Mixed 2 Flashcards
Which of the following statements about the charged groups in IEX stationary phases is correct?
A) They are involved in the exchange process and determine the specificity and strength of analyte binding.
B) They determine whether the stationary phase is an anion exchanger or a cation exchanger.
C) Cation exchangers have positively charged functional groups and possess exchangeable anions.
D) All of the above.
D) All of the above.
True or False: The matrix in IEX stationary phases determines the physical and chemical stability, flow characteristics, and may be responsible for unspecific binding effects.
True
Identify the material that was originally used as a matrix for ion exchange chromatography.
A) Cellulose
B) Dextran
C) Agarose
D) Polystyrene-divinylbenzene copolymers
D) Polystyrene-divinylbenzene copolymers
Which of the following statements about the porosity of the matrix in IEX stationary phases is incorrect?
A) Non-porous matrices are preferable for high-resolution separations to avoid diffusion effects.
B) Micropores increase the binding capacity but cause band broadening.
C) Macroporous particles with pore diameters of about 600-800 nm overcome the disadvantages of micropores.
D) High porosity offers a large surface area covered by charged groups, which is an advantage when separating small molecules.
D) High porosity offers a large surface area covered by charged groups, which is an advantage when separating small molecules.
What is the advantage of continuous bed matrices in IEX stationary phases?
A) They offer higher binding capacity compared to bead-based matrices.
B) They provide more homogeneous mobile phase flow and shorter diffusion distances for the analytes.
C) They are more physically and chemically stable than bead-based matrices.
D) They are less expensive to manufacture compared to bead-based matrices.
B) They provide more homogeneous mobile phase flow and shorter diffusion distances for the analytes.
Which of the following factors does NOT directly affect the chromatographic resolution in IEX?
A) Porosity of the matrix
B) Size and size distribution of the particles
C) Pore size of the matrix
D) Type of mobile phase used
D) Type of mobile phase used
True or False: The physical and chemical stability of the matrix in IEX is important for facilitating high flow rates during cleaning or re-equilibration steps.
True
Which of the following statements about mobile phases in IEX is incorrect?
A) Sodium chloride is a widely used eluent for protein separation because it has no significant effect on protein structure.
B) The competing ion in the mobile phase has the function of eluting sample components through the column.
C) The higher the concentration of the competing ion, the more effective the displacement of analyte ions from the stationary phase.
D) The nature of the competing ion does not affect the elution of solute ions.
D) The nature of the competing ion does not affect the elution of solute ions.
Identify the correct order of preference for exchanging ions at low concentrations and ordinary temperatures.
A) Higher valency > Higher atomic number
B) Higher atomic number > Higher valency
C) Higher valency = Higher atomic number
D) None of the above
A) Higher valency > Higher atomic number
Which of the following statements about the effect of flow rate and temperature in IEX is correct?
A) Higher flow rates cause lower elution volumes, while higher temperatures decrease chromatographic efficiency.
B) Higher flow rates cause higher elution volumes, while higher temperatures increase chromatographic efficiency.
C) Higher flow rates cause lower elution volumes, while higher temperatures increase chromatographic efficiency.
D) Higher flow rates and higher temperatures both cause higher elution volumes.
C) Higher flow rates cause lower elution volumes, while higher temperatures increase chromatographic efficiency.
Which of the following additives can be used in IEX mobile phases for solubilization of proteins?
A) Urea and guanidine hydrochloride
B) Detergents
C) Both A and B
D) None of the above
C) Both A and B
Which of the following is NOT a desired property of buffers used in IEX mobile phases?
A) High buffering capacity at the working pH
B) High solubility
C) High purity
D) High conductivity
D) High conductivity
Possibility of precipitation can occur when ______ buffer and ______ metal ions are mixed in IEX mobile phases.
A) phosphate, divalent
B) acetate, monovalent
C) citrate, trivalent
D) borate, divalent
A) phosphate, divalent
Which type of detector is the detector of choice for the majority of IEX applications?
A) UV-Visible absorbance detector
B) Refractive index detector
C) Electrical conductivity detector
D) Fluorescence detector
C) Electrical conductivity detector
True or False: The output signal from an electrical conductivity detector is inherently linearly related to the ion concentration in the detector cell.
False. The ‘out of balance signal’ is not inherently linearly related to the ion concentration in the cell. Thus, the electronic circuit modifies the response of the detector to provide an output that is linearly related to the ion concentration.
Which detection technique in IEX is suitable for analytes that exhibit a significant absorbance profile in the UV-Vis spectrum?
