Exploring Chemical Analysis
Exploring Chemical Analysis
5th Edition
ISBN: 9781429275033
Author: Daniel C. Harris
Publisher: Macmillan Higher Education
Question
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Chapter 5, Problem 5.11P

(a)

Interpretation Introduction

Interpretation:

The absorbance detection limit has to be calculated.

Concept introduction:

The signal detection limit is given as follows,

    ydl = yblank + 3s

Here, s is standard deviation.

Standard deviation:

The standard deviation of a random variable X of size n is defined as,

  s = i=1n(xi-x¯)2n-1

where xi is the ith observation and x¯ is the sample mean.

The standard deviation measures the absolute variability of a distribution.

(a)

Expert Solution
Check Mark

Answer to Problem 5.11P

The absorbance detection limit is 3.019×10-3.

Explanation of Solution

The standard deviation value for the 9 given samples is calculated as follows,

    Mean, x¯ = 19[0.0047+0.0054+0.0062+0.0060+0.0046+0.0056+0.0052+0.0044+0.0058]= 0.00532s = (0.0047-0.00532)2+(0.0054-0.00532)2+(0.0062-0.00532)2+(0.0060-0.00532)2(0.0046-0.00532)2+(0.0056-0.00532)2+(0.0052-0.00532)2+(0.0044-0.00532)2+(0.0058-0.00532)28=  0.0000003844+0.0000000064+0.0000007744+0.0000004624+0.0000005184+0.0000000784+0.0000000144+0.0000008464+0.00000023048s= 0.00061

The mean blank value is yblank = 0.001189

The absorbance detection limit is calculated as follows,

    ydl = yblank + 3s= 0.001189+3×0.00061ydl= 3.019×10-3

(b)

Interpretation Introduction

Interpretation:

The concentration detection limit has to be calculated.

Concept Introduction:

The minimum detectable concentration is given as follows,

    Minimum detectable concentration = 3s/m

Here, m is slope and s is standard deviation.

(b)

Expert Solution
Check Mark

Answer to Problem 5.11P

The concentration detection limit value is 8.17×10-8 M.

Explanation of Solution

The concentration detection limit is calculated as follows,

    Minimum detectable concentration = 3s/m3 × 0.000612.24×104 M-1= 8.17×10-8 M

(c)

Interpretation Introduction

Interpretation:

The lower limit of quantitation has to be calculated.

Concept Introduction:

The lower limit of quantitation is given as follows,

    lower limit of quantitation =10sm

Here, s is standard deviation and m is slope.

(c)

Expert Solution
Check Mark

Answer to Problem 5.11P

The lower limit of quantitation is 2.77×10-7 M.

Explanation of Solution

The lower limit of quantitation as follows,

    lower limit of quantitation =10(0.00061)2.20×104 M-1= 2.77×10-7 M

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