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Analytical-Chemistry
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17. xvii
Preface
Preface
Overview
A Organization
B Role of Equilibrium Chemistry
C Computational Software
D How to Use The Electronic Textbook’s Features
E Acknowledgments
F Updates, Ancillary Materials, and Future Editions
G How To Contact the Author
As currently taught in the United States, introductory courses in analytical chemistry
emphasize quantitative (and sometimes qualitative) methods of analysis along with a heavy
dose of equilibrium chemistry. Analytical chemistry, however, is much more than a collection of
analytical methods and an understanding of equilibrium chemistry; it is an approach to solving
chemicalproblems.Althoughequilibriumchemistryandanalyticalmethodsareimportant,their
coverage should not come at the expense of other equally important topics. The introductory
course in analytical chemistry is the ideal place in the undergraduate chemistry curriculum for
exploring topics such as experimental design, sampling, calibration strategies, standardization,
optimization, statistics, and the validation of experimental results. Analytical methods come
and go, but best practices for designing and validating analytical methods are universal. Because
chemistry is an experimental science it is essential that all chemistry students understand the
importance of making good measurements.
My goal in preparing this textbook is to find a more appropriate balance between theory
and practice, between “classical” and “modern” analytical methods, between analyzing samples
and collecting samples and preparing them for analysis, and between analytical methods and
data analysis. There is more material here than anyone can cover in one semester; it is my
hope that the diversity of topics will meet the needs of different instructors, while, perhaps,
suggesting some new topics to cover.
18. xviii Analytical Chemistry 2.1
A Organization
This textbook is organized into four parts. Chapters 1–3 serve as a general
introduction, providing: an overview of analytical chemistry (Chapter 1); a
review of the basic equipment and mathematical tools of analytical chem-
istry, including significant figures, units, and stoichiometry (Chapter 2);
and an introduction to the terminology of analytical chemistry (Chapter
3). Familiarity with this material is assumed throughout the remainder of
the textbook.
Chapters 4–7 cover a number of topics that are important in under-
standing how analytical methods work. Later chapters are mostly indepen-
dent of these chapters, allowing an instructor to choose those topics that
support his or her goals. Chapter 4 provides an introduction to the sta-
tistical analysis of data. Methods for calibrating equipment and standard-
izing methods are covered in Chapter 5, along with a discussion of linear
regression. Chapter 6 provides an introduction to equilibrium chemistry,
stressing both the rigorous solution to equilibrium problems and the use
of semi-quantitative approaches, such as ladder diagrams. The importance
of collecting the right sample, and methods for separating analytes and
interferents are the subjects of Chapter 7.
Chapters 8–13 cover the major areas of analysis, including gravimetry
(Chapter 8), titrimetry (Chapter 9), spectroscopy (Chapter 10), electro-
chemistry (Chapter 11), chromatography and electrophoresis (Chapter 12),
and kinetic methods (Chapter 13). Related techniques, such as acid–base
titrimetry and redox titrimetry, are intentionally gathered together in single
chapters. Combining related techniques in this way encourages students to
see the similarity between methods, rather than focusing on their differ-
ences. The first technique in each chapter is generally that which is most
commonly covered in an introductory course.
Finally, the textbook concludes with two chapters discussing the design
and maintenance of analytical methods, two topics of importance to all ex-
perimental chemists. Chapter 14 considers the development of an analyti-
cal method, including its optimization, its verification, and its validation.
Quality control and quality assessment are discussed in Chapter 15.
B Role of Equilibrium Chemistry
Equilibrium chemistry often receives a significant emphasis in the intro-
ductory analytical chemistry course. Although it is an important topic, an
overemphasis on the computational aspects of equilibrium chemistry may
lead students to confuse analytical chemistry with equilibrium chemistry.
Solving equilibrium problems is important—it is equally important, how-
ever, for students to recognize when such calculations are impractical, or
to recognize when a simpler, more intuitive approach is all they need to
answer a question. For example, in discussing the gravimetric analysis of
Ag+
by precipitating AgCl, there is little point in calculating the equilib-
19. xix
Preface
rium solubility of AgCl because the equilibrium concentration of Cl–
is
rarely known. It is important, however, for students to understand that a
large excess of Cl–
increases the solubility of AgCl due to the formation of
soluble silver–chloro complexes. To balance the presentation of a rigorous
approach to solving equilibrium problems, this textbook also introduces
ladder diagrams as a means for rapidly evaluating the effect of solution
conditions on an analysis. Students are encouraged to use the approach best
suited to the problem at hand.
