Lecture 3: Efficiency and quantification P1 (finished) Flashcards
narrow peaks help you what?
separate compounds
Retention time is found where on the peak?
at the top
what another word for retention time?
hold- up time.
To diffuse the width of the peak you can measure form where?
base line or half way up the peak
Do nretained solute molecules travel down the column at the same rate as the carrier gas?
yes
quality of the separation is expressed mathematically by measuring what?
width
relative positions
peaks in the chromatogram
what are the fundamental parameters?
- retention factor (k),
- selectivity factor () ,
- column efficiency (N).
- resolution (R).
what is retention factor the measure of?
measure of how an analyte is
partitioned between stationary and mobile phase
whats the retention time equation?
k’= time analyse spends in sp/ time analyse spend sin mp
k ideally should be no more than what?
10
what is retention factor?
The retention factor is the ratio between the time a solute spends in the stationary and mobile phases.
Parameter influencing retention factor is?
Stationary phase
retention factor k slide
do it
in selectivity factor alpha is?
always more than 1
what is alpha defined as?
ratio of the two retention factors with the
larger one always being the numerator.
whats the Selectivity factor ( alpha) equation?
alpha=k’2/k’1 = t’2/t’1
what’s the t’2 and t’1 relationship int he Selectivity factor equation?
Where t’2 > t’1, so alpha > 1
what does k’ indicate?
k’ indicates where the peaks elute relative to Tm
what does the selectivity factor alpha show?
shows where the peaks elute relative to each other.
alpha represents what?
selectivity
whats k’1?
Retention factor of first peak
whats k’2?
Retention factor of second peak
what is selectivity a measure of?
Selectivity is a measure of the time or distance between two peaks.
what happens to the peaks if alpha = 1?
the two peaks have the same retention time and co-elute.
what is selectivity defined as?
Selectivity is defined as the ratio in retention factors.
what parameters influence retention factor?
- Stationary phase
- Mobile phase
- Temperature
what does Band broadening do?
reduces the efficiency of the separation being carried out
what type of band should be appleid to the column?
Important to ensure that a narrow band of mixture is applied to the column
injection volumes should be kept to a ?
minimum
is diffusion faster in liquids or gases?
10^4 times slower in liquids