A) Amperometric detection
B) Photometric detection
C) Mass spectrometry
D) Electrical conductivity detection
B) Photometric detection
Identify the type of ionization technique used in mass spectrometry detection for IEX, which is suitable when the solute ions are anionic.
A) Positive-mode electrospray ionization (ESI)
B) Negative-mode electrospray ionization (ESI)
C) Atmospheric pressure chemical ionization
D) Electron impact ionization
B) Negative-mode electrospray ionization (ESI)
In the chromatograms shown in Figure 10, which type of IEX is used for the separation of inorganic anions (a) and inorganic cations (b)?
A) Anion exchange chromatography (a), Cation exchange chromatography (b)
B) Cation exchange chromatography (a), Anion exchange chromatography (b)
C) Both are anion exchange chromatography
D) Both are cation exchange chromatography
A) Anion exchange chromatography (a), Cation exchange chromatography (b)
In IEX, ______ have no or only weak UV chromophores, making ______ the detector of choice for most applications.
A) anions, conductivity
B) cations, conductivity
C) both anions and cations, conductivity
D) both anions and cations, UV-Vis absorbance
C) both anions and cations, conductivity
True or False: The mobile phase in IEX typically consists of an aqueous solution of a suitable salt or mixtures of salts, with the addition of a small percentage of an organic solvent.
True
What does HILIC stand for?
Hydrophilic Interaction Chromatography
HILIC can be described as a variation of ___________ performed using a polar stationary phase.
Reversed Phase Liquid Chromatography (RPLC)
In HILIC, the mobile phase typically contains _____ of aqueous solvent/buffer.
a) >60%
b) <60%
c) Exactly 60%
d) None of the above
b) <60%
What are the three mechanisms of retention in HILIC?
1) Hydrophilic partitioning,
2) Hydrogen bonding,
3) Electrostatic interactions
In the chromatogram shown in Figure 4, which peak corresponds to epinephrine in HILIC?
a) Peak 1
b) Peak 2
c) Both peaks 1 and 2
d) Neither peak 1 nor 2
a) Peak 1
Name the different types of stationary phases available for HILIC separation.
Silica, Amino, Cyano, Diol, Zwitterionic, Polymer-based
True or False: An increase in the percentage of organic solvent in the mobile phase leads to a decrease in retention in HILIC.
False
Which of the following organic solvents has the strongest elution strength in HILIC?
a) Acetonitrile
b) Methanol
c) Isopropanol
d) Tetrahydrofuran
d) Tetrahydrofuran
The recommended buffers for HILIC are ___________ of acetic and formic acids.
ammonium salts
In Figure 8, the retention of salicylic acid (negatively charged) on Hypersil GOLD HILIC (positively charged) decreases as the buffer concentration _____.
a) increases
b) decreases
c) remains constant
d) None of the above
a) increases
True or False: Increased salt concentrations result in decreased retention of positively charged solutes on stationary phases with the same charge.
True
Which of the following statements is NOT a recommendation for mobile phase selection in HILIC applications?
a) Use acetonitrile or other polar, water-miscible organic modifiers.
b) Have a high organic content, between 60 to 97%.
c) Use buffer salts such as ammonium acetate and ammonium formate.
d) Run gradients from 100% organic to 100% aqueous.
d) Run gradients from 100% organic to 100% aqueous.
In HILIC, the resulting elution order of solutes is _____ that observed in a reversed phase separation.
a) the same as
b) roughly the opposite of
c) unrelated to
d) none of the above
b) roughly the opposite of
What is the mechanism behind the formation of an aqueous layer on the surface of the polar stationary phase in HILIC?
Polar analytes preferentially partition into this aqueous-rich layer.
In HILIC, a minimum of _____ water is necessary to ensure sufficient hydration of the stationary phase.
3%
True or False: As the buffer pH increases, the retention of acetylsalicylic acid (pKa = 3.5) in HILIC also increases.
True
In Figure 10.2, the retention of cytosine and cytidine on Hypersil GOLD HILIC increases with increasing ammonium acetate concentration due to _____.
a) increased electrostatic interactions
b) increased hydrophobic interactions
c) enhanced hydrogen-bonding interactions
d) none of the above
c) enhanced hydrogen-bonding interactions
Which of the following statements is correct regarding the effect of buffer pH in HILIC?
a) Charged compounds are less hydrophilic and therefore less retained.
b) Charged compounds are more hydrophilic and therefore more retained.
c) Buffer pH has no effect on the retention of charged compounds.
d) The effect of buffer pH depends on the type of stationary phase used.
b) Charged compounds are more hydrophilic and therefore more retained.