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Analytical Chemistry > Chromatography 1 > Flashcards

Chromatography 1 Flashcards

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1
Q

Isocratic elution

A

The composition of the mobile phase is kept constant

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2
Q

Gradient elution

A

Composition of the mobile phase is varied

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3
Q

Stop-flow injection

A

The solutions are forced from syringes into a mixing chamber where they are mixed rapidly

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4
Q

Reverse-phase packing

A

Stationary phase of the chromatography is hydrophobic

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5
Q

Normal-phase packing

A

The stationary phase is polar and he mobile phase is nonpolar

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6
Q

Ion-pairing chromatography

A

A type of column chromatography where ions in solution can be paired or neutralized and separated as an ion pair in a reverse-phase column

Usually ionic compounds that contain hydrocarbon chains

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7
Q

Ion chromatography

A

Chromatography process that separates ions and polar molecules based on their affinity to the ion exchanger/stationary phase

Reverse phase packing

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8
Q

Bulk property detector

A

Compares an overall change in physical properties of the mobile phase with and without analyte

Measures some bulk physical property of the fluent

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9
Q

Solute property detector

A

Responds to the physical properties of the solute not shown in the mobile phase

Measure physical or chemical property unique to the solute

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10
Q

Sparging

A

Technique which involves bubbling a chemically inert gas, such as nitrogen, argon, or helium through a liquid

Can be used to remove dissolved gases from a liquid

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11
Q 
Retention factor (K)
(Capacity)
A

Time required to elite our peak (Tr) - the time for the mobile phase (Tm)

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12
Q

Selectivity factor (alpha symbol)

A

Based on stationary phase and its selectivity for the mobile phase and things in the mobile phase

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13
Q

Efficiency (N^(1/2)/4)

A

N = # if theoretical plates

The more theoretical plates the more efficient the column

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14
Q

Master Resolution Equation

A

Capacity x Selectivity x Efficiency

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15
Q

How to change Capacity

Gas chromatography

A

Change the temperature
(Lowering temp by 25 degrees C doubles k)

1

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16
Q

How to change Selectivity

Gas chromatography

A

Change the stationary phase

Alpha > 1.05

Alpha = Kb/Ka

17
Q

How to change Efficiency

Gas chromatography

A 
Increase column length (Lc)
Decrease column Diameter (Dc)
Decrease film thickness (Dt)
Optimize flow rate (FR)
Check column installation
18
Q

How to change Capacity

Liquid Chromatography

A

Weaken mobile phase

Increase %H2O by 10% ~2-3 x K

19
Q

How to change Selectivity

Liquid chromatography

A 
Change mobile phase 
Change stationary phase
Change pH
Change Temp
Change buffer
Change additive
20
Q

He to change Efficiency

Liquid chromatography

A

Increase column length (Lc)
Decrease particle diameter (Dp)
Optimize flow rate (u)
Minimize extra column volume

Analytical Chemistry (2 decks)

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