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Analytical Chemistry > Chromatography > Flashcards

Chromatography Flashcards

Analytical Separation, General Principles of Chromatography, Gas Chromatography, Liquid Chromatography

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1
Q

Separation techniques based on the size (4)

A
  1. filtration
  2. dialysis
  3. size-exclusion chromatography
  4. electrophoresis
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2
Q

Separation techniques based on the mass or density (1)

A

centrifugation - spinning sample at high speed

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3
Q

Separation techniques based on complex formation (1)

A

masking/demasking

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4
Q

Separation techniques based on change in physical state/physical method (3)

A
  1. distillation
  2. sublimation
  3. crystallization
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5
Q

Separation techniques based on change in chemical state/chemical method (3)

A
  1. precipitation
  2. electrodeposition
  3. volatilization (involves chemical reaction)
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6
Q

Separation techniques based on partitioning between phases (2)

A
  1. extraction
  2. chromatography
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7
Q

Describe filtration

A

separates a particular interferent from solute analytes using a filter with a pore size that will retain the interferent (particle size must be consider)

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8
Q

Differentiate filtrate and retentate

A
  1. Filtrate - solution that passes through the filter
  2. Retentate - material that is retained by the filter
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9
Q

used for particulates that are too small to be retained by filter paper

A

membrane filter

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10
Q

Differentiate types of membrane filter

A
  1. centrifugal filter - macromolecules (10^6 g/mol)
  2. syringe filter - smaller particles (0.45 µm)
  3. disposable filter - cellulose acetate (0.22 µm)
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11
Q

Define masking

A

binding the interferent in a strong, soluble complex that prevents it from interfering in the analyte’s determination

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12
Q

Define distillation

A

process of separating two liquids that have different boiling points.

  • liquid is converted to its vapor
  • collecting the vapor as liquid by condensation
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13
Q

Differentiate types of distillation (4)

A
  1. Simple distillation
    - analyte does not go decomposition before its boiling point (large boiling point difference)
  2. Fractional distillation
    - similar boiling points; uses fractionating column
  3. Vacuum distillation
    - substances that boil above 200 ºC at 1 atm
    - distillation at reduced pressure
  4. Steam distillation
    - passing dry steam through the sample whereby the steam volatile compounds are volatilized
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14
Q

process of collecting the distillate in several fractions and subjecting the fractions to systematic redistillation

A

rectification

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15
Q

type of short-path vacuum distillation.
used to separate substances that decompose at the boiling temperature even in high vacuum

A

molecular distillation

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16
Q

Used if the material to be extracted is
immiscible, chemically non-reactive with water, and temperature sensitive

A

Steam Distillation

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17
Q

Describe sublimation and when it is used?

A

a solid directly converted into gas without converting into the liquid phase

  • mostly used for separation of non-volatile compounds from volatile compounds
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18
Q

compounds that are capable of sublimation tend to be those with _____ such as ___

A

weak intermolecular forces in the solid state

compounds with symmetrical or spherical structure

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19
Q

How to choose solvent to use in crystallization?

A

When solvent is hot - significant solubility of analyte/ less soluble interferant

When solvent is cold - minimal solubility of analyte/

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20
Q

Process of recrystallziation

A
  1. cycle of adding hot solvent and sample then cooling in ice bath
  2. rinsing and drying the crystals
  3. recrystallize for further purification
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21
Q

converting the analyte in another form before separating

A

Separation by chemical reactivity

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22
Q

require large solubility differences between the analyte and potential interferences

A

Separation by precipitation

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23
Q

____ are good reagent for separating metal since most metal ions except alkaline and alkali are _____

A

Sulfides; very insoluble with sulfides

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24
Q

_____ ions are often used as precipitants for cations, but they are not ____

A

phosphate, carbonate, and oxalate
selective

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25
Q

chloride can separate ____ from ____

A

silver; most other metals

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26
Q

sulfate can isolate a group of metals that includes _____

A

lead, barium, and strontium

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27
Q

Separate nickel ion using ____ precipitant

A

dimethylglyoxime

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28
Q

Separate aluminum ion using ____ precipitant

A

8-hydroxyquinoline

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29
Q

Describe separation by Electrolytic Precipitation

A

metals are deposited in an electrode by controlling the potential of the working electrode

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30
Q

How will you separate a miscible solution of benzene and CHCl3?

A

Distillation - separation of two liquids

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31
Q

Iodine can be purified by ____. Why?

A

Sublimation, iodine is volatile and can sublime

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32
Q

A mixture of camphor and KCl is best separated by ____

A

sublimation - camphor can be easily sublime

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33
Q

A mixture of camphor (BP = 209 degree C) and benzoic acid (BP = 249 degree C) can be separated by ____. Why?

