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Which type of chromatography is an analytical technique for separating compounds based primarily on their voltalities?
T/F: In the sample injection process for GC, the process is reproducible, highly efficient, and provides a representative sample for chromatographic separation.
What are 3 of the reasons you would derivatize your sample in GC?
- increase volatility and polarity
- decrease thermal stability
What is the difference between split and splitless injections?
T/F: As column length increases, resolution also increases.
As the _____ of the mixture increases, the elution speed decreases.
What are the 3 types of detectors in GC?
- Flame Ionization Detector (FID)
- Electron Capture Detector (ECP)
- Flame Photometric Detector (FPD)
Which detector is the most common in GC?
flame ionization dectector
Describe the FID.
- -most common
- -provides universal ionization by burning
- -immediate, stable, predictable response
- -sensitive with large dynamic range
- -destructive analysis
- -column effluent passes through the flame
Describe the ECD.
- Electron-Capture detector
- -as sensitive as FIDs but with limited dynamic range
- -uses radioactive beta-emitter to ionize carrier gas to produce current between electrodes
- Flame Photometric Detector
- -detection of sulfur and phosphorus specifically
- -chemiluminescent reactions occur in a hydrogen/air flame
- adjusted retention time
- tR' = tR - tM
the time a compound spends in the stationary phase
- time for unretained peak
- -the time a compound spends in the mobile phase
the total time that a compound spends in both the mobile and the stationary phase
- β= r/2df relates the column diameter and film thickness of the stationary phase
- distribution constant
- = concentration of solute in stationary phase
- concentration of solute in mobile phase
T/F: A large distribution constant means there was good separation with an increase in solute retention.
What are the 3 parameters affecting KD?
- stationary phase
capacity factor (or partition factor)
- the ration of the mass of a compound in the stationary phase relative to the mass of the compound in the mobile phase
- - a measure of the columns retention of a compound
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