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Instrumental Chemistry > Exam 3 > Flashcards

Exam 3 Flashcards

(75 cards)

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1
Q

Separation

A

Dividing a group into smaller groups that share the same type of similar trait

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2
Q

2 Common Separation Techniques

A

A. Chromatography

B. Electrophoresis

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3
Q

Chromatography

Define and give three examples

A

An interaction between two phases; the mobile phase and the stationary phase.
Ex. Gas Chromatography (GC), Liquid Chromatography, Supercritical Fluid Chromatography

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4
Q

Supercritical Fluid

A

Something that moves like a gas, but dissolves like a liquid

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5
Q

Elution

A

Describes the separation of analyses on a packed column

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6
Q

Dilution occurs in a column due to…..

A

The addition of solvents to push the analyte thru

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7
Q

Eluent

A

Portion of the sample in the mobile phase

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8
Q

Mobile Phase vs. Stationary Phase

A

The phases that interact in chromatography

  • mobile: phase that moves
  • stationary: phase that does not move
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9
Q

Partitions

A

Formed as analytes move down the column

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10
Q

Column Chromatography:

The rate that a zone migrates down a column is dependent on…..

A

How long the analyte spends in the stationary phase.

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11
Q

Chromatogram

A

Readout that shows the detector response over time

  • x-axis = time
  • y-axis can vary
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12
Q

Formula:

Distribution Constants

A

K = cs/cm

(cs=ns/vs)
(cm=nm/vm)

  • v=volume, s=stationary phase, m=mobile phase
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13
Q

Parts of the HPLC inlets (3)

A
  • injection system
  • pump
  • solvent
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14
Q

Calculating Resolution:

A

Rs = 2( (tr)B - (tr)A) ) / (WA + WB)

  • trA = retention time of A
  • trB = retention time of B
  • WA = width of peak A
  • WB = width of peak B
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15
Q

Calculating Plate Count:

A

N = L/H

N = plate count (# of plates)
L = column length
H = plate height
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16
Q

Calculating Plate Height:

A

H = sigma^2 / L

H = plate height
sigma = distance from peak, one distribution out
L = column length
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17
Q

Diffusion

A

process in which species migrate from a more concentration part of a medium to a more dilute region
*no direction

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18
Q

The _____ the analytes are on the column, the _____ the longitudinal diffusion.

A

longer; greater

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19
Q

Gas Chromatography:

  • mobile phase
  • stationary phase
A
  • mobile phase: inert gas

- stationary phase: varies (solid, gel)

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20
Q

Gas Chromatography:

Information about Inlets

A
  • sample injection is complex due to gas rapidly flowing into the column
  • injection of either liquid or gas sample
  • sample must be volatilized, temperature must be high enough
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21
Q

Gas Chromatography:

Important parts of the Inlet

A
  • septum: keeps gases separate from atmosphere
  • syringe: used to puncture septum and inject sample
  • vaporization chamber: vaporizes sample, pushes the injection mix into mobile phase
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22
Q

Gas Chromatography:

Information about the Column

A
  • piece of instrument that causes separation to occur

- 2 types of columns: Open Tubular & Packed

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23
Q

Gas Chromatography:

Open Tubular Columns

A

WCOT and SCOT

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24
Q

Gas Chromatography:

