Gas Spectrometry Lab Report

GC-MS (Gas Chromatography-Mass Spectrometry):

GC (Gas Chromatography): Gas chromatography is a method which is used for the separation and analysis of organic compounds (i.e. volatile compounds). For separation prime factor is volatility i.e. more volatile compounds elute first from the column and then detected by detector.

It is used for testing the purity and isolating of compounds. In it moving gas phase and stationary liquid phase is present which is used for partitioning process.

Mass Spectrometer (MS): Mass spectrometer is the generation, separation, and characterization of gas

The analyte extract and mixed with water then introduce into airtight chamber.

Gas (inert) is bubbled through water which is known as purging. Analyte move above the water and are drawn along pressure gradient out of the chamber.

Analyte trap in adsorbent, desorbed by heating and transferred to GC-MS where volatile compounds are analyzed Pyrolysis Method (polymer material): In this system, we thermally decompose the polymer material such as plastic, rubber and resin at 500 degree centigrade and then analyze the resulting pyrolysates by using GC/MS. Then fragments create through MS and by analysis of these fragments structure of the polymer can identify. Instrumentation:

1. Ionizers

2. Analyzers

3. Detectors

Types of ionization (EI & CI):

 EI(Electron Impact

2 opposite rods have + potential and other 2 have – potential. By applying AC and DC voltages only ions of specific m/z ratio pass through Q filter and reach to detector.

Only a particular mass ion can resonate properly and reach to the detector.

Due to the compact size and speed of the Quadrupole instruments these are to be efficient and powerful detectors.

Detectors:

1. FID(Flame ionization Detectors): These need H2 gas for flame burning. These used for oil and fatty acids profiling (fats composition can identify).

2. ECD (Electron Capture Detectors): These are costly than FID, and are used to detect pesticides and insecticides.

3. TCD(Thermal conductivity Detectors): These are the universal detectors and used for quantification.

Advantages of GC-MS: • High sensitivity and selectivity.

• High speed i.e. in 1 hour 80 pollutants can be analyzed in one analysis.

Disadvantages of GC-MS:

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• High cost.

• Maintenance (Time, expertise,