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Unformatted text preview: A NAL R EVISION Q UESTIONS Chromatography 1) Which one of the following statements is wrong ? a) The eluent is the fluid entering the column b) The eluate is the fluid leaving the column c) Separation of a mixture is achieved through differential interaction of the substances in the mixture with the stationary phase. d) The mobile phase is the eluent and the stationary phase leaving the column is the eluate e) The stationary phase may be be a solid or liquid. 2) With regards to the HPLC-UV chromatogram shown for the separation of sugar and caffeine, which one of the following statements is wrong ? a) 5.0 and 9.2 min are the unadjusted retention times of substances A and B respectively b) 3.2 mL is the adjusted retention volume of substance A c) The adjusted retention time for substance B is 4.2 min d) The adjusted retention time for substance A is 4.0 min e) The adjusted retention volume for substance B is 6.56 mL 3) a) I = eddy diffusion, II = multiple paths b) I = longitudinal diffusion, II = multiple paths c) I = equilibrium time, II = eddy diffusion d) IV = eddy diffusion e) IV = I+III 4) Which one of the following statements regarding plate height is wrong ? a) Plate height due to multiple paths is reduced by using small diameter column packings b) Plate height due to multiple paths is reduced by using very uniform diameter column packings c) Longitudinal diffusion is reduced by increasing mobile phase flow rate d) Longitudinal diffusion is reduced when using solvents with low diffusion coefficient e) Plate height due to longitudinal time is reduced by increasing the thickness of the stationary phase 5) Which one of the following statements regarding plate height contribution is wrong ? a) There is no multiple paths plate height contribution in a GC capillary column b) The Van Deempter plot for GC is always higher than that for HPLC c) Heating the HPLC column increases the rate of mass transfer loading to lower plate height due to equilibration time d) Lowering the partical size of a column packing helps to lower the overall plate height e) Longitudinal difference is lower in GC compared to HPLC 6) Which of the following statements is wrong with regards to extra column broading: a) The term ‘extra column broadening’ arises because it does not appear as a term in the van Deempter equation. b) The total observed band broadening is the sum of the band broadening effects from the column, extra column and sample volume/matrix effects. c) The internal tubing diameter makes a significant contribution to extra column broadening d) Extra column broadening is independent of flow rate 7) Which one of the following statements is correct with regards to the chromatographers triangle?...
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- Spring '10
- Chromatography, following statements, mobile phase