C Computational Software
Many of the topics in this textbook benefit from the availability of appro-
priate computational software. There are many software packages available
to instructors and students, including spreadsheets (e.g. Excel), numerical
computing environments (e.g. Mathematica, Mathcad, Matlab, R), statisti-
cal packages (e.g. SPSS, Minitab), and data analysis/graphing packages (e.g.
Origin). Because of my familiarity with Excel and R, examples of their use
in solving problems are incorporated into this textbook. Instructors inter-
ested in incorporating other software packages into future editions of this
textbook are encouraged to contact me at harvey@depauw.edu.
D How to Use The Electronic Textbook’s Features
As with any format, an electronic textbook has advantages and disadvan-
tages. Perhaps the biggest disadvantage to an electronic textbook is that
you cannot hold it in your hands (and I, for one, like the feel of book in
my hands when reading) and leaf through it. More specifically, you cannot
mark your place with a finger, flip back several pages to look at a table or
figure, and then return to your reading when you are done. To overcome
this limitation, an electronic textbook can make extensive use of hyperlinks.
Whenever the text refers to an object that is not on the current page—
a figure, a table, an equation, an appendix, a worked example, a practice
exercise—the text is displayed in blue and is underlined. Clicking on the
hyperlink transports you to the relevant object. There are two methods for
returning to your original location within the textbook. When there is no
ambiguity about where to return, such as when reviewing an answer to a
practice exercise, a second text hyperlink is included.
Most objects have links from multiple places within the text, which
means a single return hyperlink is not possible. To return to your original
place select View: Go To: Previous View from the menu bar. If you do not
like to use pull down menus, you can configure the toolbar to include but-
tons for “Previous View” and for “Next View.” To do this, click on View:
Toolbars: More Tools . . ., scroll down to the category for Page Navigation
Tools and check the boxes for Previous View and for Next View. Your
toolbar now includes buttons that you can use to return to your original Click this button to return to your
original position within the text
Although you can use any PDF reader
to read this electronic textbook, the use
of Adobe’s Acrobat Reader is strongly
encouraged. Several features of this elec-
tronic textbook—notably the comment-
ing tools and the inclusion of video—are
available only when using Acrobat Reader
8.0 or later. If you do not have Acrobat
Reader installed on your computer, you
can obtain it from Adobe’s web site.
20. xx Analytical Chemistry 2.1
position within the text. These buttons will appear each time you open the
electronic textbook.
There are several additional hyperlinks to help you navigate within the
electronic textbook. The Table of Contents—both the brief form and the
expanded form—provide hyperlinks to chapters, to main sections, and to
subsections. The “Chapter Overview” on the first page of each chapter pro-
vides hyperlinks to the chapter’s main sections. The textbook’s title, which
appears at the top of each even numbered page, is a hyperlink to the brief
table of contents, and the chapter title, which appears at the top of most
odd numbered pages, is a hyperlink to the chapter’s first page. The collec-
tion of key terms at the end of each chapter are hyperlinks to where the
terms were first introduced, and the key terms in the text are hyperlinks
that return you to the collection of key terms. Taken together, these hyper-
links provide for a easy navigation.
If you are using Adobe Reader, you can configure the program to re-
member where you were when you last closed the electronic textbook. Se-
lect Adobe Reader: Preferences . . . from the menu bar. Select the category
“Documents” and check the box for “Restore last view settings when re-
opening documents.” This is a global change that will affect all documents
that you open using Adobe Reader.
There are two additional features of the electronic textbook that you
may find useful. The first feature is the incorporation of QuickTime and
Flash movies. Some movies are configured to run when the page is dis-
played, and other movies include start, pause, and stop
buttons. If you find that you cannot play a movie check
your permissions. You can do this by selecting Adobe
Reader: Preferences . . . from the menu bar. Choose the
option for “MultimediaTrust” and check the option for
“Allow multimedia operations.” If the permission for
QuickTime or Flash is set to “Never” you can change
it to “Prompt,” which will ask you to authorize the use
of multimedia when you first try to play the movie, or
change it to “Always” if you do not wish to prevent any
files from playing movies.
