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CHEM 128 2ND > Mixed 3 > Flashcards

Mixed 3 Flashcards

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1
Q

What does i.d. stand for in the context of column dimensions in preparative HPLC?

A

Internal diameter

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2
Q

In preparative HPLC, column dimensions are dictated by the amount of __________ per injection.

A

material

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3
Q

Which mobile phase characteristic is important for low column back pressure?
a) UV transparency
b) Viscosity
c) Volatility
d) Purity

A

b) Viscosity

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4
Q

Name a factor influencing the choice of mobile phase in preparative HPLC.

A

Spectroscopic characteristics (e.g., UV transparency, fluorescence properties)

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5
Q

For compounds with poor solubility in the mobile phase, __________ overloading is used in preparative HPLC.

A

volume

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6
Q

Which particle size is typically used for well-resolved samples in preparative HPLC?
a) 1.8-μm
b) 3.5-μm
c) 5-μm
d) 7-μm and 10-μm

A

d) 7-μm and 10-μm

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7
Q

What effect does concentration overloading have on the peak shape in preparative HPLC?

A

The peak shape changes from a Gaussian curve to a triangle.

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8
Q

The __________ of the mobile phase should have good solubility properties for maximum sample loads in preparative HPLC.

A

solvent

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9
Q

Which type of overloading allows the separation of samples in the milligram range even on analytical columns?
a) Concentration overloading
b) Volume overloading
c) Pressure overloading
d) Temperature overloading

A

a) Concentration overloading

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10
Q

What is the typical particle size used in analytical columns that is generally not used in larger scale preparative columns?

A

1.8- and 3.5-μm particles

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11
Q

In preparative HPLC, the capacity factor k’ __________ when concentration overloading occurs.

A

decreases

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12
Q

Which mobile phase characteristic is important for easy removal from isolated fractions?
a) Viscosity
b) Volatility
c) Purity
d) Cost

A

b) Volatility

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13
Q

What is the primary objective of analytical HPLC compared to preparative HPLC?

A

The quantitative and/or qualitative determination of a compound.

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14
Q

In preparative HPLC, larger column diameters and __________ flow rates are typically used.

A

higher

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15
Q

What is the effect of non-linear adsorption isotherms in preparative HPLC?
a) Improved peak symmetry
b) Strong tailing of peaks
c) Increased capacity factor
d) Reduced resolution

A

b) Strong tailing of peaks

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16
Q

What type of columns are generally not economical for separating small amounts of compound?

A

Large columns

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17
Q

The __________ of preparative HPLC columns is determined by the selectivity (α) of the column.

A

sample capacity

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18
Q

Which characteristic of the mobile phase is important for low levels of non-volatile contaminants?
a) UV transparency
b) Fluorescence properties
c) Purity
d) Solubility

A

c) Purity

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19
Q

Which of the following is the primary purpose of preparative HPLC?
a) Analyzing small sample quantities
b) Purifying large quantities of substances
c) Quantifying chemical concentrations
d) Calibrating laboratory equipment

A

b) Purifying large quantities of substances

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20
Q

Identify the component labeled as “detector” in the preparative HPLC setup diagram. What does it do?

A

The detector is responsible for identifying and quantifying the separated components as they elute from the column.

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21
Q

The __________ is the part of the HPLC system where the separation of compounds occurs.

A

column

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22
Q

Which solvent is typically used for conditioning the column in HPLC?
a) Water
b) Methanol
c) Acetone
d) Hexane

A

b) Methanol

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23
Q

In preparative HPLC, the mobile phase moves through the column and carries the __________ with it.

A

sample

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24
Q

What is a common elution method in HPLC?
a) Isocratic
b) Gradient
c) Both a and b
d) Neither a nor b

A

c) Both a and b

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25
Q

Identify the polarity of the SP and MP used in reversed-phase HPLC.

A

The stationary phase is nonpolar, and the mobile phase is polar.

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26
Q

The role of the __________ in HPLC is to separate the analytes based on their interactions with the stationary phase.

A

column

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27
Q

What is the primary principle behind Solid Phase Extraction (SPE)?
a) Melting point differences
b) Solubility differences
c) Affinity differences
d) Boiling point differences

A

c) Affinity differences

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28
Q

Identify the interaction primarily used in reversed-phase SPE.

A

Nonpolar-nonpolar interactions (hydrophobic interactions).

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29
Q

In SPE, __________ is often used to wet and activate the packing bed.

