BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213
BuyFind

Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

Solutions

Chapter 15, Problem 15.7QAP
Interpretation Introduction

(a)

Interpretation:

The calibration curve should be constructed in a spread sheet.

Concept introduction:

A calibration curve or standard curve is a method used in analytical chemistry to determine the concentration of unknown sample by comparing to a set of samples with known concentrations.

Interpretation Introduction

(b)

Interpretation:

The least square slope and the intercept for the plot in (a) should be determined.

Concept introduction:

Syy=(yiy¯)2Sxx=(xix¯)2Sxy=(xix¯)(yiy¯)

The slope of the line, m=SxySxx

The intercept, b=y¯mx¯

Interpretation Introduction

(c)

Interpretation:

The standard deviation of the slope and the standard deviation about regression for the curve should be determined.

Concept introduction:

Standard deviation about regression, sr=Syym2SxxN2

N − number of points used.

The standard deviation of the slope, sm=sr2Sxx

The standard deviation of the intercept, sb=srxi2Nxi2(xi)2

Interpretation Introduction

(d)

Interpretation:

The concentration of unknown NADH sample should be calculated using the spreadsheet.

Concept introduction:

A calibration curve or standard curve is a method used in analytical chemistry to determine the concentration of unknown sample by comparing to a set of samples with known concentrations.

Interpretation Introduction

(e)

Interpretation:

The relative standard deviation for the result in part (d) should be calculated.

Concept introduction:

Standard deviation of the results obtained from the calibration curve = sc=srm1M+1N+(y¯cy¯)2m2Sxx

M − number of replicates

N- number of calibration points.

RSD=sx×100

RSD − relative standard deviation

x - mean of x values

s − standard deviation

Interpretation Introduction

(f)

Interpretation:

The relative standard deviation for the result in part (d) should be calculated if a result of 7.95 was the mean of three measurements.

Concept introduction:

Standard deviation of the results obtained from the calibration curve = sc=srm1M+1N+(y¯cy¯)2m2Sxx

M − number of replicates

N- number of calibration points.

RSD=sx×100

RSD − relative standard deviation

x - mean of x values

s − standard deviation

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