CHAPTER 5 GC

What is the primary principle behind gas chromatography (GC)?

• Sample is heated to high temperatures

• Components are separated due to their partitioning between a mobile gaseous phase and a stationary phase

• Sample components are dissolved in a solvent

• Sample is directly injected into the detector

Which of the following is NOT a typical carrier gas used in Gas Chromatography?

• Helium

• Nitrogen

• Oxygen

• Hydrogen

What is the primary role of the carrier gas in GC?

• To cool the sample

• To transport analytes through the column

• To react with the analytes

• To stabilize the temperature of the detector

What is the ideal purity level of the carrier gas in GC?

• 90%

• 99.9%

• 99%

• 100%

Which of the following is an example of a liquid stationary phase in Gas-Liquid Chromatography (GLC)?

• Polydimethylsiloxane

• Graphite

• Aluminum oxide

• Silica gel

What is the function of the flow regulator in a GC system?

• To regulate the temperature of the detector

• To control the flow rate of the carrier gas

• To detect analytes in the sample

• To maintain the pressure in the column

In GC, what should be the condition of the samples being injected?

• Non-volatile

• Volatile and thermally stable

• Solid

• Gaseous only

What is the main purpose of the sample injection system in GC?

• To vaporize and mix the sample with the carrier gas before entering the column

• To detect the analytes in the sample

• To regulate the flow of the carrier gas

• To cool the sample

Which of the following is a disadvantage of the Flame Ionization Detector (FID)?

• High sensitivity to all analytes

• Insensitive to halogen-containing compounds

• Non-destructive

• Sensitive to non-combustible analytes like water and CO₂

In GC, what is the function of the detector?

• To inject the sample into the column

• To separate the components of the sample

• To detect and measure the components as they elute from the column

• To heat the sample before analysis