A

Chemical method
- benzoic acid, an acid can react with the base, but camphor is an organic compound which does not react with either acid or base, hence, NaHCO3 will be used to react with benzoic acid which will become sodium benzoic which is water soluble that can be extracted

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34
Q

o-Xylene and m-Xylene products of the same compounds can be separated by ____

A

crystallization - different melting point

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35
Q

A mixture of iron and copper filings can
be separated by ____

A

physical method (magnet separation0

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36
Q

the transfer of a solute from one phase to
another to isolate or concentrate the desired analyte

A

extraction

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37
Q

Types of extraction (4)

A
  1. liquid-solid (SPE)
    - liquid sample
    - solid extractant (absorbent)
  2. solid-liquid
    - solid sample
    - liquid extractant
  3. liquid-gas
    - liquid sample
    - gas extractant
  4. liquid-liquid
    - liquid sample
    liquid extractant
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38
Q

Types of Adsorption Solid Phase Extraction (SPE)

A
  1. Normal - least polar compounds elute first
  2. Reverse - most polar compounds elute first
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39
Q

Types of Ion Exchange Solid Phase Extraction (SPE)

A
  1. Cation - Weakly ionized compounds elute first; cations retained
  2. Anion - Weakly ionized compounds elute first; anions retained
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40
Q

In solid-liquid extraction, continuous extraction of a solid sample is carried out using a ____

A

Soxhlet extractor

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41
Q

Solid-liquid extraction is used when ____

A

used when the desired compound has a limited solubility in a solvent and the impurity is insoluble in that solvent

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42
Q

Three main sections of solid-liquid extraction

A
  1. Percolator (boiler and reflux)
    - circulates solvent
  2. Thimble
    - retains the solid to be extracted (made of thick filter paper or membrane)
  3. Siphon mechanism
    - periodically empties the thimble
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43
Q

In liquid-gas extraction, _____ can be quantitatively removed from a liquid sample by a method called _______

A

volatile organic compounds (VOCs)
purge-and-trap

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44
Q

Explain liquid-liquid extraction and its phases

A

the solute partitions itself between two immiscible phases which usually done using separatory funnel

  1. Aqueous solvent
  2. Organic solvent
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45
Q

_____ (3) are common solvents that are immiscible with and less dense than water (floats on top)

A

Diethyl ether, toluene, and hexane

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46
Q

_____ (3) are common solvents that are denser than water (below aqueous phase)

A

Chloroform, dichloromethane, and carbon tetrachloride

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47
Q

Many _____ extractions are more effective than a few ____ extractions

A

Many small extractions are more effective than a few large extractions

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48
Q

If a solute is an acid or base, its charge changes as the pH is changed. Usually, a ____ is more soluble in an organic solvent and ____ is more soluble in aqueous solution.

A

neutral species is more soluble in an organic solvent and a charged species is more soluble in aqueous solution.

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49
Q

The _____ is used in place of the partition coefficient K when dealing with a species that has more than one chemical form

A

distribution coefficient D

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50
Q

For an acidic solute, the extraction efficiency is greater at ____ pH levels because _____

A

more acidic
HA is the solute’s predominate form in the aqueous phase

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51
Q

The extraction efficiency is independent of pH for pH levels _____ and essentially zero for pH levels ____

A

independent = more acidic than the HA’s pKa
~zero = more basic than HA’s pKa

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52
Q

the greatest change in extraction efficiency occurs at pH levels where _____

A

both HA and A – are predominant species

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53
Q

Chromatography derived from Greek word ____ and ____

A

chroma means “color”
graphein means “to write”

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54
Q

Chromatography is a separation technique based on the ____ as the compounds travels through a supporting medium

A

different interactions of compounds with two phases, a mobile phase and a stationary phase

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55
Q

General components of chromatography (4)

A

Mobile Phase: a solvent that flows through the supporting medium

Stationary Phase: a layer or coating on the supporting medium that interacts with the analytes

Column: contains the stationary phase, allowing the mobile phase to pass through it

Supporting Medium: solid surface on which the stationary phase is bound or coated

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56
Q

Eluent ___ → Eluate ____

Define both terms

A

Eluent in → Eluate out

Eluent – fluid entering a column
Eluate – fluid exiting the column

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57
Q

the process of passing the mobile phase through the column

A

Elution

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58
Q

solvent used in the elution

A

Eluant

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59
Q

graph showing detector response as a function of a time

A

chromatogram

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60
Q

invented chromatography in 1906 during his research to separate plant pigments like chlorophylls and carotenoids

  • aka father of chromatography
A

Mikhael Tswett

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61
Q

In Column Chromatography,
○ _____ – adsorbent
○ _____ – eluent

A

calcium carbonate – adsorbent
ether/ethanol mixture – eluent

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62
Q

___ Nobel prizes were awarded between 1937 and 1972 alone for work in which chromatography played a vital role.

A

12

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63
Q

The primary division of chromatographic techniques is based on the _____ in the system

A

type of mobile phase used

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64
Q

Two theories explain the phenomenon in chromatography

A

Rate Theory: proposed by Van Deemter in 1956

Plate Theory: developed by Martin and Synge in 1941 (1952 Nobel Prize)

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65
Q

Explain plate theory

A

The theory assumes that the column is divided into a number of zones called theoretical plates

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66
Q

‘imaginary’ measures how efficiency a column can separate a mixture into its components

A

theoretical plates (N)

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67
Q

To achieve efficient separation, theoretical plate (N) must be ____ and the plate height or Height Equivalent of a Theoretical Plate (H or HETP) ______

A

large N
small H

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68
Q

Define rate theory

A

describes the relationship between the height of a theoretical plate (H) and the linear velocity (u) of the mobile phase in chromatography