A second useful feature is the availability of Adobe’s
commenting tools, which allow you to highlight text,
to create text boxes in which you can type notes, to add
sticky notes, and to attach files. You can access the com-
menting tools by selecting Tools: Commenting & Markup from the menu
bar. If you do not like to use the menu bar, you can add tools to the tool
bar by selecting View: Toolbars: Commenting & Markup from the menu
bar. To control what appears on the toolbar, select View: Toolbars: More
Tools . . . and check the boxes for the tools you find most useful. Details on
some of the tools are shown here. You can alter any tool’s properties, such
21. xxi
Preface
as color, by right-clicking on the tool and selecting Tool Default Proper-
ties . . . from the pop-up menu.
These tools allow you to highlight, to under-
line, and to cross out text. Select the tool and
the click and drag over the relevant text.
The text box tool allows you to provide short
annotations to the textbook. Select the tool
and then click and drag to create a text box.
Click in the textbook and type your note.
The sticky note tool is useful when you have a
longer annotation or when you want to make
your annotation easier to see. Click in the
textbook at the spot where you wish to add
the sticky note. Type your entry and the click
the close button to collapse the note into its
icon. Hovering the cursor over the icon dis-
plays the note and clicking on the icon allows
you to edit your note.
The pencil tool allows you to use your mouse
to write notes on the text. The eraser tool al-
lows you to erase notes.
The paperclip tool allows you to attach a file
to the textbook. Select the tool and click in
the textbook at the spot where you wish to
attach the file. Use the browser to find the file
and select OK. The resulting icon is a link to
the file. You can open the file by clicking on
the icon.
E Acknowledgments
This textbook began as a print version published in 2000 by McGraw-
Hill, and the support of the then editorial staff (Jim Smith, Publisher for
Chemistry; Kent Peterson, Sponsoring Editor for Chemistry; Shirley Ober-
broeckling, Developmental Editor for Chemistry; and Jayne Klein, Proj-
ect Manager) is gratefully acknowledged. The assistance of Thomas Timp
(Sponsoring Editor for Chemistry) and Tamara Hodge (Senior Sponsoring
Editor for Chemistry) in returning the copyright to me also is acknowl-
edged. The following individuals kindly reviewed portions of the print ver-
sion as it worked its way through the publication process:
David Ballantine, Northern Illinois University
John Bauer, Illinois State University
Ali Bazzi, University of Michigan–Dearborn
Christopher Harrison, a faculty member
in the Chemistry Department at San Di-
ego State University, has prepared instruc-
tional videos that describe how to use Pre-
view or Adobe Acrobrat Reader to work
with pdf textbooks; you can use the links
to view these videos.
22. xxii Analytical Chemistry 2.1
Steven D. Brown, University of Delaware
Wendy Clevenger, University of Tennessee–Chattanooga
Cathy Cobb, Augusta State University
Paul Flowers, University of North Carolina–Pembroke
George Foy, York College of Pennsylvania
Nancy Gordon, University of Southern Maine
Virginia M. Indivero, Swarthmore College
Michael Janusa, Nicholls State University
J. David Jenkins, Georgia Southern University
David Karpovich, Saginaw Valley State University
Gary Kinsel, University of Texas at Arlington
John McBride, Hoftsra University
Richard S. Mitchell, Arkansas State University
George A. Pearse, Jr., LeMoyne College
Gary Rayson, New Mexico State University
David Redfield, NW Nazarene University
Vincent Remcho, West Virginia University
Jeanette K. Rice, Georgia Southern University
Martin W. Rowe, Texas A&M University
Alexander Scheeline, University of Illinois
James D. Stuart, University of Connecticut
Thomas J. Wenzel, Bates College
David Zax, Cornell University
I am particularly grateful for their detailed comments and suggestions.
Much of what is good in the print edition is the result of their interest and
ideas.
Without the support of DePauw University and its Faculty Develop-
ment Committee, work on this project would not have been possible. This
project began in 1992 with a summer course development grant, and re-
ceived further summer support from the President’s Discretionary Fund.
Portions of the first draft were written during a sabbatical leave in fall 1993.
The second draft was completed with the support of a Fisher Fellowship
in fall 1995. Converting the print version into this electronic version was
completed as part of a year-long sabbatical during the 2008/09 academic
year. A full-year sabbatical during the 2015/16 academic year provided the
time to complete a second edition.
