b) In the separation of a sample containing five polar compounds, chromatogram A was obtained using an isocratic mixture of hexane:acetone with a ratio of 75:25. The separation was improved (chromatogram B) using a gradient elution approach with the same mobile phase mixture. Suggest the gradient elution program used in obtaining chromatogram B. Explain your answer. mAU 2 40 3 5 30 20 10 -10 1 2 3 4 6 min Chromatogram A mAU 40 3 30 5 20 10 -10 2 4. 6 min Chromatogram B

b) In the separation of a sample containing five polar compounds, chromatogram A was obtained using an isocratic mixture of hexane:acetone with a ratio of 75:25. The separation was improved (chromatogram B) using a gradient elution approach with the same mobile phase mixture. Suggest the gradient elution program used in obtaining chromatogram B. Explain your answer. mAU 2 40 3 5 30 20 10 -10 1 2 3 4 6 min Chromatogram A mAU 40 3 30 5 20 10 -10 2 4. 6 min Chromatogram B

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter26: An Introduction To Chromatographic Separations

Section: Chapter Questions

Problem 26.22QAP

See similar textbooks

Similar questions

separate a mixture containing acetone, acetamide and 1,2-dichloroethane using a high- performance liquid chromatography (HPLC) technique. The instrument was equipped with a 40-cm column packed with cyano propyl bonded to the siloxane backbone material. i) List THREE (3) examples of mobile phase solvent/solvent systems that can be used with the column above. ii) Determine the sequence in which the three analytes eluted from the column and explain the underlying principle applied. iii) Sketch the chromatogram that would be produced if the column was replaced with a column filled with C18 hydrocarbon bound to the siloxane backbone material and acetonitrile was employed as the mobile phase. Label the peaks observed.
Arrange in INCREASING Rf if the mixture underwent paper chromatography with the same solvent system. Explain how you get the answer I. 2-chloropentaneII. pentanoic acidIII. cyclopentaneIV. pentanal a. II = IV < III < I b.II < IV < I < III c.I < II < III < IV d.III < I < IV < II
Which liquid chromatography mode uses an isocratic separation? a. Size-exclusion chromatography b. Adsorption chromatography c. Partition chromatography d. Ion chromatography e. Affinity chromatography
In ion-exclusion chromatography, ions are separated from nonelectrolytes (uncharged molecules) by an ion-exchange column. Nonelectrolytes penetrate the stationary phase, whereas ions with charge of the same sign as that of the stationary phase are repelled by the stationary phase. Because electrolytes have access to less of the column volume, they are eluted before nonelectrolytes. A mixture of trichloroacetic acid (TCA, pKa 5 20.5), dichloroacetic acid (DCA, pKa 5 1.1), and monochloroacetic acid (MCA, pKa 5 2.86) was separated by passage through a cation-exchange resin eluted with 0.01 M HCl. The order of elution was TCA , DCA , MCA. Explain why the three acids are separated and the order of elution.
As a newly appointed research officer, Marissa has been assigned a task to separate a mixture containing acetone, acetamide and 1,2-dichloroethane using a high-performance liquid chromatography (HPLC) technique. The instrument was equipped with a 40-cm column packed with cyano propyl bonded to the siloxane backbone material. i) List THREE (3) examples of mobile phase solvent/solvent systems that can be used with the column above. ii) Determine the sequence in which the three analytes eluted from the column and explain the underlying principle applied. iii) Sketch the chromatogram that would be produced if the column was replaced with a column filled with C18 hydrocarbon bound to the siloxane backbone material and acetonitrile was employed as the mobile phase. Label the peaks observed.
in HPLC, what does it mean to equilibrate the system. Let us assume that the system is currently running 100%B. You have told them to run the first standard of caffeine using Reverse Phase chromatography with a C18 column, 30% A (Water/0.1%TFA) and 70% B (MeOH/0.1%TFA).What should I equilibrate the system to and for how long?
The following data give the recovery of bromide from spiked samples of vegetable matter, measuredusing a gas–liquid chromatographic method. The same amount of bromide was added to each specimen(Roughan, J.A., Roughan, P.A. and Wilkins, J.P.G., 1983, Analyst, 108: 742).Tomato: 777 790 759 790 770 758 764 ug/gCucumber: 782 773 778 765 789 797 782 ug/g(a) Test whether the recoveries from the two vegetables have variances which differ significantly.(b) Test whether the mean recovery rates differ significantly.
For thin layer chromatography, why should a piece of filter paper that is moistened with the developing solvent be placed inside the developing chamber before the plate is developed? Group of answer choices to absorb excess solvent from the TLC chromatogram plate to absorb any impurities in the eluent to signal completion of the experiment to ensure that the atmosphere of the chamber is saturated with eluent vapor
Next, 2.00 mL of 9.63 mM S was added to 10.00 mL of a solution of unknown concentration of X, and the mixture was diluted to 25.0mL. Chromatographic analysis of this solution produced peak areas of 4822 for X and 4099 for S. What was the concentration of 5 (in mM) of the 25.0mL solution?
hree components in a mixture have varying distribution constants between the mobile phase and the stationary phass One of the components has a very low distribution constant, Would this component likely elute first or last and how would you design an experiment or modify the components of the separation to make it perform in the opposite manner?
(h) Describe a chromatographic technique that could be suitable for studying the molecular weight distribution of poly(phenylenevinylene) derivatives that are soluble in organic solvents. Explain the physical basis on which separation could occur and suggest how the polymers could be detected after elution.
Briefly explain how analytes are separated using the following modes of chromatography. Adsorption chromatography Partition chromatography Molecular exclusion chromatography Affinity chromatography Ion-exchange chromatography