A

Methanol

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30
Q

Which material is used for strong anion exchange in SPE?
a) Cyanopropyl bonded silica
b) Quaternary amine bonded silica
c) Sulfonic acid bonded silica
d) Carboxylic acid bonded silica

A

b) Quaternary amine bonded silica

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31
Q

The __________ step in SPE involves passing the sample slowly through the cartridge to ensure interaction with the media.

A

loading

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32
Q

What is the main application of SPE?
a) Sample cleanup
b) Chemical synthesis
c) Molecular cloning
d) DNA sequencing

A

a) Sample cleanup

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33
Q

Identify the solvent typically used in normal phase SPE.

A

Nonpolar solvents like hexane or chlorinated solvents.

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34
Q

The SPE material, __________, is used for weak cation exchange of cations and amines.

A

carboxylic acid bonded silica

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35
Q

Which mode of separation in SPE is based on electrostatic attraction?
a) Reversed Phase
b) Normal Phase
c) Ion Exchange
d) Adsorption

A

c) Ion Exchange

36
Q

Identify one application of Octadecyl bonded (C18) material in SPE.

A

Extraction of nonpolar to moderately polar compounds such as barbiturates or pesticides.

37
Q

In SPE, __________ interactions are used in the normal phase for separating polar compounds.

A

hydrophilic

38
Q

Which of the following is a step in the SPE process?
a) Drying the sample
b) Washing the cartridge
c) Freezing the sample
d) Heating the column

A

b) Washing the cartridge

39
Q

Identify a common pretreatment for biological matrices like serum or plasma in SPE.

A

Shift pH of the sample to extremes or precipitate proteins using solvents like acetonitrile.

40
Q

During SPE, the __________ step involves using an appropriate solvent to remove the compounds of interest from the cartridge.

A

elution

41
Q

What is the role of pH in ion exchange SPE?
a) It affects the solubility of the analyte.
b) It ensures the analyte and the functional groups on the silica surface are oppositely charged.
c) It stabilizes the column temperature.
d) It modifies the viscosity of the solvent.

A

b) It ensures the analyte and the functional groups on the silica surface are oppositely charged.

42
Q

Identify the common sample pretreatment for water samples in SPE.

A

Direct extraction if not heavily laden with solids, or filtration if necessary.

43
Q

In reversed-phase SPE, a sample with high alcohol content may require __________ with water or buffer.

A

dilution

44
Q

Which material is used in SPE for the normal phase extraction of polar compounds?
a) Octyl bonded (C8)
b) Diol bonded
c) Quaternary amine bonded silica
d) Carboxylic acid bonded silica

A

b) Diol bonded

45
Q

Identify the primary benefit of SPE in analytical procedures.

A

Versatility, selectivity, speed, and low solvent usage.

46
Q

__________ is used to precipitate proteins in biological samples before SPE.

A

Acetonitrile (or methanol, acetone)

47
Q

What is a common use of sulfonic acid bonded silica in SPE?
a) Strong anion exchange
b) Strong cation exchange
c) Normal phase extraction
d) Adsorption

A

b) Strong cation exchange

48
Q

Identify the step in SPE where the sample is added to the cartridge at a slow rate.

A

Loading the sample

49
Q

What is the typical carrier gas used in gas chromatography?
A. Oxygen
B. Helium
C. Carbon dioxide
D. Methane

A

B. Helium

50
Q

The area under the curve in a gas chromatogram is proportional to the _____ of the compound adsorbed to the stationary phase.

A

mass/concentration

51
Q

What type of detector responds to compounds that produce ions when burned in an H2-air flame?

A

Flame Ionization Detector (FID)

52
Q

Which of the following compounds would NOT be detected by a Flame Ionization Detector (FID)?
A. Benzene
B. Toluene
C. Carbon dioxide
D. Ethylbenzene

A

C. Carbon dioxide

53
Q

What is the principle behind capillary electrophoresis?

A

Electrophoresis - The differential movement or migration of ions by attraction or repulsion in an electric field.

54
Q

True or False: The Thermal Conductivity Detector (TCD) is ideal for detecting halogenated organic compounds.

A

False

55
Q

Which of the following molecules CANNOT be separated by capillary electrophoresis?
A. Proteins
B. Amino acids
C. Inorganic ions
D. Large polymers

A

D. Large polymers

56
Q

The speed of movement or migration of solutes in CE is determined by their _____ and _____.

A

charge, size

57
Q

True or False: Capillary electrophoresis can be used for preparative-scale separations.

A

False

58
Q

Which mode of CE involves the use of surfactants to form micelles?

A

Micellar electrokinetic capillary chromatography (MEKC)

59
Q

The velocity of a compound through the GC column depends upon its _____ for the stationary phase.

