Principles of Instrumental Analysis
Principles of Instrumental Analysis
7th Edition
ISBN: 9781305577213
Author: Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher: Cengage Learning
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Chapter 26, Problem 26.16QAP
Interpretation Introduction

(a)

Interpretation:

The resolution for species B and C from the given data should be determined.

Concept introduction:

The resolution of the column is defined as the separation of two species of the column.

Expert Solution
Check Mark

Answer to Problem 26.16QAP

The resolution is 2.01.

Explanation of Solution

Given:

Principles of Instrumental Analysis, Chapter 26, Problem 26.16QAP

The expression of resolution of the column is:

RS=2[(tR)C(tR)B]WC+WB ....... (I)

Here, the retention time of species C is (tR)C, the retention time of species B is (tR)B, the width time of the peak base of the species C is WC and the width time of the peak base of the species B is WB.

Substitute 15.7min for (tR)B, 13.3min for (tR)C, 1.07min for WC and 1.32min for WD in Equation (I).

RS=2[(15.7min)(13.3min)](1.07min)+(1.32min)=2(2.4min)(2.39min)=2.01

Thus, the resolution is 2.01.

Interpretation Introduction

(b)

Interpretation:

The selectivity factor for species B and C from the given data should be determined.

Concept introduction:

The resolution of the column is defined as the separation of two species of the column.

Expert Solution
Check Mark

Answer to Problem 26.16QAP

The selectivity factor is 1.24.

Explanation of Solution

The expression of selectivity factor is:

aC,B=(tR)CtM(tR)BtM ........ (II)

Here, the non-retained retention time is tM.

Substitute 15.7min for (tR)C, 13.3min for (tR)B and 3.1min for tM in Equation (II).

aC,B=(15.7min)(3.1min)(13.3min)(3.1min)=12.6min10.2min=1.24

Thus, the selectivity factor is 1.24.

Interpretation Introduction

(c)

Interpretation:

The length of column necessary to separate B and C species with a resolution of 2.5 should be determined.

Concept introduction:

The resolution of the column is defined as the separation of two species of the column.

Expert Solution
Check Mark

Answer to Problem 26.16QAP

The length of column necessary to separate the two species with a resolution of 2.5 is 37.98cm.

Explanation of Solution

The expression of length of the column is:

L=N2H ....... (III)

Here, the number of plates needed to separate the two species is N and the height of the plate is H.

The expression of relation of the resolution and number of plates is:

(RS)(RS)2=N1N2N2=(RS)2N1(RS)N2={(RS)2N1(RS)}2N2=N1(RS)22(RS)2

Here, the number of plates needed is N1 and the given resolution is (RS)2.

Substitute N1(RS)22(RS)2 for N2 in Equation (III).

L={N1(RS)22(RS)2}H ......... (IV)

Substitute 2.01 for (RS), 2.5 for (RS)2, 2455 for N1 and 0.01cm for H in Equation (IV).

L={(2455)(2.5)2(2.01)2}(0.01cm)=(3797.86)(0.01cm)=37.98cm

Thus, the length of column necessary to separate the two species with a resolution of 2.5 is 37.98cm.

Interpretation Introduction

(d)

Interpretation:

The time required to separate B and C species on the column of part c should be determined.

Concept introduction:

The resolution of the column is defined as the separation of two species of the column.

Expert Solution
Check Mark

Answer to Problem 26.16QAP

The time required to separate the two species on the column of part c is 24.29min.

Explanation of Solution

The expression of the relation of time required to separate the two species on the column is:

(tR)C(tR)=(Rs)2(RS)12 ........ (V)

Here, the given resolution is (RS)1 and time required to separate the two species on the column is tR.

Substitute 15.7min for (tR)C, 2.01 for RS and 2.5 for (RS)1 in Equation (V).

(15.7min)(tR)=(2.01)2(2.5)2tR=(15.7min)(2.5)2(2.01)2tR=24.29min

Thus, the time required to separate the two species on the column of part c is 24.29min.

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Substances A, B, C and D were found to have retention times of 8.3 min (A), 10.6 min (B), 12.4 min (C) and 13.5 min (D), respectively on an 15.0 cm long column. There was also an unretained species which appeared at 1.5 min. The widths of the peak bases were 0.90 min (A), 1.1 min (B), 1.3 min (C) and 0.80 min (D). Given this information listed above, please choose the most appropriate answer for the six questions listed below for the list of possible answers. Part A Calculate the capacity factor (k') for peak B and peak D. Part B. Calculate the resolution (R) between peaks B and D. Part C. What do the capacity factor and resolution tell you about the separation of peaks B and D on this column? Part D What are the theoretical plate number (N) for peaks Band D? Part E. What is the average plate height (H), based on the information in Part D and the column length listed above? Part F What would be the required length of a column to achieve a Rs of 2.07
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