Chromatography

Which of the listed factors do not affect retention time in liquid chromatography?

• Flow rate of mobile phase

• Distribution of the sample component between the mobile and stationary phases

• Injection volume

• Mobile phase composition

In a gas chromatogram you observe that components with fast retention times have narrow but poorly resolved peaks, while the slowly eluting components have very broad peaks with long retention times. What would you do to solve this problem?

• Use a gradient of mobile phase gases

• Use temperature programming

• Use a longer column

• Use isothermal conditions

According to the Rate Theory of Chromatography, which of the following factors will not induce band broadening?

• Increasing the polarity of the mobile phase

• Resistance to mass transfer

• Longitudinal diffusion

• Eddy diffusion

You are asked to increase the resolution between two compounds in a reversed phase liquid chromatography separation. Which of the following actions would you take?

• Increase the polarity of the mobile phase solvent.

• Change the column to one with a larger stationary phase particle size.

• Increase the mobile phase flow rate.

• Use a shorter column.

Which of the following factors contributing to band broadening is not influenced by mobile phase flow rate?

• Longitudinal diffusion

• Resistance to mass transfer in the mobile phase

• Resistance to mass transfer in the stationary phase

• Eddy diffusion

Which two parameters are needed to calculate plate number, N?

• Column length and peak width

• Retention time and peak width

• Plate height and peak width

• Column length and retention time