A

affinity

60
Q

Which of the following detectors is specific for halogenated organic compounds?
A. Flame Ionization Detector (FID)
B. Thermal Conductivity Detector (TCD)
C. Electron Capture Detector (ECD)
D. Mass Spectrometer (MS)

A

C. Electron Capture Detector (ECD)

61
Q

True or False: Gas chromatography requires large sample volumes for analysis.

A

False

62
Q

In gas chromatography, the _____ column is best for speed and efficiency but can only handle small samples.

A

Capillary/Open Tubular

63
Q

What is the basis of electrophoretic separations in CE?

A

The migration velocity and electrophoretic mobility of charged particles in an electric field.

64
Q

True or False: The flow profile of electroosmotic flow (EOF) contributes significantly to band broadening in CE.

A

False

65
Q

Which of the following factors can be used to control the electroosmotic flow (EOF) in CE?
A. Electric field
B. Buffer pH
C. Ionic strength
D. All of the above

A

D. All of the above

66
Q

In CE, the _____ term in the Van Deemter equation is absent due to the open tubular capillary used.

A

A term (multipath)

67
Q

Identify the mode of CE that uses a polymeric gel matrix in the capillary to separate molecules based on their size.

A

Capillary gel electrophoresis (CGE)

68
Q

What is the purpose of the carrier gas in gas chromatography?
A. To elute the sample components from the column
B. To provide the mobile phase for separation
C. To carry the sample components through the column
D. Both B and C

A

D. Both B and C

69
Q

True or False: The Flame Ionization Detector (FID) has a linear response over a wide range of concentrations.

A

True

70
Q

The _____ detector is ideal for detecting permanent gases like H2, N2, O2, and CO2.

A

Thermal Conductivity Detector (TCD)

71
Q

Which of the following statements about packed columns in GC is true?
A. They are best for large-scale separations
B. They are more efficient than capillary columns
C. They are slower and less efficient than capillary columns
D. They are used for separating gases only

A

C. They are slower and less efficient than capillary columns

72
Q

What is the purpose of the oven in a gas chromatograph?
A. To control the temperature of the column
B. To heat the carrier gas
C. To maintain the sample in the vapor phase
D. Both A and C

A

D. Both A and C

73
Q

True or False: Mass spectrometers can provide structural information about compounds separated by GC.

A

True

74
Q

In gas chromatography, the _____ detector is suitable for detecting halogenated organic compounds.

A

Electron Capture Detector (ECD)

75
Q

Which of the following statements about the Flame Ionization Detector (FID) is true?
A. It responds to all organic compounds
B. It has a non-linear response over a wide range of concentrations
C. It is ideal for detecting permanent gases
D. It has a limited dynamic range

A

A. It responds to all organic compounds

76
Q

What is the principle behind electroosmotic flow (EOF) in CE?
A. The movement of cations towards the cathode
B. The movement of anions towards the anode
C. The bulk flow of the buffer solution due to the charge on the capillary wall
D. The separation of molecules based on their charge-to-mass ratio

A

C. The bulk flow of the buffer solution due to the charge on the capillary wall

77
Q

True or False: In CE, neutrals move towards the anode due to the electroosmotic flow.

A

False

78
Q

Which of the following modes of CE involves the use of a polymeric gel matrix in the capillary?
A. Capillary zone electrophoresis (CZE)
B. Capillary electrochromatography (CEC)
C. Capillary gel electrophoresis (CGE)
D. Micellar electrokinetic capillary chromatography (MEKC)

A

C. Capillary gel electrophoresis (CGE)

79
Q

In CZE, the separation relies principally on the pH-controlled _____ of acidic groups on the solute or the _____ of basic functions on the solute.

A

dissociation, protonation

80
Q

Identify the mode of CE that combines the high separation efficiency of CZE with the selectivity of HPLC.

A

Capillary electrochromatography (CEC)

81
Q

True or False: In MEKC, the separation principle is based on the differential partition of analytes between the micelle and the solvent.

A

True

82
Q

Which of the following statements about CEC is true?
A. It uses hydraulic pressure to propel the mobile phase
B. It has minimal backpressure, allowing the use of small-diameter packings
C. It cannot achieve high separation efficiencies
D. It is limited to separating only charged species

A

B. It has minimal backpressure, allowing the use of small-diameter packings

83
Q

In MEKC, the _____ causes the negatively charged micelles to flow slower than the bulk flow (endoosmotic flow)

A

voltage

84
Q

Identify the mode of CE that separates molecules based on their isoelectric point.

A

Capillary isoelectric focusing (CIEF)

85
Q

True or False: In CZE, the separation of analytes relies on their differences in charge and size.

A

True

CHEM 128 2ND (6 decks)

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