CH11_13-Chromatography Flashcards

1
Q

Chromatography

A

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

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2
Q

Stationary phase

A

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

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3
Q

Mobile phase

A

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

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4
Q

Elution

A

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

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5
Q

Differential migration

A

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

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6
Q

Migration rate depends on

A

the strength of interaction between SAMPLE components with the stationary phase

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7
Q

Chromatography is useful as a tool to determine

A

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

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8
Q

Chromatography is more commonly used to

A

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

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9
Q

Adsorption chromatography

A

-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

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10
Q

Partition chromatography

A

-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

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11
Q

Ion-exchange chromatography

A

-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

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12
Q

Molecular exclusion chromatography

A

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

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13
Q

Affinity chromatography

A

-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

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14
Q

Normal Phase chromatography

A

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

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15
Q

Reversed Phase chromatography

A

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

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16
Q

Advantages of Reversed Phase chromatography

A

-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

17
Q

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

A

-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

18
Q

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

19
Q

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

20
Q

Diagram of typical Gas Chromatograph

A

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

21
Q

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

A

Oven = Sample injection chamber;Thermostat = Column and Detector

22
Q

Sample Introduction in GC

A

-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

23
Q

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

A

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

24
Q

HPLC

A

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

25
High efficiency (in HPLC)
analytes with only slightly different properties can be separated
26
Modern HPLC are almost exclusively?
liquid-liquid (partition) chromatography
27
Diagram of HPLC
Reservoir -> Pump -> Injector -> Column -> Detector -> Data system
28
HPLC Column/Column packing
-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)