C3110 Final Flashcards
Mobile Phase
The phase in which the solute moves through the column
Eluent
Fluid entering column
Eluate
Fluid leaving the column
Stationary phase
Determines the amount of time the solute spends in the column
2 Main types of columns
- Packed
- Open Tubular
What are the 5 mechanisms of separation?
- Adsorption
- Partition
- Ion-exchange
- Size exclusion
- Affinity
Definition of retention time
Time between injection onto the column and when the component reaches the detector
Definition of retention volume
Volume of mobile phase reuired to elute a particular solute from the column
Dead time
Time required for an unretained solute to travel through the column
Volume flow rate
How many mL of solvent per minute travel through the column
Linear Flow rate
how many cm are travelled in 1 min by the solvent
What do we keep constant in terms of flow rate when changing column size?
Linear flow rate
Adjusted retention time
Time required for a solute to elute beyond the time for the solvent
Relative retention equation
a= tr2’ / tr1’
What value of alpha gives better separation?
Higher
Retention factor equation
k= (tr-tm) / tm
2 factors that contribute to how well compounds are separated
- Difference in elution time between peaks (farther apart = better separation)
- Peak broadness (wider peaks = poorer separation)
Column Resolution
how far apart two bands are relative to their widths (ability of the column to separate 2 solutes)
Plate Height
proportionality constant between variance of a band and distance travelled; length of column required for one equlibration
What is the plate height/number relation?
N=L/H
Does smaller or larger plate height give better resolution?
Smaller
Is a band narrow or wider for lower number of theoretical plates?
Wider
In the Purnell resolution equation, how are resolution and plate number related?
Resolution is proprtional to the square root of N
If the column length is increased by a factor of 4, how much does the resolution increase?
Factor of 2