1 ) Which of the following statements is incorrect?:
The capacity factor of an analyte is usually considered to be:
- (Vr – V0)/V0 where Vr is the retention volume of the analyte and V0 the column void volume.
- (tr-t0)/t0, where tr is the retention time for the analyte and t0 the retention time for an unretained component.
- Proportional to the molecular weight of the analyte.
- Proportional to the column phase ratio.
2) Which of the following statements is correct about the capacity factor?:
- it is considered to be a thermodynamic parameter.
- It is a measure of the mass transfer efficiency of the column.
- It decreases strongly with increased flow rate.
- It is strongly dependent of the amount analyte injected.
3) Which of the follwing statements is incorrect?:
The capacity factor for an analyte is:
- Proportional to the adsorption constant to the stationary phase for the analyte.
- Dependent of its adsorption isotherm to the stationary phase.
- Increasing with decreasing column porosity, for a given stationary phase material.
- Proportional to the column length.
4 ) Which of the following statements is correct?
- Under normal chromatographic conditions peak broadening is mainly due to diffusion.
- In elution chromatography the analyte is diluted when it migrates through the column.
- The peak width is independent of the mobile phase velocity.
- The peak width is a thermodynamic quantity.
5 ) Which of the following statements is incorrect?
- The plate height is proportional to the column length.
- The van Deemter equation is used to estimate the plate height.
- The Knox equation is used to estimate the reduced plate height.
- The plate height is a measure of the peak width.
6 ) Which of the following statements is correct?
- An unbuffered mobile phase is recommended to separate protolytic analytes on an RP-column.
- Reversed phase chromatography is generally the most appropriate chromatographic technique to separate noble metal ions.
- Interactions with silanol groups are important when aromatic analytes are separated on an RP-column.
- Retention of an analyte in reversed phase chromatography is related to its hydrophobicity.
7 ) You want to analyse benzene, toluene and p-xylene isocratically by RP-chromatography but don’t get a baseline separation between the analytes with the acetonitrile/water mobile phase that you are using. What will you do?
- Decrease the acetonitrile content of your mobile phase.
- Change the detector wavelength to a shorter wavelength.
- Change to a shorter column.
- Abandon the requirement of using isocratic analysis and use a gradient instead.
8 ) Which of the follwing statements is incorrect?
- In ion exchange chromatography of ions, retention varies with the concentration of salt in the mobile phase.
- It is, generally speaking, easy to separate a mono-charged ion from a di-charged ion by ion exchange chromatography.
- The stationary phase of a strong cat-ion exchanger consists of carboxylic groups.
- Ion exchange chromatography is a common technique to separate proteins.
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