WCOT

A

“Wall Coated Open Tubular” column

- capillary tube is coated with stationary phase

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25
Gas Chromatography: | SCOT
"Support Coated Open Tubular" column | - stuff inside the tube is coated with stationary phase
26
Gas Chromatography: | What is more efficient WCOT or SCOT?
WCOT is more efficient than SCOT.
27
Gas Chromatography: Most widely used column Advantage and Disadvantage
FSWC (fused silica wall coated, open tubular column) - + thinner, flexible - - can not add a large amount of sample
28
Gas Chromatography: | Packed Columns
tube packed with fine material coated with thin layer of stationary phase
29
Generic setup of GC
inlet --> column --> detector
30
Examples of common stationary phases
- PEG - dimethylpolysiloxane - wax
31
2 Methods of Temperature Ramp
A. Isothermal - keep same temperature throughout analysis | B. Gradient - increase temperature at some rate
32
Gas Chromatography: | As temperature _______, analytes will spend _____ time in mobile phase, _______ing the total time on the column
Increases; more; decreasing
33
Advantage and Disadvantage of Isothermal Temperature Ramp
+ easier to develop method | - longer runtimes and worse separations
34
Advantage and Disadvantage of Gradient Temperature Ramp
+ give better resolution and shorter runtime | - tricky to correct
35
Gas Chromatography: | Ideal Detector Characteristics
- sensitivity - good stability/reproducibility - linear response to solutes over many magnitudes - short response time - high reliability + ease of use - non-destructive
36
Gas Chromatography: | Common Detectors
``` A. FID B. ECD C. Thermionic Detectors D. Conductivity Detectors E. Photoionization F. Atomic Emission G. Flame Photometric H. Mass Spec. ```
37
Gas Chromatography: | FID
Flame Ionization Detector - detector in GC - very common - burns whatever comes out of column - mass sensitive - does not discriminate between hydrocarbons
38
Gas Chromatography: | ECD
Electron Capture Detector - detector in GC - useful in detection of halogenated compounds
39
Gas Chromatography: | Thermionic Detectors
- detector in GC - specific for phosphorus and nitrogen - hot gas flows, forms plasma, current is generated and detected
40
Gas Chromatography: | Conductivity Detector
- detector in GC - gas dissolved in liquid to produce conductive solution - detected in conductivity cell
41
Gas Chromatography: | Photoionization
- detector in GC | - uses light to ionize
42
Gas Chromatography: | Atomic Emission
- detector in GC | - converts sample to plasma and observes emissions
43
Gas Chromatography: | Flame Photometric
- detector in GC | - used for pollution studies
44
Liquid Chromatography: | Common Types
- HPLC - UPLC - Column Chromatography - TLC - Paper Chromatography
45
HPLC
High Pressure Liquid Chromatography
46
UPLC
Ultra high Pressure Liquid Chromatography
47
TLC
Thin Layer Chromatography (Liquid)
48
Liquid Chromatography: Mobile Phase: Stationary Phase:
Mobile Phase: liquid | Stationary Phase: varies
49
Liquid Chromatography: | Information about Columns
- columns generally packed with small particles | - smaller the particles, the better the efficiency of the column
50
Isocratic
same solvent at all times during run
51
Gradient
mixture of 2 solvents with different polarities; mixture changes during run
52
Liquid Chromatography: | Parts of the Inlet
- injection system - pump - solvent
53
Liquid Chromatography: | Function of Injection System
- allows ability to inject sample; would not be able to inject sample into just the inlet due to high pressure area
54
Liquid Chromatography: | Function of Pumps
forces solvent thru the inlet; irregular flow can cause issues that alter data
55
Liquid Chromatography: | Function of Column
where separation occurs; polarity based separations
56
Liquid Chromatography: | Separations are based on
POLARITY
57
Polarity of long CH chains.....
long CH chains are NON-POLAR
58
The larger the chain......
the more non-polar the molecule
59
Liquid Chromatography: | Common Columns in HPLC
A. Normal Phase | B. Reversed Phase
60
Liquid Chromatography: | Normal Phase
Column in HPLC | *polar stationary phase
61
Liquid Chromatography: | Reversed Phase
Column in HPLC | *non-polar stationary phase
62
Liquid Chromatography: | Rules for Columns in HPLC
***like dissolves like*** molecules with corresponding polarity to stationary phase will remain on column. If column is polar, polar molecules will remain on column.
63
Column Types
A. Guard Column - short, filled with packing material; purpose is to catch anything that will damage analytical column B. Analytical Column - where separation occurs
64
What can affect column performance?
TEMPERATURE; temperature should be kept constant throughout analysis
65
Liquid Chromatography: | Selection of Detector is based on
SAMPLE CONCENTRATION
66
Liquid Chromatography: | Types of Detectors
A. Bulk Detectors - measures some property of mobile phase | B. Solute-Property Detectors - measures some property of solutes (analytes)
67
Liquid Chromatography: | Advantage and Disadvantage of IR and Diode Array Detectors
+ gives structural info about analyte | - 3D graphs can be resource problematic
68
Liquid Chromatography: | Advatgage and Disadvantage of Electrochemical Detectors
+ cheap to install, high sensitivity, quick and easy | - pH dependent which impacts redox potentials
69
Electrophoresis
Is NOT Chromatography
70
Is electrophoresis Chromatography?
NO
71
Electrophoresis is NOT Chromatography
U right
72
Types of electrophoresis
1. Capillary electrophoresis 2. Slab gel electrophoresis 3. Combinations
73
Slab gel electrophoresis
Uses thin flat layer/slab of porous gel containing aqueous buffer solution in its pores; analytes form bands as electricity is applied
74
What field is slab gel electrophoresis used in?
BIOLOGY; separation of DNA/proteins
75
Why does pH matter in electrophoresis?
Due to supply of ions; lower pH gives larger supply of H+ ions

Instrumental Chemistry (5 decks)

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