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69
Q

Sources of Band Broadening (3)

A
  1. Multiple Path in Column
  2. Molecular Diffusion
  3. Mas Transfer
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70
Q

a band of molecules in a chromatographic peak in solvent or gas phase will _____ because of diffusion

A

gradually spread out

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71
Q

the faster we can get the analyte through the column, the ____ will the peak be broadened by the diffusion

A

less

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72
Q

increased ______ velocity increases contribution to spread by resistance to mass transfer

A

mobile phase

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73
Q

Explain the sum of effects of sources of band broadening

A
  1. Multiple path effect is independent of mobile phase velocity
  2. Diffusion effect is inversely proportional to the mobile phase velocity
  3. Mass transfer is proportional to the mobile phase velocity
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74
Q

sum of different variables will obtain _____

A

optimal velocity

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75
Q

the ____ of optimal velocity, the
ideal the mobile phase velocity

A

lowest value

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76
Q

a process that leads to peak (band) broadening due to the presence of multiple flow paths through a packed column

A

Eddy diffusion (uneven flow)
“A” variable in HETP formula

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77
Q

Eddy diffusion is ____ with mobile phase velocity, u

A

independent

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78
Q

Eddy diffusion (A) must be ____ to minimize or have a smaller plate height (HETP)

A

minimized

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79
Q

The degree of band-broadening due to Eddy diffusion and mobile phase mass transfer depends mainly on the (2)

A
  1. diffusion rate of solute
  2. size of packing material
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80
Q

band-broadening due to the diffusion of the solute long the length of the column in the flowing mobile phase

A

Longitudinal diffusion (molecular diffusion)
B variable in HETP equation

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81
Q

longitudinal diffusion (B) is ____ to flow rate (u)

A

inversely proportional

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82
Q

The degree of band-broadening due to longitudinal diffusion depends mainly on the (2):

A
  1. diffusion of solute
  2. flow rate of solute through column
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83
Q

band-broadening due to differences in the rate of diffusion of the solute molecules between the mobile phase outside the pores of the support (flowing mobile phase) to the mobile phase within the pores of the support (stagnant mobile phase)

A

Resistance to Mass Transfer (C)

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84
Q

resistance to mass transfer (C) is ____ with flow rate

A

directly proportional

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85
Q

The degree of band-broadening due to stagnant mobile phase mass transfer depends mainly on the: (3)

A
  1. flow rate of the solute through the column
  2. diffusion and retention of the solute
  3. size, shape, and pore structure of the packing materials
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86
Q

The degree of band-broadening due to stationary phase mass transfer depends mainly on the (3):

A
  1. flow rate of the solute through the column
  2. diffusion and retention of the solute
  3. kinetics of interaction between the solute and stationary phase
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87
Q

The effect of different variables giving the optical velocity is ____

A

Van Deemter plot

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88
Q

information that can be derived from Van Deemter plot is the ______ which has a minimum band-broadening and related to the plate height

A

ideal mobile phase velocity

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89
Q

smaller plate height, ______

A

more ideal mobile phase velocity

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90
Q

How to achieve optimum velocity? (2)

A
  1. Use smaller size packing material
  2. Use uniform size and shape
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91
Q

smaller particles will ____, limiting peak broadening by the multiple path effect (A-term)

A

give more similar paths

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92
Q

smaller particles lead to _____ and therefore reduce the C-term

A

more exchange between the phases

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93
Q

irregularly shaped particles create void volumes that are _____

A

not efficiently flushed by the mobile phase

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94
Q

The _____ is usually not of importance in LC

A

diffusion coefficient (B-term)

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95
Q

time that a solute spends in the stationary and mobile phases

A

Retention time

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96
Q

volume of the mobile phase required to carry the solute through the column to elution

(a measure of the fraction of time spent by
the solute in the mobile phase)

A

retention volume

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97
Q

Retention on a given column pertains to the particulars of that system: column size and flow rate of the mobile phase

A

solute retention

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98
Q

measure of the time the sample component resides in the stationary phase relative to the time it resides in the mobile phase

A

retention factor
(capacity factor)

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99
Q

retention factor is ____ on column length and flowrate and hence, useful for ____

A

comparing results obtained on different systems

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100
Q

way of identifying how good the separation

A

retention factor

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101
Q

k’ < ____, separation is poor
k’ > ____, separation is slow
k’ is ____, separation is optimum

A

k’ < 1.0, separation is poor
k’ > 30, separation is slow
k’ is 2-10, separation is optimum

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102
Q

ability of the chromatographic system to ‘chemically’ distinguish between sample components

A

selectivity factor
(relative retention or separation factor)

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103
Q

selectivity factor is always _____

A

greater than 1

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104
Q

inverse of the ratio of the speeds at which the two components travel

A

unadjusted relative retention

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105
Q

The separation of solutes in chromatography depends on (2)

A
  1. difference in the retention of solutes
  2. sufficiently narrow width of the solute peaks
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106
Q

the farther apart the difference in the retention of solutes, the _____

A

better their separation

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107
Q

the wider the peaks, the _____

A

poorer their separation

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108
Q

How to improve separation? (2)

A
  1. retention factor (k’) is optimized first
  2. selectivity factor (α) is increased
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109
Q

How to increase selectivity factor (α)? (4)

A
  1. changing mobile phase composition
  2. changing column temperature
  3. changing composition of stationary phase
  4. using special chemical effects
    (such as incorporating a species which complexes with one of the solutes into the stationary phase)
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110
Q

another measure of the separation of two peaks of different retention time

A

resolution

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111
Q

____ baseline resolution = ideal/good separation

A

1.5

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112
Q

____ retention, the more prolong/extended time

A

higher retention

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113
Q

____ selectivity, two peaks are far from each other

A

higher selectivity

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114
Q

____ efficiency, there is an overlap in two peaks

A

lower

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115
Q

How to know which column has more theoretical plates?

