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
Question
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Chapter 32, Problem 32.8QAP
Interpretation Introduction

(a)

Interpretation:

The counting rate 9cpm is the background counting rate in the laboratory which was measured at the time period of 3 min and it is required that the value of standard relative deviation should be less than the 5% (σRc/Rc<0.05). The total number of count is to be determined when the counting rate is 50cpm.

Concept introduction:

The formula for the standard deviation for the corrected counting rate is given as-

σRc=Rxtx+Rbtb ……. (1)

Where,

Rx = counting rate for sample

Rb = counting rate for background

tx = time required for counting rate for sample

tb = time required for counting rate for background

σRc = standard deviation for the corrected counting rate

Relative standard deviation is represented by the following formula-

=σRcRc …… (2)

Also,

Rc=RxRb

Interpretation Introduction

(b)

Interpretation:

The counting rate 9cpm is the background counting rate in the laboratory which was measured at the time period of 3 min and it is required that the value of standard relative deviation should be less than the 5% (σRc/Rc<0.05). The total number of count is to be determined when the counting rate is 300cpm.

Concept introduction:

The formula for the standard deviation for the corrected counting rate is given as-

σRc=Rxtx+Rbtb ……. (1)

Where,

Rx = counting rate for sample

Rb = counting rate for background

tx = time required for counting rate for sample

tb = time required for counting rate for background

σRc = standard deviation for the corrected counting rate

Relative standard deviation is represented by the following formula-

=σRcRc …… (2)

Also,

Rc=RxRb

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