Chapter 7 Flashcards
To memorise and score the test
What are the main components of a gas chromatograph?
- Carrier gas flow
- Injector port
- Column
- Temperature-regulated oven
- Detector
What are the types of gas chromatography and their respective phases?
The types of gas chromatography are Gas Liquid Chromatography (GLC) with an immobilized liquid stationary phase, and Gas Solid Chromatography (GSC) with solid stationary phases such as alumina, silica, polymers, or carbon.
Why do industries commonly use gas chromatography?
- Simplicity
- Low cost
- Short analysis times
- High accuracy
- Applicability in qualitative and quantitative analysis at levels ranging from percent to parts per billion (ppb).
What are the mobile phases used in gas chromatography?
The typical carrier gases used as mobile phases in gas chromatography are nitrogen (N2), helium (He), and hydrogen (H2). Each gas has its advantages and compatibility with different detectors, resolution capabilities, and solute diffusion rates.
What is the purpose of the injection port in gas chromatography?
To load the sample to be analyzed into the system via a hypodermic syringe
How does the split injection system reduce the volume of the injected sample in gas chromatography?
In the split injection system, a controlled fraction of the injected sample is carried away by a gas stream before entering the column. This reduces the volume of the injected sample on the column.
What are some commonly used types of GC columns?
Commonly used types of GC columns include capillary columns and packed columns
What factors should be considered when selecting a GC column?
When selecting a GC column, critical parameters to consider include dimensions (internal diameter, column length, film thickness), conditions (temperature, flow rate), and composition (stationary phase composition, carrier gas). The choice of stationary phase is particularly important as it determines the types of samples that can be run
How does column temperature affect the separation in gas chromatography?
An increase in temperature gradient during separation increases the solute vapor pressure and decreases the retention time of the components being separated
How does a flame ionisation detector work in gas chromatography?
In a flame ionisation detector, sample components from the effluent are ionized by subjecting them to a flame. These ions are attracted towards an electrode based on their charge, and when they impinge on the electrodes, a current is passed and recorded
What are some methods used for qualitative and quantitative analysis in GC?
Mass Spectrometers and Fourier Transform Infrared Spectrometers can identify compounds as part of a GC system. Another method is comparing retention times (RT) between a reference sample and an unknown sample, using multiple columns with different stationary phases.
How is the number of components and the amount of a given component determined in GC analysis?
The number of components in a sample is determined by the number of peaks observed in the chromatogram. The amount of a given component is determined by the area under the peak. The identity of components can be determined by their retention times, but this must be coupled with another instrument, such as a mass spectrometer (MS)
