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Chapter 24: Q26P (page 664)

(a) How can you improve the resolution between two closely spaced peaks in gas chromatography?

(b) What approach from (a) would be most cost effective (not involve a purchase)?

Short Answer

Expert verified

(a). In gas chromatography, to show how to improve the resolution between two closely spaced peaks.

(b). Optimizing the flow rate and temperature in gas chromatography is the most effective way to improve the resolution between the two closely spaced peaks.

Step by step solution

01

Definition of chromatography 

As a result of differential distribution of the solutes as they flow over or over a stationary liquid or solid phase, a chemical mixture transported by a liquid or gas is split into components.

02

Determine the resolution between two closely spaced peaks in gas chromatography  

(a)

  • It is necessary to discuss how to improve the resolution between two closely spaced peaks in gas chromatography.
  • In gas chromatography, to show how to improve the resolution between two closely spaced peaks.
  • In gas chromatography, there are several approaches to increase the resolution between two closely spaced peaks:
  • Increase the column's length while decreasing its diameter.
  • By altering the stationary phase of the system.
  • By maximising the pace of flow.
  • Increase the retention factor by increasing the thickness of the film as the temperature drops.
03

Determine in what approach from (a) would be most cost effective (not involve a purchase)

(b)

  • It is necessary to take the most cost-effective technique.
  • To provide the most cost-effective solution
  • Optimizing the flow rate and temperature in gas chromatography is the most effective way to improve the resolution between the two closely spaced peaks.

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Most popular questions from this chapter

Genotoxic compounds damage DNA and cause mutations or cancer.Regulatory guidelines limit genotoxic impurities in pharmaceuticals. Mesityl oxide (4-methyl- 3-penten-2-one) is an intermediate product in the synthesis of some drugs. Search the literature for a gas chromatography method for the determination of mesityl oxide in the pharmaceutical enalapril maleate and answer the following questions.

(a) Give the citation (authors, title, journal name, year, volume, pages) for a research paper describing this analysis.

(b) What is the instrumental method used?

(c) What type of column was used?

(d) What quantification method is used?

(e) What are the precision, limit of detection, limit of quantification, and linear range of the method?

(f) For how long could a standard solution be used?

What is the purpose of derivatization in chromatography? Give an example.

(a) What are the advantages and disadvantages of temperature programming in gas chromatography?

(b) What is the advantage of pressure programming?

The antitumor drug gimatecan is available as nearly pure (S)-enantiomer. Neither pure (R)-enantiomer nor a racemic (equal) mixture of the two enantiomers is available. To measure small quantities of (R)-enantiomer in nearly pure (S)-gimatecan, a preparation was subjected to normal-phase chromatography on each of the enantiomers of a commercial, chiral stationary phase designated (S,S)- and (R,R)-DACH-DNB. Chromatography on the (R,R)-stationary phase gave a slightly asymmetric peak at tr 5 6.10 min with retention factor k 5 1.22. Chromatography on the (S,S)- stationary phase gave a slightly asymmetric peak at tr 5 6.96 min with k 5 1.50. With the (S,S) stationary phase, a small peak with 0.03% of the area of the main peak was observed at 6.10 min.

Chromatography of gimatecan on each enantiomer of a chiral stationary phase. Lower traces have enlarged vertical scale. [Data from E. Badaloni, W. Cabri, A. Ciogli, R. Deias, F. Gasparrini, F. Giorgi, A. Vigevani, and C. Villani, “Combination of HPLC ‘Inverted Chirality Columns Approach’ and MS/MS Detection for Extreme Enantiomeric Excess Determination Even in Absence of Reference Samples.” Anal. Chem. 2007, 79, 6013.]

(a) Explain the appearance of the upper chromatograms. Dashed lines are position markers, not part of the chromatogram. What Problems 709 would the chromatogram of pure (R)-gimatecan look like on the same two stationary phases?

(b) Explain the appearance of the two lower chromatograms and why it can be concluded that the gimatecan contained 0.03% of the (R)-enantiomer. Why is the (R)-enantiomer not observed with the (R,R)-stationary phase?

(c) Find the relative retention (a) for the two enantiomers on the (S,S)-stationary phase.

(d) The column provides N 5 6 800 plates. What would be the resolution between the two equal peaks in a racemic (equal) mixture of (R)- and (S)-gimatecan? If the peaks were symmetric, does this resolution provide baseline separation in which signal returns to baseline before the next peak begins?

Describe how retention time of butanol on a poly (ethylene glycol) column will change with increasing temperature. Use the retention time for butanol in Figure 24-9b as the starting point.
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