1 ) Why should not mobile phases with pH above 8 be used with silica based columns?

- The silica dissolves at high pH so that the column deteriorates.

- The mobile phase becomes flammable at high pH.

- The pressure becomes too high.

- The analytes degrade at high pH.

 

 

 

2) Which organic modifiers are most common in reversed phase chromatography.

- Isopropanol and toluene.

- Methylenechloride and chloroform.

- Methanol and acetonitrile.

- Ether and acetone.

 

 

 

3) Chromatographic retention is due to:

- Different injection times by the autosampler.

- Adsorption of the analyte to the stationary phase.

- Differences in absorbance in the UV detector.

- Deviations in the flow from the pump.

 

 

 

4) Generally, how do you make a calibration curve?

- By using a RI-detector and sucrose as analyte.

- Injecting a known amount of analyte and determine the peak area.

- Accurately measure the flow rate.

- Setting the detector response to zero.

 

 

 

5) What is characteristic of gradient chromatography?

- The detector scans over a wide range of wavelengths.

- The mobile phase is unbuffered.

- A gradient of flow velocity is created.

- A gradient of mobile phase composition is created.

 

 

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