The following faculty members and students graciously provided data
for figures included in this textbook: Bridget Gourley, Jeanette Pope, and
Daniel Scott (DePauw University), Michelle Bushey, Zoe LaPier, Christo-
pher Schardon, and Kyle Meinhardt (Trinity University), and Dwight Stoll,
Jason Schultz, Joanna Berry, and Kaelene Lundstrom (Gustavus Adolphus
College).
I am grateful to the following individuals for their encouragement and
support, for their camaraderie at curricular development workshops, or for
their testing of draft versions of this eText: Cynthia Larive (University of
23. xxiii
Preface
California–Riverside), Ted Kuwana (Kansas), Alex Scheeline (University
of Illinois), Tom Spudich (United States Military Academy), Heather Bul-
len (University of Northern Kentucky), Richard Kelly (East Stroudsburg
University), William Otto (University of Maine–Machias), Alanah Fitch
(Loyola University), Thomas Wenzel (Bates College), Anna Cavinato (East-
ern Oregon University), Steve Petrovic (University of Southern Oregon),
Erin Gross (Creighton University), Mark Vitha (Drake University), Sara
Choung (Point Loma Nazarene University), Michael Setter (John Carroll
University), Corrine Lehr (California Polytechnic State University), Chris-
topher Harrison (San Diego State University), and Bryan Hanson (DePauw
University).
F Updates, Ancillary Materials, and Future Editions
The website for this eText provides access to both the current version of
the textbook (Analytical Chemistry 2.1) and to legacy editions, including
the eText’s illustrations. Also available through the website is a solutions
manual and links to a variety of ancillary materials, including case studies,
Shiny apps, and scripts and packages of functions for use with R. If you are
interested in contributing problems, case studies, data sets, photographs,
figures or any other content, please contact the author at harvey@depauw.
edu.
G How To Contact the Author
Working on this textbook continues to be an interesting challenge and a
rewarding endeavour. One interesting aspect of electronic publishing is that
a book is not static—corrections, new examples and problems, and new
topics are easy to add, and new editions released as needed. I welcome your
input and encourage you to contact me with suggestions for improving this
electronic textbook. You can reach me by e-mail at harvey@depauw.edu.
25. 1
Chapter 1
Introduction to
Analytical Chemistry
Chapter Overview
1A What is Analytical Chemistry?
1B The Analytical Perspective
1C Common Analytical Problems
1D Key Terms
1E Chapter Summary
1F Problems
1G Solutions to Practice Exercises
Chemistryisthestudyofmatter,includingitscomposition,itsstructure,itsphysicalproperties,
and its reactivity. Although there are many ways to study chemistry, traditionally we divide it
into five areas: organic chemistry, inorganic chemistry, biochemistry, physical chemistry, and
analytical chemistry. This division is historical and, perhaps, arbitrary, as suggested by current
interest in interdisciplinary areas, such as bioanalytical chemistry and organometallic chemistry.
Nevertheless, these five areas remain the simplest division that spans the discipline of chemistry.
Each of these traditional areas of chemistry brings a unique perspective to how a chemist
makes sense of the diverse array of elements, ions, and molecules (both small and large) that
make up our physical environment. An undergraduate chemistry course, therefore, is much
more than a collection of facts; it is, instead, the means by which we learn to see the chemical
world from a different perspective. In keeping with this spirit, this chapter introduces you to
the field of analytical chemistry and highlights the unique perspectives that analytical chemists
bring to the study of chemistry.
26. 2 Analytical Chemistry 2.1
1A What is Analytical Chemistry?
“Analytical chemistry is what analytical chemists do.”
Let’s begin with a deceptively simple question: What is analytical chemis-
try? Like all areas of chemistry, analytical chemistry is so broad in scope and
so much in flux that it is difficult to find a simple definition more revealing
than that quoted above. In this chapter we will try to expand upon this
simple definition by saying a little about what analytical chemistry is, as
well as a little about what analytical chemistry is not.
Analytical chemistry often is described as the area of chemistry respon-
sible for characterizing the composition of matter, both qualitatively (Is
there lead in this paint chip?) and quantitatively (How much lead is in this
paint chip?). As we shall see, this description is misleading.
Most chemists routinely make qualitative and quantitative measure-
ments. For this reason, some scientists suggest that analytical chemistry is
not a separate branch of chemistry, but simply the application of chemical
knowledge.1
In fact, you probably have performed many such quantitative
and qualitative analyses in other chemistry courses.
