Analytical Exam 2 - Ch. 22

Front 1

adsorption chromatography

Back 1

- solid stationary phase
- liquid or gaseous mobile phase
- solute adsorbed on surface of solid particles
- more strongly a solute is adsorbed, the slower it travels through the column

Front 2

partition chromatography

Back 2

- liquid stationary phase bonded to a solid surface, typically inside of silica chrom. column
- solute equilibrates btw stationary liquid and mobile phase, which is gas in GC

Front 3

ion-exchange chromatography

Back 3

-anions are covalently attached to the stationary solid phase (resin)
- solute ions of opposite charge are attracted to stationary phase
- mobile phase is a liquid

Front 4

molecular exclusion chromatography (aka size exclusion, gel filtration, gel permeation)

Back 4

- separates molecules by size - larger passes through quickest
- interaction between the staionary phase and the solute
- liquid/gaseous mobile phase passes through porous gel - large molecules don't fit and pass through, small molecules take longer to travel because they have to pass through the gel before leaving the column

Front 5

affinity chromatography

Back 5

- employs specific interactions between one kind of solute molecule and a second molecule that is covalently attached to the stationary phase

Front 6

plate height (H)

Back 6

- the smaller the plate height, the narrower the bandwidth
- N = L/H - rather have smaller "L" and larger "N", smaller "H"

Front 7

van Deemter equation: H ~ A + B/ux + Cux

Back 7

-packed columns: all terms contribute to band braodening
- open columns: A = 0 --> bandwidth decreases and resolution increases
- capillary electrophoresis: A&C = 0 --> reducing plate height and providing extraordinary separation powers

Front 8

longitudinal diffusion

Back 8

the faster the linear flow, the less time spent in the clumn, the less diffusional broadening occurs

Front 9

mass transfer in stationary phase

Back 9

dcreasing stationary phase thickness, d, reduces plate height and increases efficiency because solute can diffuse faster from the farthest depths of the stationary phase into the mobile phase

Front 10

mass transfer in mobile phase

Back 10

decreasing column radius, r, reduces plate height by decreasing the distance through which solute must diffuse to reach the stationary phase

Front 11

open tubular columns

Back 11

- provide higher resolution
- increased sensitivity to small quantities of analyte
- higher flow rate than packed column
- for high performance, radius of column must be small and stationary phase must be as thin as possible

Front 12

overload

Back 12

as the concentration of solute increases, the solute becomes more and more soluble in the stationary phase
--> so much that stationary phase begins to resemble solute

Front 13

tailing

Back 13

when small quantities of solute are retained more strongly than large quantities - gradually decreasing concentration after the peak
- sites that bind solute strongly cause tailing
- silanization reduces tailing by blocking the hydroxyl groups with nonpolar trimethylsilyl groups

Front 14

Resolution

Back 14

> 1.5
- doubling column length increases resolution by 2^1/2

Front 15

Volume flow rate

Back 15

tells how many mL of solvent per minute travel through the column

Front 16

linear flow rate

Back 16

tells how many cm are travelled in 1 min by the solvent