A

sharper peaks = more efficient separation

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116
Q

How to know which column has larger plate height (HETP)?

A

Broader peaks
large plate height = fewer plates

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117
Q

How to know which column gives higher resolution?

A

less overlap of peaks

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118
Q

How to know which compound has greater retention factor?

A

longer retention time

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119
Q

How to know which compound has greater partition coefficient?

A

longer retention time = greater affinity for stationary phase

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120
Q

How to know the numerical value of unadjusted relative retention?

A

retention time of component 2 / retention time of component 1

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121
Q

Gas-Solid Chrom = solid stationary phase
Gas-Liquid Chrom = ____

A

liquid stationary phase

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122
Q

Gas-solid chromatography uses ____ technique while Gas-Liquid Chromatography uses ____

A

Adsorption chromatography = GSC
Partition chromatography = GLC

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123
Q

Distribution coefficients of compounds are ____ in GSC while ____ in GLC

A

much higher = GSC
comparatively much smaller = GLC

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124
Q

retention time is ____ in GSC while ____ in GLC

A

comparatively long = GSC
comparatively short = GLC

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125
Q

Since liquid phase is absent in GSC, ____ can be used

A

higher temperature

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126
Q

Higher temperature in GLC is determined by the ____

A

nature of liquid phase

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127
Q

Comparatively very small concentration of samples can be used in ____ while higher concentration of samples can be used in ___

A

small conc = GSC
high conc = GLC

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128
Q

most commonly used to separate organic compounds

A

gas-liquid chromatography

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129
Q

for separating species not retained by gas-liquid columns

A

gas-solid chromatography

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130
Q

not much of ____ can be adsorbed on the stationary phase and can be easily removed

A

low molecular weight gases

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131
Q

Describe the instrumentation of Gas Chromatography

A
  1. Carrier Gas Tank
  2. Pressure Regulator
  3. Flow Controller

Inside Column Oven:
4. Sample Injection Port
5. Column
6. Detector

  1. Processor Signal
  2. Outlet
132
Q

inert gas used to carry samples

A

carrier gas

133
Q

carrier gas should be high purity of at least ____. if not, ____ can occur

A

99.995%
interference can occur

134
Q

first choice carrier gas that provides fastest separations due to low molecular weight

A

hydrogen

135
Q

Disadvantages of hydrogen carrier gas

A

flammable and explosive

136
Q

Safer but more expensive option for carrier gas

A

helium

137
Q

Disadvantages of helium carrier gas

A

scarcity

138
Q

carrier gas with smaller diffusion coefficient, slower, relatively higher column efficiency, safe, lower price

A

nitrogen

139
Q

Disadvantages of nitrogen carrier gas

A

low thermal conductivity, poor sensitivity, narrow quantitative linear range, lesser resolution

140
Q

should deliver gas with uniform pressure of flow rate

A

pressure regulatory or flow controller

141
Q

placed before column inlet that has a glass tube with a float held on to a spring

A

rotameter

142
Q

the level of the float of rotameter is determined by the ____

A

flow rate of carrier gas

143
Q

soap bubble formed indicates the flow rate

A

soap bubble flow meter

144
Q

rubber disk with self-sealing rubber

A

septum

145
Q

happened when sample injection system reached its lifespan as observed in sharp repetitive peaks

A

septum bleed

146
Q

Explain sandwich injection

A

Air, solvent, air, sample, air

147
Q

air bubble behind the sample plug ____

A

prevents sample and solvent from mixing

148
Q

Sample injection technique best for thermally unstable solutes and high-boiling solvents; best for quantitative analysis

A

On-Column Injection System

149
Q

Sample injection routine for introducing small sample volume

A

split

150
Q

Sample injection technique best for trace levels of high-boiling solutes in low-boiling solvents

A

Splitless

151
Q

Sample injection that has glass insert whereas the entire sample can be injected into a packed column

A

direct injection

152
Q

sample injected as is by inserting tip of the microsyringe needle directly into the tip of the capillary column, while maintaining injection port temperature below the boiling point of sample solvent (no glass insert)

A

on-column injection

153
Q

injection technique suitable for samples with low concentrations of measurement components

A

on-column

154
Q

Disadvantage of on-column injection

A

periodic maintenance is required (dirty column)

155
Q

injection technique for the analysis of compounds that are thermally unstable and can be done using split or splitless injection

A

Programmed Temperature Vaporization (PTV) Injection

156
Q

In PTV injection, when sample is injected, the injection port is set to _____ of the injection sample solvent

A

below the boiling point

157
Q

after the sample is injected in PTV injection, injection port is _____, causing the injected sample to vaporize

