), Agilent 5973 with inert source of ionization
- a detector by ionization by flame (FID), Agilent
- an injector with programming of temperature (PTV), Gerstel
- a olfactory detection port (ODP), Gerstel
- a system of exchange of column Gerstel (DCS2, DualColumnSwitching System)
Thanks to the flexibility of the multidimensional system, the samples can be analyzed either by GC-FID, GC-MS, GC-MS-ODP, GC-GC-MS-ODP.
The introduction of the sample can take place in several forms:
- injection via injector PTV (liquids), 5 modes of injection are available according to the
concentration and of the type of sample
- injection by the transfer line coming from a purge and trap (Tekmar) (liquids, solids, foams)
- injection by SPME (Solid Phase Micro Extraction) (liquids, solids, gas)
This system allows a combination of two columns (GC-GC) of different types to carry out a better separation of the volatile compounds in the event of coelution.
The cryogenic transfer line and the system of exchange of column (DCS2) make it possible to cut a part of the chromatogram coming from the first GC and to concentrate it (nitrogen liquid). A fast reheating of the transfer line allows a new injection in the second GC (which has a column of the different type from the first GC, polar >< non-polar) where new programming of temperature makes it possible to separate the coeluated compounds.
Detection can be carried out by three different apparatuses (independently or in combinations):
- the detector by ionization by flame (FID) which is used as monitoring sensor (reference frame of time) for the multidimensional system (cutting) and like traditional detector in system GC-FID
- the detector by mass spectrometry (MS) whose principle is to split up the molecules in ions (by electronic impact, EI). The ions constitutive and specific to the compound are detected and entered (variation of the intensity with the concentration, quantitative and qualitative detection)
- the olfactory detection port (ODP) is composed of a mask out of inert glass coupled to a humidifier, of an inert capillary (not of stationary phase in the column) which established connection between the chromatographic system and the mask via a heated interface. In this case, the detector is the nose of the operator. By breathing throughout the analysis the compounds separated by gas chromatography, the operator is able to note the specific odors of each compound.