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Chapter 26: Q12P (page 747)

(a) State the purpose of the separator and suppressor in suppressed ion chromatography. For cation chromatography, why is the suppressor an anion-exchange membrane?

Short Answer

Expert verified

The solution to the above questions are:

  1. The suppressed ion chromatography os suitable for anion analysis.
  2. For cation chromatography, the suppressor replaces anions from eluent.

Step by step solution

01

Explanation of suppressed ion chromatography being the suitable for anion analysis:

  • The suppressor causes the reduction in the conductivity of the eluent by an exchange in the sample counter ions and eluent with ions derived by a suppressor.
  • It changes cations to hydrogen ions with higher conductivity→H2O
  • It neutralizes the eluent
  • Ions are separated with ion exchange process via separator column.
02

Step2:For cation Chromatography:

In this case the suppressor is an anion – exchange membrane because the suppressor replaces anions from eluent with hydroxyl ions via anion-exchange membrane

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Most popular questions from this chapter

(a) Explain how anions and cations can be separated by hydrophilic interaction chromatography in Figure 25-4, using the zwitterion stationary phase in Figure 25-16. Why does the gradient go from CH3CN.CH3CNto lowcontent?

(b) Explain how the charged aerosol detector used in Figure 26-4 works.

What is the effect on injection time if you decrease the applied voltage by a factor of 2?

Figure 26-24 shows the effect on resolution of increasing voltage from 28 to120kV

(a) What is the expected ratio of migration times(t120kV/t28kV)in the two experiments? Measure the migration times for peak 1 and find the observed ratio.

(b) What is the expected ratio of plates (N120kv/N28kv)in the two experiments?

(c) What is the expected ratio of bandwidths(σ120kv/σ28kv)?

(d) What is the physical reason why increasing voltage decreases bandwidth and increases resolution?

Consider a negatively charged protein adsorbed on an anion-exchange gel at pH 8.

(a) How will a gradient of eluent pH (from pH 8to some lower pH) be useful for eluting the protein? Assume that the ionic strength of the eluent is kept constant.

(b) How would a gradient of ionic strength (at constant pH) be useful for eluting the protein?

(a) A long thin molecule has a greater friction coefficient than a short fat molecule. Predict whether fumarate or maleate will have greater electrophoretic mobility.

(b) Electrophoresis is run with the injection end positive and the detection end negative. At pH 8.5, both anions have a charge of 22.The electroosmotic fl ow from the positive terminal to the negative terminal is greater than the electrophoretic flow, so these two anions have a net migration from the positive to the negative end of the capillary in electrophoresis. From your answer to part (a), predict the order of elution of these two species. (c)At pH 4.0, both anions have a charge close to 21, and the electroosmotic fl ow is weak. Therefore electrophoresis is run with the injection end negative and the detection end positive. The anions migrate from the negative end of the capillary to the positive end.Predict the order of elution.
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