CH11_13-Chromatography

Question 1

Chromatography

Answer 1

a technique that separates a mixture into individual components when the mixture is carried through a stationary phase by a mobile phase

Question 2

Stationary phase

Answer 2

-the phase that is fixed in place in chromatography column or plate;-could be solid or liquid

Question 3

Mobile phase

Answer 3

-the phase that carries the analyte mixture through the stationary phase;-could be gas or liquid

Question 4

Elution

Answer 4

the process in which analytes are carried through the stationary phase by the movement of the mobile phase

Question 5

Differential migration

Answer 5

SAMPLE components migrate at different rates through the stationary phase (column)

Question 6

Migration rate depends on

Answer 6

the strength of interaction between SAMPLE components with the stationary phase

Question 7

Chromatography is useful as a tool to determine

Answer 7

the absence or presence of components of mixtures whose identities are known

Question 8

Chromatography is more commonly used to

Answer 8

separate a mixture before individual components are analyzed by other techniques such as mass spectrometry

Question 9

Adsorption chromatography

Answer 9

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

Question 10

Partition chromatography

Answer 10

-a liquid stationary phase is bonded to a solid surface, which is typically the inside of the silica chromatography column in gas chromatography;-solute equilibrates between the stationary liquid and the mobile phase

Question 11

Ion-exchange chromatography

Answer 11

-anions or cations are covalently attached to the stationary phase, usually a resin;solute ions of the opposite charge are attracted to the stationary phase;-mobile phase is a liquid

Question 12

Molecular exclusion chromatography

Answer 12

-also called size exclusion, gel filtration, or gel permeation;-separates molecules by size, with the larger solutes passing through most quickly

Question 13

Affinity chromatography

Answer 13

-most selective;-employs specific interactions between one kind of solute molecule and a second molecule that is covalently attached to the stationary phase;-once undesired solutes have been washed from column, desired one is dislodged by changing the pH

Question 14

Normal Phase chromatography

Answer 14

-polar stationary phase, less polar mobile phase;-least polar solute eluted first

Question 15

Reversed Phase chromatography

Answer 15

-nonpolar stationary phase, more polar mobile phase;-least polar solute eluted last

Question 16

Advantages of Reversed Phase chromatography

Answer 16

-water (aqueous buffer) can be used as the mobile phase (inexpensive, nontoxic, and biocompatible);-faster elution (mass transfer is faster ;-75% of all HPLC separations are performed with RP

Question 17

Adsorption chromatography is ______ phase (normal or reverse); Why?

Answer 17

-fine, porous silica or alumina particles with large surface area; since the surface of silica (or alumina) particles are polar, adsorption chromatography is normal-phase

Question 18

In HPLC, the more similar in polarity the mobile phase is to the stationary phase, the ______ the mobile phase

Answer 18

stronger

Question 19

In HPLC, the stronger the mobile phase, the _____ the elution

Answer 19

faster

Question 20

Diagram of typical Gas Chromatograph

Answer 20

Carrier gas tank -> Flow regulators -> Sample injection chamber -> Column -> Detector -> Flow meter and Data system

Question 21

In a Gas Chromatograph, what makes up the Oven and Thermostat

Answer 21

Oven = Sample injection chamber;Thermostat = Column and Detector

Question 22

Sample Introduction in GC

Answer 22

-Liquid samples are injected through a septum with a micro-syringe;-The sample is vaporized in the sample port;-The vaporized sample is swept onto the GC column by the mobile phase

Question 23

How is the sample vaporized in the sample port in a GC

Answer 23

the sample port is heated around 50-C above the boiling point of the least volatile component in the sample

Question 24

HPLC

Answer 24

using “a column packed with very small particles” and the use of a “high pressure difference across the column to drive the mobile phase” to improve the efficiency of liquid chromatography

Question 25

High efficiency (in HPLC)

Answer 25

analytes with only slightly different properties can be separated

Question 26

Modern HPLC are almost exclusively?

Answer 26

liquid-liquid (partition) chromatography

Question 27

Diagram of HPLC

Answer 27

Reservoir -> Pump -> Injector -> Column -> Detector -> Data system

Question 28

HPLC Column/Column packing

Answer 28

-usually stainless steel;-stationary phase support: porous particles of silica, alumina, or synthetic resin;particle size: 3-5 microns, 5 mostly;-a thin layer of stationary phase is coated onto the stationary phase (bonded or absorbed)