Gas Chromatography

Question 1

used to separate mixtures of compounds that are volatile or can be made volatile

Answer 1

Gas Chromatography

Question 2

GC may be gas–solid chromatography, with a ______ stationary phase, or gas–liquid chromatography (GLC), with a ____________ _______ stationary phase.

Answer 2

solid; nonvolatile liquid

Question 3

It is commonly used in clinical laboratories.

Answer 3

Gas Chromatography

Question 4

The setup is similar to HPLC, except that the mobile phase is a gas and samples are partitioned between a gaseous mobile phase and a liquid stationary phase. The carrier gas can be

Answer 4

nitrogen, helium, or argon

Question 5

Sample vapor is swept through the column partially as a gas and partially dissolved in the liquid phase. Volatile compounds that are present mainly in the gas phase will have a low partition coefficient and will move ______ through the column.
Compounds with higher boiling points will move ______ through the column.

Answer 5

quickly; slowly

Question 6

used both to identify the compounds by the retention time and to determine their concentration by the area under the peak

Answer 6

Chromatogram

Question 7

Components of Gas chromatography

Answer 7

1. Columns
2. Detectors

Question 8

• Are generally made of glass or stainless steel and are available in a variety of coil configurations
• These columns are usually 1/8 to 1/4 inch wide and 3 to 12 feet long. Capillary wall–coated open tubular columns have inside diameters in the range of 0.25 to 0.50 mm and are up to 60 m long.

Answer 8

Gas Chromatography Columns

Question 9

The ________ layer is coated on the walls of the column. A ______ support coated with a liquid stationary phase may in turn be coated on column walls. The liquid stationary phase must be ___________ at the temperatures used, must be thermally _______, and must not react chemically with the solutes to be separated. The stationary phase is termed _______________ when separation is primarily based on relative __________ of the compounds.

Answer 9

liquid; solid; nonvolatile; stable; nonselective; volatility

Question 10

used to separate polar compounds based on relative polarity

Answer 10

Selective liquid phases

Question 11

• Only thermal conductivity (TC) and flame ionization detector are the most stable
• The sample components usually have a lower TC, increasing the temperature and resistance of the sample filament.

Answer 11

Detectors

Question 12

which has a high TC, is usually the carrier gas. Carrier gas from the reference column flows steadily across one filament, cooling it slightly

Answer 12

Helium

Question 13

amplified and fed to the recorder. The electrical change is proportional to the concentration of the analyte.

Answer 13

Electrical change

Question 14

widely used in the clinical laboratory. They are more sensitive than TC detectors.

Answer 14

Flame ionization detectors