Chromatography Part A Obj 2 Flashcards
What is the function of the carrier gas for a GC?
Transport the sample through to column into the detector
How is the sample is inserted into the column?
Sample injector
What must be done to liquid samples before analysis in a GC?
Liquid sampled have to vaporize before injection into the carrier stream
What determines the speed at which sample components travel through the column?
Sample components travel at different speeds depending how strongly they are attracted to the stationary phase
What does the detector do?
Outputs a voltage based on the mass flow of material through it
What is the name for the plot of detector output signal over time?
Chromatogram
What are the 4 types of chromatography?
1) Gas Liquid
2) Gas Solid
3) Liquid Liquid
4) Liquid Solid
How are sample components identified in chromatography?
Peak retention times compared to a known standard sample
When you first set up a chromatograph what must be done to facilitate sample identification?
A standard sample is injected which gives the retention times of known components.
What is the most common type of process chromatography?
Gas Liquid Chromatography since it is used to separate mixtures of hydrocarbons and organic compounds
What 2 conditions must be met to ensure proper performance of GLC?
1) Columns must be heated to maintain the sample in it’s gas phase
2) Temperatures must be kept below the liquid phase boiling point
What is a homologous series?
A family of hydrocarbons know to have similar chemical and physical properties for example straight-chain alkanes
Describe the process of partitioning as it pertains to chromatography
Based on how volatile a component is, highly volatile components dissolve in stationary phase but low volatility components stay in the mobile phase
What 2 factors affect the partitioning behavior of a sample?
1) Substance boiling point
2) Solubility in the liquid phase
What is polarity?
Amount of unbalanced charge on a molecule
What does a process chromatograph determine?
1) Determine the identity of a component based on it’s retention time (qualitative analysis)
2) Determine the component concentration based on the peak area (quantitative analysis)
What two factors determine peak area?
1) Concentration of the component
2) Detector sensitivity to a certain component
How are differences in detector response to different compounds accounted for in
quantitative chromatography?
Calibrating the instrument to determine the response factor