A

heated rapidly

158
Q

Injection technique used if expecting very high concentration of analyte where only a portion is injected into the column and hence, not suitable for trace analysis

A

Split injection

159
Q

injection technique where most of the sample is injected, the remainder is eliminated

A

splitless injection

160
Q

injection technique used for low-concentration samples that require higher sensitivity

A

splitless injection

161
Q

injection technique NOT suitable for gas samples, low boiling point solvent samples, and components eluted in the vicinity of solvents

A

splitless injection

162
Q

Compare the retention time, peak area, and peak width using split and splitless injection

A

Larger and broader retention time, peak area, and peak width in splitless injection

163
Q

Sample introduction techniques (3)

A
  1. solid-phase microextraction
  2. headspace sampling
  3. purge-and-trap
164
Q

If same polarity, the elution will be based on ____

A

order of increasing boiling point

165
Q

Types of column

A
  1. Packed Column
  2. Capillary Column/ Open Tubular
166
Q

In _____, stationary phase is coated directly in the column while in _____ stationary phase is
coated with the inner wall of the column

A

Packed column - directly
Capillary column - inner wall

167
Q

____ column is applicable only for GLC while ____ column is applicable for both GSC and GLC

A

Capillary Column - GLC
Packed Column - GSC and GLC

168
Q

In ____, liquid stationary phase is immobilized on the capillary tubing walls while in _____, liquid stationary phase is adsorbed onto the surface of the beads in a thin layer or onto the solid inert packing

A

Capillary tube - liquid stationary phase is immobilized on the capillary tubing walls

Packed Column - liquid stationary phase is adsorbed onto the surface of the beads in a thin layer or onto the solid inert packing

169
Q

____ column = 2-6 m length, 2-4mm id
____ column = 15-100 m length, 150-300 um id

A

Packed column = 2-6 m length, 2-4mm id
Capillary column = 15-100 m length, 150-300 um id

170
Q

____ column = will require a higher flow rate (25 - 150 mm per min)
____ column = flow rate under 25 mm per min

A

Packed column = will require a higher flow rate (25 - 150 mm per min)
Capillary column = flow rate under 25 mm per min

171
Q

made up of stainless steel or glass tube filled with particulate packing material (an adsorbent material, or a support material coated or impregnated with a solid phase)

A

Packed Column

172
Q

solid support of packed column is often ___ that is ____ to reduce hydrogen bonding to polar solutes

A

silica that is silanized

173
Q

compared with open tubular columns, packed columns provide ____ capacity but give ____, ______, and ______

A

greater sample
broader peaks, longer retention times, and less resolution

174
Q

long narrow open tubular columns that are made of fused silica (SiO2) and coated with polyimide (a plastic capable of withstanding 350°C) for support and protection from atmospheric moisture

A

capillary column

175
Q

compared with packed columns, capillary column offers ____, ____, and ____ but ____

A

higher resolution
shorter analysis time
greater sensitivity
lower sample capacity

176
Q

Types of Capillary Column

A
  1. Wall Coated Open Tubular Column (WCOT)
    - has 0.1 to 5 um thick film of stationary liquid phase on the inner wall of the column
  2. Porous Layer Open Tubular Column (PLOT)
    - porous layer (solid particles and liquid coat), such as fused silica, coated onto the column wall
  3. Support Coated Open Tubular Column (SCOT)
    - has solid particles coated with a stationary liquid phase
  4. Fused Silica Open Tubular Column (FSOT)
    - stationary phase is chemically bonded (still has liquid layer) onto the column wall
177
Q

In ____ programming, constant oven temperature is used while in ____ programming, it will start at low temperature then gradually ramp to higher temperature

A

Isothermal - constant oven temperature
Gradient - start at low temperature then gradually ramp to higher temperature

178
Q

Raising column temperature will (2):

A
  1. decreases retention time
  2. sharpen peaks
179
Q

a precaution to maintain the life of actual column

A

Guard Column

180
Q

used to accumulate and remove non-volatile
substances that would otherwise contaminate (can permanently adhere) the chromatography column and degrade its performance

A

guard column

181
Q

Guard column can be ____ since it is replaceable and cheaper

It should be trimmed _____ off, when irregular peaks shapes from a column that had been producing symmetric peaks suddenly appear

A

cut; 10-20 cm

182
Q

allows solvent to evaporate prior to entering the chromatography column (separate solvent from solute) to improve peak shapes under certain conditions

A

retention gap

183
Q

Desirable properties for the immobilized liquid phase in GLC column (4)

A
  1. low volatility
  2. thermal stability
  3. chemical inertness
  4. solvent characteristics fall within a suitable range
184
Q

Gas chromatographic stationary phases often _____ to _____

A

bonded and cross-linked
provide longer lasting stationary phase

185
Q

Detector must be maintained at ____ than the column so analyte will be gaseous

A

higher temperature

186
Q

Types of Detectors (8)

A
  1. Flame ionization Detector (FID)
  2. Thermal Conductivity Detector (TCD)
  3. Electron Capture Detector (ECD)
  4. Nitrogen Phosphorus Detector (NPD)
  5. Sulfur Chemiluminescence Detector (SCD)
  6. Flame Photometric Detector (FPD)
  7. Photoionization Detector (PID)
  8. Electrolytic Conductivity Detector (ELCD)
187
Q

