Newton 5 Flashcards
What are two basic types of chromatography?
Column - stationary phase is a tube.
Planar- stationary phase on a plane.
What is chromatography?
Is the separation of two or more substaces by virtue of their different affinities toward a stationary phase and a mobile phase that moves in relation to the stationary phase.
What information the peak of column chromatography provides?
The area under the peak provides a quantitative measure of each component. The bigger the peak the more component is present.
Why in column chromotography band broadening occurs?
Because there is a difference in paths that molecules travel. Some molecules travel longer paths to the sensor tham other, so they will arrive later than molecules taking shorter path.
Perfect chromatography should yield peaks that are symmetrical about the retention time (tR) of the particular component - Gaussian (normal distribution) μ=tr. How can we achieve that with K?
Coefficient K must be linear, i.e ideal in behavior.
What couses fronting?
Column not working properly. Either not really performing chromatography so that the mobile phase or stationary phase is not appropiate for material. Or that you have overloaded it, too much material.
What causes tailing?
Fret (filter) can be partially blocked, there is a void in the begining of the column, stationary phase can have crack or void in it, or solvent do not work properly.
What are two ways resolution can be increased?
Increasing separation and decreasing bandwidth.
How to calculate resolution?
Where W is with of the peak, annd t is retention time.
What is plate height (H)?
Way of describing how sharper peak is. Also known as height equivalent to theorethical plate (HETP)
What is plate count (N)?
Known as number of theorethical plates
How you calculate plate count (N) using length of the column?
N= L / H
where H is plate height, L is length of the column packing
How is H deffined?
His the length of column that will contain the fraction of the analyte between L and (L-1σ)=34% of analyte,
H= σ2 / L , where σ is variance, L- length of the column
How can we calculate N with ideal Gaussian shape?
where t is retention time,
