Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 25: Q8P (page 707)

a) UHPLC can provide exquisite resolution when run slowly on long columns or rapid separation with reasonaple resolution if short columns are run fast. the drug acetaminophern run on a 50×2.1mmc18UHPLC column has a retention time of 0.63min and a width at half-height of 2.3s.Find the plate number and plate height. How many1.7μm diameter particles places placed dide-by are equal to one theoretical plate?

b) From figure25-3,we expect an optimum plate height of 4μm how many particles placed side-by- side are equal to one theroretical plate? Do you think the column in (a) is being run for maximum resolution or maximum speed?

Short Answer

Expert verified

UHPLC can provide exquisite resolution when run slowly on long columns.

how many particles placed side-by- side are equal to one theoretical plate.

N=5.55.(37.8s)2(2.3)2N=1500

4μm1.7μm=2.4

(a)N=1500;H=33μm;19.4particle/plate

b) 2.4particle/plate

Step by step solution

01

definition of plate calculated using the formula

a) The number of plates on column can be calculated using the formula

N=5.552.trw21/2

N=5.55.(37.8s)2(2.3)2N=1500

The plate height is:

H=LNH=50mm1500H=0.033mm=33μm

The number of particles that are equal to one theoretical plate is

33μm1.7μm=19.4particle/plate

02

theoretical plate

The number of particles that are placed side-by-side and equal to one theoretical plate is:

4μm1.7μm=2.4particle/plate

The column in task (a) is being run for maximum speed because it has higher plate height and number of particles. b

Hence,

(a)N=1500;H=33μm;19.4particle/plate

b) 2.4particle/plate

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

(a) use figure 25-28a select a tetrahydrofurn/water mobile phase strength of equivalent strength to 80%methanol.

(b)Describe how to prepare 1 L of this tetrahydrofurn mobile phase.

(c)what limitation would be imposed by the use tetrahydrofurn.

Question: Explain how to use a gradient for the first run to decide whether isocratic or gradient elution would be more appropriate.

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?

Question: what are the general steps in developing an isocratic separation for reversed-phase chromatography?
  1. According to equation 25-2if all conditions are constant, but particle size is reduced from3μmto0.7μmby what factor must pressure be increased to maintain constant linear velocity?
  2. If all conditions except pressure are constant, by what factor will linear velocity increase if column pressure is increased by a factor of 10?
  3. With 0.7μmparticles in a 9cm×50column, increasing pressure from 70MPato700MPa decreased analysis time by approximately a factor of 10while increasing plate count from
  4. 12000to4500059Explain why small particles permit faster flow without losing efficiency or,in this case,with improved efficiency.
See all solutions

Recommended explanations on Chemistry Textbooks

The Earths Atmosphere

Read Explanation

Inorganic Chemistry

Read Explanation

Kinetics

Read Explanation

Physical Chemistry

Read Explanation

Making Measurements

Read Explanation

Chemical Analysis

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free