Defining analytical chemistry as the application of chemical knowledge
ignores the unique perspective that an analytical chemist bring to the study
of chemistry. The craft of analytical chemistry is found not in performing a
routine analysis on a routine sample—a task we appropriately call chemical
analysis—but in improving established analytical methods, in extending
these analytical methods to new types of samples, and in developing new
analytical methods to measure chemical phenomena.2
Here is one example of the distinction between analytical chemistry
and chemical analysis. A mining engineers evaluates an ore by comparing
the cost of removing the ore from the earth with the value of its contents,
which they estimate by analyzing a sample of the ore. The challenge of
developing and validating a quantitative analytical method is the analyti-
cal chemist’s responsibility; the routine, daily application of the analytical
method is the job of the chemical analyst.
Another difference between analytical chemistry and chemical analysis
is that an analytical chemist works to improve and to extend established
analytical methods. For example, several factors complicate the quantita-
tive analysis of nickel in ores, including nickel’s unequal distribution within
the ore, the ore’s complex matrix of silicates and oxides, and the presence of
other metals that may interfere with the analysis. Figure 1.1 outlined one
standard analytical method in use during the late nineteenth century.3
The
need for many reactions, digestions, and filtrations makes this analytical
method both time-consuming and difficult to perform accurately.
1 Ravey, M. Spectroscopy, 1990, 5(7), 11.
2 de Haseth, J. Spectroscopy, 1990, 5(7), 11.
3 Fresenius. C. R. A System of Instruction in Quantitative Chemical Analysis; John Wiley and Sons:
New York, 1881.
This quote is attributed to C. N. Reilly
(1925-1981) on receipt of the 1965 Fish-
er Award in Analytical Chemistry. Reilly,
who was a professor of chemistry at the
University of North Carolina at Cha-
pel Hill, was one of the most influential
analytical chemists of the last half of the
twentieth century.
You might, for example, have determined
the concentration of acetic acid in vinegar
using an acid–base titration, or used a qual
scheme to identify which of several metal
ions are in an aqueous sample.
Seven Stages of an Analytical Method
1. Conception of analytical method
(birth).
2. Successful demonstration that the
analytical method works.
3. Establishment of the analytical meth-
od’s capabilities.
4. Widespread acceptance of the analyti-
cal method.
5. Continued development of the ana-
lytical method leads to significant im-
provements.
6. New cycle through steps 3–5.
7. Analytical method can no longer com-
pete with newer analytical methods
(death).
Steps 1–3 and 5 are the province of ana-
lytical chemistry; step 4 is the realm of
chemical analysis.
The seven stages of an analytical method
listed here are modified from Fassel, V.
A. Fresenius’ Z. Anal. Chem. 1986, 324,
511–518 and Hieftje, G. M. J. Chem.
Educ. 2000, 77, 577–583.
For another view of what constitutes
analytical chemistry, see the article “Quo
Vadis, Analytical Chemistry?”, the full
reference for which is Valcárcel, M. Anal.
Bioanal. Chem. 2016, 408, 13-21.
27. 3
Chapter 1 Introduction to Analytical Chemistry
Figure 1 .1 Fresenius’ analytical scheme for the gravimetric analysis of Ni in ores. After each
step, the solid and the solution are separated by gravity filtration. Note that the mass of
nickel is not determined directly. Instead, Co and Ni first are isolated and weighed together
(mass A), and then Co is isolated and weighed separately (mass B). The timeline shows
that it takes approximately 58 hours to analyze one sample. This scheme is an example of
a gravimetric analysis, which is explored further in Chapter 8.
