Gas Chromatography Research Paper

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Gas Chromatography
A gas chromatograph is an integral part of any organic analytical laboratory. Nowadays gas chromatography (GC) is considered to be the major technique for separation and analysis of fugitive compounds. It is used for analyzing liquids, gases, and solids, the latter usually being dissolved in fugitive solvents. GC can analyze both organic and inorganic materials, molecular weights of which can range from 2 to about1000 Daltons (Poole 43).
Chromatographic processes acquire their names due to the physical state of the mobile phase. Consequently, the mobile phase in gas chromatography (GC) is a gas, and the mobile phase in liquid chromatography (LC) is a liquid. The further subdivision
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Fig. 2. Scheme of the MS system

Flame ionization detectors Flame ionization detector (FID) is also one of the most frequently used types of detectors. In this system, the sample after leaving the column gets to the air-hydrogen flame. This flame has high temperature that leads to the process of pyrolysis, also called chemical decomposition, in the sample. This procedure releases the electrons and ions carrying current. The current is measured by a picoammeter with high impedance for monitoring the elution of the sample (Poole 136).
The advantage of FID using is the fact that the flow coefficient, water and noncombustible gases do not affect the detector. This feature of FID explains its low noise and high sensitivity. It is also quite effective and relatively easy in operation. The disadvantage of this technique is the necessity of using flammable gas that leads to the destruction of the sample (McNair & Miller 95).
The scheme of FID is shown in Figure 3. Fig. 3. Scheme of a simple flame ionization detector

Thermal conductivity
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7. Scheme of a CS Detector

Photoionization detector
Photoionization detector (PID) is another kind of GC detector which employs the features of CS. PID is a hand-held gas and vapor detector making selective identification of the aromatic hydrocarbons, some inorganic species, organo-heteroatom, and different organic components. An ultraviolet lamp is used in PID for emission of photons which are absorbed in the ionization chamber by the compounds leaving the GC column. Photoionization detectors can also be used in portable pick-and-go models, as well as in numerous lamp configurations (Poole 162).
The advantage of PID is that it gives almost immediate results. This type of detectors is frequently used for detection of volatile compounds in sediment, air, soil, and water, frequently used for detection of contaminants in atmospheric air and in soil. The major disadvantage of PID is that it is unable to identify some hydrocarbons having small molecular weight - ethane and methane, for example (McNair & Miller 131).
The scheme of PID is shown in Figure 8. Fig. 8. Scheme of PID detector
Application of GC method in real life
Nowadays, it is widely used in various fields – pharmaceutical industry, cosmetics industry and even during the detection of environmental

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