Detector for compounds with C-H bonds

A

Flame ionization Detector (FID)

188
Q

Detector used for all compounds except for the carrier gas (Hydrogen, Helium, and Nitrogen)

A

Thermal Conductivity Detector (TCD)

189
Q

Detector for halogens, nitrates and conjugated carbonyls (pesticides)

A

Electron Capture Detector (ECD)

190
Q

ECD used ____ foil lining the detector cell

A

Ni-63

191
Q

Detector for nitrogen and phosphorus containing compounds

A

Nitrogen Phosphorus Detector (NPD)

192
Q

Detector for sulfur containing compounds

A

Sulfur Chemiluminescence Detector (SCD)

193
Q

Detector for sulfur or phosphorus containing compounds (only one at a time)

A

Flame Photometric Detector (FPD)

194
Q

Detector for aromatics and olefins

A

Photoionization Detector (PID)

195
Q

Detector for halogens, sulfur or nitrogen containing compounds (only one at a time)

A

Electrolytic Conductivity Detector (ELCD)

196
Q

First to be eluted - ____ boiling point

A

lowest

197
Q

Qualitative analysis can detect compounds ____

A

with boiling point up to 400°C

198
Q

Qualitative analysis ___ detect compounds that are not decomposed at their vaporization temperature but ___ detect highly adsorptive compounds

A

can detect compounds that are not decomposed at their vaporization temperature

cannot detect highly adsorptive compounds

199
Q

Qualitative analysis cannot detect ____ compounds and chemically ____ compound

A

highly reactive and chemically unstable

200
Q

Qualitative analysis ___ detect compounds that decompose at their vaporization temperature, but always by the same amount solid inert packing

A

can detect

201
Q

When analyzed under the same conditions, the same component ______

A

always elutes at the same time

202
Q

______ components should be separated, since peaks can overlap with each other and may affect the confirmation of standard

A

all components

203
Q

a number, obtained by interpolation (usually logarithmic), relating the adjusted retention time (volume) or the retention time (volume) or the retention factor of the sample component to the adjusted retention times (volumes) of the two standards eluted before and after the peak of the sample component

A

retention index/ Kovats retention index

204
Q

used as a second characteristic to reduce false matches but not a sole tool to give specific component

A

retention index

205
Q

Retention index usually used ____as standard and applicable to ____

A

normal alkanes
hydrocarbons

206
Q

Lowest retention index _____ to elute

A

first

207
Q

Given a polar stationary phase, what will be the elution order?

A

Least polar (non-polar) will elute first

208
Q

use a separate standard and compare with the unknown

A

External Standard Calibration

209
Q

use a separate standard similar in properties with the unknown and you run them together

A

Internal Standard Method

210
Q

spike your sample with the same standard

A

Standard Addition Method

211
Q

area of each peak is measured and corrected for differences in detector responses to the different eluates.

A

Peak area method (are normalization method)

212
Q

similar to external standard but it does not require a separate standard.

A

Peak integration

213
Q

introduces the relative sensitivity of the component

A

Corrected Peak Are Method

214
Q

Explain traditional liquid chromatography

A

Good separation and reasonable flow rate but VERY LONG separation

215
Q

High Pressure Liquid Chromatography has a ___ (4)

A

good system
small plate heights
narrow peaks
shorter separation times

216
Q

if lower particle size than HPLC, ____ is used

A

UPLC (ultra performance LC)

217
Q

Advantage of HPLC (2)

A
  1. can accommodate non-volatile and thermally unstable compounds
  2. applicable to inorganic ions
218
Q

HPLC Instrumentation (7)

A
  1. Mobile Phase
  2. Degassing Unit
  3. Solvent Delivery Pump
  4. Injector and Sample Vial
  5. Column and Column Oven
  6. Detector
  7. Workstation
219
Q

Remove dissolved air from mobile phase

A

degassing unit

220
Q

Deliver the mobile phase at constant flow

A

solvent delivery pump

221
Q

Introduce standard solution or real sample to HPLC column

A

Injector

222
Q

Store standard solution or sample solution

A

Sample Vial

223
Q

Separate each compound contained in the sample

A

Column

224
Q

Keep temperature constant

A

Column oven

225
Q

Detect eluted compounds from column

A

Detector

226
Q

Signal from detector is processed and chromatogram is displayed

A

Workstation

227
Q

____ solvents are required as HPLC mobile phase

A

Ultra-pure HPLC-grade

228
Q

Impurities from mobile phase can ____ the column and ___ with detector

A

degrade
interfere

229
Q

Solvent should be ___ and ____

A

filtered and degassed

230
Q

Dissolved air in solvent may lead to ____ and dissolved O2 would ____

A

unstable flow rate

absorb UV radiation which would interfere with the spectrophotometric detector

231
Q

Microfiltration membrane for organic compounds

A

Teflon

232
Q

Microfiltration membrane for aqueous solutions

A

cellulose

233
Q

Microfiltration membrane for organic and aqueous solution

A

nylon

234
Q

Degassing techniques (4)

