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Chapter 26: Q47P (page 750)

When the following three compounds are separated by micellar electrokinetic chromatography at, three peaks are observed. When 10mMvα-cyclodextrinis added to the run buffer, two of the three peaks split into two peaks, giving a total of five peaks. Explain this observation and predict which compound does not split.

Short Answer

Expert verified

Cyclobarbital and Thiopental will generate two peaks whereas phenobarbital would have one peak.

Step by step solution

01

Definition of electrokinetic chromatography

Micellar electrokinetic chromatography (MEKC) is a chromatography technique used in analytical chemistry. It used for separating neutral molecules and ions.

02

Explanation of observation

Among the three compounds, cyclobarbital and thiopental have one chiral carbon, whereas phenobarbital is achiral. Both cyclobarbital and thiopental form non-superimposable mirror images known as enantiomers.

The enantiomers will spend different time interacting with cyclodextrin as they migrate through the capillary. This will lead to splitting of the peaks cyclobarbital and thiopental into two separate peaks resulting in a total of five peaks. The chiral centres for cyclobarbital and thiopental are marked with an asterisk.

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Most popular questions from this chapter

Would molecular exclusion, affinity, or hydrophobic interaction chromatography be most appropriate for each of the following applications?

  1. Purifying and concentrating a crude mixture of an antibody.
  2. Desalting a solution containing a 30kDa protein.
  3. Finding the molecular mass distribution of polystyrene with 15kDa average mass.
  4. Separation of cytochrome c (12 400 Da) and ribonuclease A (12 600 Da). Cytochrome c has lower surface hydrophobicity than ribonuclease A.

(a) How can molecular exclusion chromatography be used to measure the molecular mass of a protein?

(b) Which pore size in Figure 26-15 is most suitable for chromatography of molecules with molecular mass near 100 00?

(a) Suppose that the reservoir in Figure 26-7 contains 1.5 L of 2.0 M K2PO4. For how many hours can the reservoir provide 20mM KOH at a flow rate of 1.0 mL/min if 75% consumption ofin the reservoir is feasible?

(b) What starting and ending current would be required to produce a gradient from 5.0 mM KOH to 0.10 M KOH at 1.0 mL/min flow rate?

(a) The suppressor in Figure 26-9 enables low parts-per-billion conductivity detection for anions such asCl-andBr-,.but very poor detection limits for anions such asCN-and borate. Explain why.

(b) Mixtures of sodium carbonate and bicarbonate can be used as eluent in suppressed-ion anion chromatography. Detection limits are poorer than with hydroxide eluent due to higher background conductivity. Explain why

State three different methods to reduce electroosmotic flow. Why does the direction of electroosmotic flow change when a silica capillary is washed with a cationic surfactant?
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