Deck 3: Chromatography and Mass Spectrometry: Theory, Practice, and Instrumentation

Question 1

Chromatographic attractive forces forming between two molecules with formal positive and negative charges are known as:

A)dispersive (van der Waals) forces
B)dipolar forces
C)hydrogen bonding forces
D)dielectric forces

Answer 1

dielectric forces

Question 2

Chromatographic attractive forces that result from one molecule inducing a temporary separation of charges in an adjacent molecule are known as:

A)dispersive (van der Waals) forces
B)dipolar forces
C)hydrogen bonding forces
D)dielectric forces

Answer 2

dispersive (van der Waals) forces

Question 3

Given the following data, calculate the resolution between the two solutes.
Peak A: peak begins at 1.40 minutes
Peak maximum occurs at 1.45 minutes
Peak returns to baseline at 1.50 minutes
Absorbance at peak maximum is 1.200
Peak B: peak begins at 1.55 minutes
Peak maximum occurs at 1.65 minutes
Peak returns to baseline at 1.75 minutes
Absorbance at peak maximum is 0.475

A)0.67
B)1.33
C)2.0
D)4.0

Answer 3

1.33

Question 4

Chromatographic attractive forces involving molecules that have a permanent dipole are known as:

A)dispersive (van der Waals) forces
B)dipolar forces
C)hydrogen bonding forces
D)dielectric forces

Question 5

The desired resolution for good quantitative or qualitative chromatographic analysis is ______ or greater.

A)0.4
B)0.8
C)1.0
D)1.25

Question 6

Chromatography is best characterized as a separation technique in which the components of a mixture are separated based on:

A)how the components distribute between the mobile phase and stationary phase
B)how well the components dissolve in the mobile phase
C)the chromophoric nature of the components
D)the varying concentrations of the components

Question 7

Considering the chromatographic separation of two solutes that are present in a mixture at the same concentration and produce the same detector response (i.e., have the same molar absorptivity), the solute that has a higher affinity for the stationary phase will have a ______ retention time and a ______ detector response than the solute that has a higher affinity for the mobile phase.

A)greater, greater
B)lesser, greater
C)greater, lesser
D)lesser, lesser

Question 8

Chromatographic attractive forces resulting when the small atom size approaches very close to the negative end of a dipole are known as:

A)dispersive (van der Waals) forces
B)dipolar forces
C)hydrogen bonding forces
D)dielectric forces

Question 9

The type of chromatography in which separation occurs by differential distribution of solutes between two immiscible liquids is known as:

A)adsorption chromatography
B)partition chromatography
C)ion-exchange chromatography
D)gel-permeation chromatography

Question 10

In reversed-phase chromatography, the mobile phase is relatively ______, and the stationary phase is relatively ______.______ solute molecules are least retained in this type of chromatography.

A)polar, nonpolar, polar
B)polar, nonpolar, nonpolar
C)nonpolar, polar, polar
D)nonpolar, polar, nonpolar

Question 11

What is the correct interpretation of column selectivity (α) = 1.0?

A)The separation of the solutes has been optimized, and no further improvement can be made in chromatographic conditions.
B)The solutes are adequately separated by the chromatographic system.
C)The solutes are partially separated by the chromatographic system.
D)The solutes are not separated by the chromatographic system.

Question 12

Which of the following molecular characteristics forms the basis for chromatographic retention in adsorption and partition chromatography?

A)molecular size and shape
B)polarity
C)molar absorptivity
D)all of the above

Question 13

Suppose drug A and drug B are to be separated by anion-exchange chromatography.Drug A is an acid with a pKₐ of 8.0, and drug B is an acid with a pKₐ of 4.0.Following the proper steps to place the mixture of drugs onto the anion-exchange phase, the pH of the mobile phase should be adjusted to ______ to elute drug A only.Then the pH of the mobile phase should be adjusted to _____ to elute drug B from the stationary phase.

A)4.0, 8.0
B)8.0, 4.0
C)10.0, 6.0
D)6.0, 2.0

Question 14

Chromatographic methods may be characterized according to:

A)the physical state of the mobile phase
B)the physical apparatus associated with the stationary phase
C)the mechanism of separation
D)all of the above

Question 15

Given the following data, calculate the column selectivity (α).
Chart speed for recording the chromatogram is 1 cm/min
Mobile phase flow rate is 1.6 mL/min
Migration distance of the void volume indicator is 1.3 cm
Migration distance of the first solute of interest is 14.8 cm
Migration distance of the second solute of interest is 15.8 cm

A)0.93
B)1.07
C)10.38
D)11.15

Question 16

In normal-phase chromatography, the mobile phase is relatively ______, and the stationary phase is relatively ______._____ solute molecules are retained the longest in this type of chromatography.

A)polar, nonpolar, polar
B)polar, nonpolar, nonpolar
C)nonpolar, polar, polar
D)nonpolar, polar, nonpolar

Question 17

Given the following data, calculate the capacity factor for the solute.
Chart speed for recording the chromatogram is 1 cm/min
Mobile phase flow rate is 1.6 mL/min
Migration distance of the void volume indicator is 1.3 cm
Migration distance of the solute of interest is 13.2 cm

A)2.08
B)9.15
C)21.12
D)Cannot determine from data provided

Question 18

Which of the following steps could be taken to improve column selectivity (α)?

A)Change the volume of the sample analyzed.
B)Change the mobile phase flow rate.
C)Change the composition of the stationary phase.
D)All of the above.

Question 19

Given that adsorption chromatography is being utilized with a polar adsorbent such as silica, predict the order of elution of the following three compounds with the first to elute being listed first.
Compound A - nonpolar compound with minimal potential for hydrogen bonding
Compound B - polar compound with intermediate potential for hydrogen bonding
Compound C - polar compound with high potential for hydrogen bonding

A)compound A, compound B, compound C
B)compound A, compound C, compound B
C)compound B, compound C, compound A
D)compound C, compound B, compound A

Question 20

The advantage of reporting column chromatography results in terms of capacity factor is that capacity factor does not vary with:

A)mobile phase flow rate
B)chromatography column dimensions
C)sample volume injected
D)any of the above