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Test: HPLC method developer


Test: Novice
Test: HPLC user
Test: HPLC method developer
Test: HPLC scientist

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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