A
  1. Vacuum pumping
  2. Heating and stirring
  3. ultrasonicating
  4. sparging
235
Q

uses inert gas that is not soluble in the mobile phase to remove dissolved gases

A

sparging

236
Q

Modes of solvent delivery (2)

A
  1. Isocratic Elution - single solvent
  2. Gradient Elution (solvent programming) - 2 or more solvents
237
Q

mode of solvent delivery where solvents are mixed BEFORE ELUTION

A

isocratic elution

238
Q

mode of solvent delivery where solvents are mixed DURING ELUTION

A

gradient elution (solvent programming)

239
Q

In gradient elution, it uses 2 or more solvent systems that have ____

A

different polarity

240
Q

Gradient elution can be used to elute compounds that were _____ on the column

A

“stuck”

241
Q

In gradient elution, column has to be ____ after each run because the mobile phase is varied

A

re-equilibrate

242
Q

Advantages of gradient elution (4)

A
  1. provides equal bandwidths
  2. fast overall separation
  3. maximum resolution
  4. maximum sensitivity
243
Q

supply the force necessary to move the mobile phase with a constant flow rate and should generate high pressure

A

pump system

244
Q

simplest pump available for HPLC that uses motorized syringe to get a constant solvent delivery

A

Syringe Pump

245
Q

In using syringe pump, large volume of sample is _____ and has ____ solvent capacity

A

not required
limited solvent capacity

246
Q

has small chamber in which the eluent is pumped by the movement of a motor-driven pistol

A

Single Piston Pump

247
Q

ensures that eluent will not come back to the chamber

A

inlet check valve

248
Q

Disadvantage of single piston pump

A

not constant flow rate

249
Q

uses second motor to improve consistency of flow rate use; while one piston is sucking the second motor will release

A

parallel reciprocating pump

250
Q

has two motors but has single check valve

A

series reciprocating pump

251
Q

provides pulse free output but inexpensive and depends on solvent viscosity and back pressure

A

gradient pump

252
Q

different pump is used for each solvent and the eluent composition is determined by the relative flow rate of each pump

A

binary pump (high pressure mixing)

253
Q

has one pump but with 4 valves. Eluent composition can be modified depending on which valve is opened

A

quaternary pump

254
Q

introduces a small sample (0.-100µL) without depressurization

A

manual injection

255
Q

mobile phase bypasses the sample loop and flows directly into the column

A

load position

256
Q

mobile phase back flushes the sample from loop into the column

A

inject position

257
Q

produce sample into high pressure mobile phase flow without an interruption to the flow

A

automatic injection (autosampler)

258
Q

park the sample in a sample loop while the flow is maintained through the column

A

Sampling Valve

259
Q

rotates as the sample is introduced into the high pressure system

A

switching valve

260
Q

protects the analytical column by removing particulate matter and contamination that might bind to the stationary phase

A

guard column

261
Q

column that is made up of tightly packed material; longer than guard column

A

analytical column

262
Q

_____ the column can decrease retention time and improve resolution

A

heating

263
Q

Property of analytical column that is for the high-pressure resistance (20,000 psi) and expensive

A

stainless steel

264
Q

Cheaper alternative for stainless steel analytical column

A

heavy-wall glass

265
Q

Property of analytical column that is less pressure (< 600 psi) tolerant but highly resistant to thermal degradation and can easily be cut

A

PEEK (poly ether ether ketone) Tubing

266
Q

Property of analytical column that has high speed and minimum solvent consumption. shorter in length and larger in number of plates

A

Microcolumn

267
Q

Property of analytical column that separates
components of a mixture and collects isolated components, and non-destructive of the sample

A

Preparative column

268
Q

Detector selectivity is ____ important in liquid chromatography than in GC

A

more

269
Q

Disadvantages of liquid chromatography

A

more band broadening and more broad peaks

270
Q

measures property of mobile phase with or without solute.

A

Bulk Property (Universal Detector)

271
Q

Bulk property (universal detector) will____ since it is dependent on the mobile phase

A

not detect if it is an impurity or solute

272
Q

measures the difference between refractive index between column eluent and reference stream of pure solvent

A

refractive index detector

273
Q

refractive index detector ____ in gradient elution

A

useless

274
Q

detection is based on the scattering of a beam of light by particles of compound remaining after evaporation of mobile phase

A

Evaporative Light Scattering Detector

275
Q

Evaporative Light Scattering Detector ___ all analyte

Refractive Index Detector ____ to all analyte

A

Evaporative Light Scattering Detector detects all analyte

Refractive Index Detector responds to all analyte

276
Q

measures property of mobile phase without the solute and will depend on the property of solute

A

solute property (selective detector)

277
Q

most common method that is used to detect sample components which have chromophores that will absorb UV or visible light

A

UV-Vis Absorbance Detector

278
Q

very sensitivity detector that is used for sample with fluorescing species

A

fluorescence detector

279
Q

detection is based on amperometry, polarography, coulometry which is used to detect electrochemically active species that are easily oxidized/reduced

A

electrochemical detector

280
Q

used for ionic compounds that measures electrical resistance which is directly proportional to concentration of ions in the solution

A

Conductivity Detector

281
Q

Detector for optically active compounds

A

Optical Rotation Detector

282
Q

measures the angle of rotation of polarized light caused by an optical active isomer

A

polarimetry

283
Q

Polarimetry is useful for _____ compounds with no absoprtion

A

chiral

284
Q

based on difference in refractive index (solute)

A

Optical Rotatory Dispersion (ORD)

285
Q

differentiate enantiomers by measuring difference between the absorption of right and left-handed circulatory polarized light due to the existence of a chiral chromophore

A

Circular Dichroism (CD)

286
Q

converts analytes to a charged state on the basis of their mass to charge ratio and used when there is no standard

A

Mass Spectrometry Detector

287
Q

if refractive index and UV-vis absorbance are used at the same time, _____ can be detected and analyzed

A

almost ALL components

288
Q

What to do when column deteriorate?

