Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 25: Q4P (page 707)

a. Why is high pressure needed in HPLC?

b. For a given column length , why do smaller particles give a higher plate number?

c. What is bonded phase in liquid chromatography?

Short Answer

Expert verified

The high pressure in HPLC is needed for usable flow rate.

Smaller particles have a higher plate number because the optimum flow rate for smaller particles is faster because the distance through which the solute must diffuse is shorter.

A bonded stationary phase is covalently attached to the surface.

Step by step solution

01

Step 1:Explanation

For the part (a), the high pressure in HPLC is needed for usable flow rate.

For the part (b), the Smaller particles have a higher plate number because the optimum flow rate is faster because the distance through which the solute must diffuse is shorter.

02

Explanation

For the part (c), a bonded stationary phase is covalently attached to the surface. For an example, silica.

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) Nonpolar aromatic compounds were separated by HPLC on an octadecyl(C18)bonded phase. The eluent was 65 vol% methanol in water. How would the retention times be affected if 90% methanol were used instead?

(b) Octanoic acid and 1-aminooctane were passed through the same column described in (a), using an eluent of 20% methanol/80% buffer (pH 3.0). State which compound is expected to be eluted first and why.

role="math" localid="1656416023291" CH3CH2CH2CH2CH2CH2CH2CO2HOctanoicacidCH3CH2CH2CH2CH2CH2CH2CH2NH21‐Aminooctane

(c) Polar solutes were separated by hydrophilic interaction chromatography (HILIC) with a strongly polar bonded phase. How would retention times be affected if eluent were changed from 80 vol% to 90 vol% acetonitrile in water?

(d) Polar solutes were separated by normal-phase chromatographyon bare silica using methyl t-butyl ether and 2-propanol solvent. How would retention times be affected if eluent were changed from 40 vol% to 60 vol% 2-propanol? (Hint: See Table 25-4.)

use figure 25-17to suggest which type of liquid chromatography you could use to separate compounds in each of the following categories.

(a)Molecular mass <2000,soluble in octane

(b) Molecular mass <2000 ,soluble in methanol-water mixtures

(c) Molecular mass <2000 ,weak acid

(d)Molecular mass<2000 ,soluble highly polar

(e) Molecular mass <2000 ,ionic

(f)Molecular mass<2000,soluble in water in nonionic various

(g) Molecular mass<2000,soluble in water in water, variety of changes

(h) Molecular mass<2000,soluble in tetrahydrofuran

Question: Literature search problem: Human serum albumin (HSA) is an important protein ingredient in cryopreservation media used in procedures such as in vitro fertilization. Search the literature for a high-performance liquid chromatography method for the determination of human serum albumin and the stabilizer N-acetyl tryptophan in medical devices.

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

(b) What alternative methods could be used for analysis of human serum albumin?

(c) What type of analytical column is used for the separation?

(d) How long was the gradient? How long were the additional wash and equilibration steps within the gradient method?

(e) What parameters were assessed in the method validation?

(f) Why were particles with 300 Å pores used?

What are the general steps in developing as isocratic separation for reversed-phase chromatography with one organic solvent and temperature as variable?

(a) Make a graph showing retention times of peaks 6, 7, and 8 in Figure 25-12 as a function of %acetonitrile (%B). Predict the retention time of peak 8 at 45% B.

(b) Linear-solvent-strength model: In Figure 25-12, tm = 2.7 min. Compute k for peaks 6, 7, and 8 as a function of %B. Make a graph of log k versus Φ, where Φ= %B/100. Find the equation of a straight line through a suitable linear range for peak 8. The slope is -S and the intercept is log kw. From the line, predict tr for peak 8 at 45% B and compare your answer with (a).

(c) Gradient elution: A linear eluent gradient from 40 to 80% acetonitrile over 30 min is performed on the column in Figure 25-12. Assuming a dwell volume of 0 mL, use your data from (b) to plot the retention factor of peaks 6 and 8 during the gradient. What are the general characteristics of the plot?

(d) Why are the peaks in a gradient separation sharp?
See all solutions

Recommended explanations on Chemistry Textbooks

Kinetics

Read Explanation

The Earths Atmosphere

Read Explanation

Making Measurements

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Nuclear Chemistry

Read Explanation

Inorganic Chemistry

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