gas chromatograph (GC)

Gas chromatography is a technique for separating chemical substances that

relies on differences in partitioning behavior between a flowing mobile phase and

a stationary phase to separate the components in a mixture. The flame ionization

detector (FID) is the most sensitive gas chromatographic detector for

hydrocarbons such as butane or hexane.

Principle of gas chromatography: The sample solution injected into the

instrument enters a gas stream which transports the sample into a separation

tube known as the "column." (Helium or nitrogen is used as the so-called carrier

gas.) The various components are separated inside the column. The detector

measures the quantity of the components that exit the column. To measure a

sample with an unknown concentration, a standard sample with known

concentration is injected into the instrument. The standard sample peak retention

time (appearance time) and area are compared to the test sample to calculate the

concentration.

Type of GC at Chem. Eng. Department

Agilent 6890 Gas Chromatograph with Flame Ionization Detector (GC-FID)

Type of GC at Chem. Eng. Department

2. Shimazu 14 A Gas Chromatograph with Thermal Conductivity Detector (GC-

TCD)

Phase Applications Polarity Temperaturerange °C

HP-FFAP(Nitroterephthalic acid modified

polyethylene glycol)(0.52 um, 0.32mm I.D.X25 m long)

Acids, Alcohols, Aldehydes, Acrylates, Ketones, Nitriles High polarity 60 – 240/250 °C

Inno-Wax (polyethylene glycol (PEG)

(0.5 um, 0.32mm I.D.X30 m long)

Alcohols, Free Acids, Aromatics, Essential Oils, Solvents High polarity -20 – 260 °C

HP-1(Cross linked Methyl Siloxane)

(0.88 um, 0.53mm I.D.X5 m long)

hydrocarbons, pesticides, polychlorinated biphenyls (PCBs), and

sulfur compounds. non polar -60 – 325/350 °

HP-5(5%-Phenyl)-methylpolysiloxane)(0.1 um, 0.1mm I.D.X10 m long)

Alkaloids, drugs, FAMEs, halogenated compounds, aromatic compounds non polar -60 – 325/350 °

DB-Wax(Polyethylene glycol (PEG)

(0.25 um, 0.32mm I.D.X30 m long)Alcohols,glycols, aromatics polar 40-240 °C

List of Capillary Column

GC Column Phase Selection Guide

Features of HP-1 Column

HP-5

Phase Applications

Molecular Sieve 5A(80/100 mesh, 3mm I.D.X2 m long)

a) The strong ionic forces of the divalent calcium ion makes it an excellent adsorbent to remove water, CO2, H2S from sour natural gas streams, while mini missing COS formation. Light mercaptans are also adsorbed.b) Separation of normal- and iso paraffin’s.c) Production of high purity N2, O2, H2 and inert gases from mixed gas streamsd) Static, (non-regenerative) dehydration of insulating glass units, whether air filled or gas-filled.

Porapak Q(50/80 mesh, 3 mm I.D. X 3 m long) atmospheric gases to organics.

Porapak R(50/80 mesh, 3 mm I.D. X 3 m long) analysis of gases, acids, amines, organics of low

carbon number and water

Inorganic gases

Inorganic gases

Resources and references

• https://www.slideshare.net/shaisejacob/gas-chromatography-ppt

• https://www.agilent.com/en/products/gas-chromatography/gc-columns/capillary#0 .

• Robert L.Grob. “Modern Practice of Gas Chromatiograhy” 2nd

Edition . John Wilet& Sons, N.Y. Singapore, 1985.• D.A.Skoog. “Principles of Instrumental Analysis” 3rd Edition,

Saunders College Publishing, 1985.