A

check if the column exceeded its lifespan

289
Q

What to do when inappropriate sample solvent or injection volume is applied?

A

reduce sample volume

290
Q

The cause of dead volume in the flow lines

A

irregular flow of the mobile phase due to gas particles in the solvent

291
Q

Classification of HPLC where separation is based on polarities and the stationary phase is liquid which is immiscible with the liquid mobile phase

A

Partition Chromatography

292
Q

liquid is held in place by physical absorption

A

Liquid-liquid Partition Chromatography

293
Q

liquid is attached by chemical bonding

A

Liquid-bonded Phase Chromatography

294
Q

type of partition HPLC which has polar analyte, polar stationary phase, non-polar mobile phase

A

Normal Phase Chromatography (NPC)

295
Q

R groups used to modify the polarity of the stationary phase in NPC (3)

A
  1. R=cyano (least polar)
  2. amino
  3. diol
296
Q

In NPC, increasing polarity of mobile phase will ____ while in RPC, increasing polarity of mobile phase will _____

A

NPC: decrease elution time
RPC: increase elution time

297
Q

In NPC, ____ polar will be eluted first while in RPC, ____ polar will be eluted first

A

NPC: least polar
RPC: most polar

298
Q

Type of partition HPLC which has non-polar analyte, non-polar stationary phase, polar mobile phase

A

Reverse Phase Chromatography (RPC)

299
Q

R group of the stationary phase in RPC (3)

A

All non-polar
1. C8 (n-octyl)
2. C12 (n-dodecyl)
3. C18 (n-octadecyl)

300
Q

Analyte polarity trend

A

Hydrocarbon < ethers < esters < ketones < aldehydes < amines < alcohols < salts

301
Q

Mobile Phase Polarity trend

A

water > methanol > ethanol > acetonitrile > tetrahydrofuran > propanol > cyclohexane > hexane

302
Q

Stationary Phase Polarity Trend

A

Silica > CN > C8 > C18

303
Q

if %v/v of methanol is increased then its polarity ____ thus retention factor also ____

A

decreases
decreases (shorter retention time)

304
Q

separation of relatively polar, water soluble organic compound w/ MW<5000

A

adsorption chromatography

305
Q

In adsorption chromatography, stationary phase is a ____ and mobile phase is ____

A

stationary phase is a polar solid (silica or alumina)

mobile phase is non-polar liquid (single or mixture solvent)

306
Q

measure of the solvent absorption energy

A

eluent strength

307
Q

more polar, _____ eluent strength, the ____ will solutes be eluted from the column

A

more polar, greater eluent strength, the more rapidly will solutes be eluted from the column

308
Q

In RPC, eluent strength increases as polarity of solvent _____ while in NPC, increase in eluent strength as solvent becomes ____

A

decrease
more polar

309
Q

used to separate molecules of different molecular sized and shapes

A

Size exclusion chromatography
molecular exclusion
molecular sieve chromatography

310
Q

size exclusion chromatography for polar water-soluble compounds

A

gel filtration

311
Q

size exclusion chromatography for nonpolar compounds

A

gel permeation

312
Q

In size exclusion chromatography, ____ molecules will elute first

A

large

313
Q

subset of reverse phase chromatography in which ionizable species are separated on reverse-phase columns

A

ion-pair chromatography

314
Q

mixture of similar charged ions (polar molecules) separated using ion exchange resin

A

ion-exchange chromatography

315
Q

has a separate suppressor column after the analytical column

A

Suppressor-based/ suppressed ion chromatography

316
Q

ion exchange chromatography for
separation of negatively charged molecules

A

anion exchange chromatography

317
Q

ion exchange chromatography for
separation of positively charged molecules

A

cation exchange chromatography

318
Q

In anion exchange chromatography, stationary phase is ____ charged while in cation exchange chromatography, stationary phase is _____ charged.

A

anion exchange chromatography: positively charged stationary phase

cation exchange chromatography: negatively charged stationary phase

319
Q

organic polymer with porous structure

A

ion exhcnage resin

320
Q

polyvalent ions are ____ held by the stationary phase than singly charge species

A

much more strongly

321
Q

If same charge, _____ molecules will elute first

A

smaller

322
Q

Ion exchange capacity is dependent on the _____

A

total number of ion active groups

323
Q

most specific chromatography with very high selectivity and resolution which is used for separation of biochemical mixtures based on a highly specific interaction between pairs of biological materials

A

Affinity chromatography

324
Q

sample is reacted with another reagent to make it compatible with the separation method

A

sample derivatization

325
Q
A

Analytical Chemistry (12 decks)

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