/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q38P (a) When you try separating an u... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 25: Q38P (page 711)

(a) When you try separating an unknown mixture byreversed-phase chromatography with 48%acetonitrile 50%water,the peaks are too close together and are eluted in the range k = 2- 6Should you use a higher or lower concentration of acetonitrile in thenext run?

(b) When you try separating an unknown mixture by normal-phasechromatography with 50%hexane50% methyl t-butyl ether, thepeaks are too close together and are eluted in the range k = 2 - 6Should you use a higher or lower concentration of hexane in thenext run?

Short Answer

Expert verified

(a) Lower concentration of acetonitrile should be used because lower solvent strength increases the difference in retention between compounds.

(b) Solvent that would lower the solvent strength is recommended for the use. In this case it is hexane.

Step by step solution

01

Define Acetonitrile:

Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula CH3CN. This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not classed as organic). It is produced mainly as abyproduct of acrylonitrile manufacture.

02

Concentration of Acetonitrile:

We should use lower concentration of acetonitrile because lower solvent strength increases the difference in retention between compounds.

01

DefineChromatography

Chromatography is a group of laboratory techniques used to separate the components of a mixture by passing the mixture through a stationary phase.

02

The Concentration of Hexane:

We should use a higher concentration of hexane in the next run because in normal-phase chromatography, solvent strength increases as the solvent becomes more polar (in this case methyl t-butyl ether is more polar). So, to improve resolution and increase the retention time,such solvent should be used that would lower the solvent strength. In this case it is hexane.

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.

Over 30 million students worldwide already upgrade their learning with 91影视!

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

Use Figure 25-30 for the following questions:

(a) What pH would be best for the separation of benzoic acid, 4-nitrophenol, and 3-methylbenzoic acid?

(b) What pH would be best for the separation of benzoic acid, 3-methylbenzoic acid, and 4-methylaniline?

(c) What pH would be best for separation of 4-nitrophenol, 4-methylaniline, and codeine on a typical C18-silica column?

If along 15cmHPCL column has a place height of 5.0 what will be the half-width (in seconds) of a peak eluted at 10.0min? if plate height5渭尘,what will bew1/2?

Question: what are the general steps in developing an isocratic separation for reversed-phase chromatography?

  1. Use equation 25-1to estimate the length of a column required to achieve1.0脳104plates if the stationary phase particles size is10.5,5.0,3.0,or1.5渭尘

  2. If the retention time was 20mins on the 10.0渭尘 particle size column, what is the retention time on the 5.0,3.0,or1.5渭尘columns from part (a)? Assume that flow rate is constant for all columns.

  3. Use equation25-2to estimate the pressure of the column in (a) given that the pressure of the10.0渭尘column was4.4Mpa

  4. If the flow rate was2.0mL/min , what is the baseline width for the peaks on 10.5,5.0,3.0,or1.5渭尘columns form part (a)?

  5. Which of these column configurations would require a UHPLC instrument?

(a) Why does mobile phase strength increase as solvent

becomes less polar in reversed-phase chromatography, whereas

mobile phase strength increases as solvent becomes more polar in

normal-phase chromatography?

(b) What kind of gradient is used in supercritical fluid chromatography?
See all solutions

Recommended explanations on Chemistry Textbooks

Inorganic Chemistry

Read Explanation

Nuclear Chemistry

Read Explanation

The Earths Atmosphere

Read Explanation

Organic Chemistry

Read Explanation

Chemical Reactions

Read Explanation

Making Measurements

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.