Original Sample
PbSO4; Sand
1:3 H2SO4/HNO3, 100°C for 8-10 hrs
dilute w/H2O, digest for 2-4 hr
Cu2+, Fe3+, Co2+, Ni2+
dilute; bubble H2S(g)
CuS
Fe3+, Co2+, Ni2+
cool, add NH3
digest 50o-70o for 30 min
Fe(OH)3 Co2+, Ni2+
HCl
Fe3+
neutralize w/NH3
add Na2CO3, CH3COOH
basic ferric acetate
Waste
slightly acidify w/HCl
heat, bubble H2S(g)
CoS, NiS
add aqua regia and heat
add HCl until strongly acidic
bubble H2S(g)
Co2+, Ni2+ CuS, PbS
Waste
Co(OH)2, Ni(OH)2
heat
add Na2CO3 until alkaline
add NaOH
Co, Ni
heat; H2(g)
add HNO3, K2CO3, KNO3,
and CH3COOH and digest for 24 hours
Ni2+ K3Co(NO3)5
add dilute HCl
Waste
Co2+
Co
follow procedure
from point * above
*
Solids
Solutions
mass A
%Ni = mass A - mass B
mass sample
x 100
mass B
key
Approximate
Elapsed
Time
14 hours
16 hours
17 hours
20 hours
22 hours
23 hours
26 hours
51 hours
54 hours
58 hours
Start
28. 4 Analytical Chemistry 2.1
dimethylglyoxime
The discovery, in 1905, that dimethylglyoxime (dmg) selectively precip-
itates Ni2+
and Pd2+
led to an improved analytical method for the quantita-
tive analysis of nickel.4
The resulting analysis, which is outlined in Figure
1.2, requires fewer manipulations and less time. By the 1970s, flame atomic
absorption spectrometry replaced gravimetry as the standard method for
analyzing nickel in ores,5
resulting in an even more rapid analysis. Today,
the standard analytical method utilizes an inductively coupled plasma opti-
cal emission spectrometer.
Perhaps a more appropriate description of analytical chemistry is “the
science of inventing and applying the concepts, principles, and…strategies
for measuring the characteristics of chemical systems.”6
Analytical chem-
ists often work at the extreme edges of analysis, extending and improving
4 Kolthoff, I. M.; Sandell, E. B. Textbook of Quantitative Inorganic Analysis, 3rd Ed., The Macmil-
lan Company: New York, 1952.
5 Van Loon, J. C. Analytical Atomic Absorption Spectroscopy, Academic Press: New York, 1980.
6 Murray, R. W. Anal. Chem. 1991, 63, 271A.
Figure 1 .2 Gravimetric analysis for Ni in ores by precipitating Ni(dmg)2
. The timeline shows that
it takes approximately 18 hours to analyze a single sample, substantially less than 58 hours for the
method in Figure 1.1. The factor of 0.2301 in the equation for %Ni accounts for the difference in
the formula weights of Ni and Ni(dmg)2
; see Chapter 8 for further details.
Solids
Solutions
Original Sample
HNO3
, HCl, heat
Residue Solution
20% NH4
Cl
10% tartaric acid
make alkaline w/ 1:1 NH3
Is
solid
present?
yes
no
make acidic w/ HCl
1% alcoholic dmg
make alkaline w/ 1:1 NH3
Ni(dmg)2
mass A
%Ni = mass A x 0.2031
mass sample
x 100
Approximate
Elapsed
Time
Start
18 hours
14 hours
key
N
OH
CH3
CH3
N
HO
29. 5
Chapter 1 Introduction to Analytical Chemistry
the ability of all chemists to make meaningful measurements on smaller
samples, on more complex samples, on shorter time scales, and on species
present at lower concentrations. Throughout its history, analytical chemis-
try has provided many of the tools and methods necessary for research in
other traditional areas of chemistry, as well as fostering multidisciplinary
research in, to name a few, medicinal chemistry, clinical chemistry, toxicol-
ogy, forensic chemistry, materials science, geochemistry, and environmental
chemistry.
You will come across numerous examples of analytical methods in this
textbook, most of which are routine examples of chemical analysis. It is
important to remember, however, that nonroutine problems prompted
analytical chemists to develop these methods.
1B The Analytical Perspective
Having noted that each area of chemistry brings a unique perspective to the
study of chemistry, let’s ask a second deceptively simple question: What is
the analytical perspective? Many analytical chemists describe this perspec-
tive as an analytical approach to solving problems.7
Although there likely
are as many descriptions of the analytical approach as there are analytical
chemists, it is convenient to define it as the five-step process shown in
Figure 1.3.
Three general features of this approach deserve our attention. First, in
steps 1 and 5 analytical chemists have the opportunity to collaborate with
individuals outside the realm of analytical chemistry. In fact, many prob-
lems on which analytical chemists work originate in other fields. Second,
the heart of the analytical approach is a feedback loop (steps 2, 3, and 4)
in which the result of one step requires that we reevaluate the other steps.
Finally, the solution to one problem often suggests a new problem.
Analytical chemistry begins with a problem, examples of which include
evaluating the amount of dust and soil ingested by children as an indica-
tor of environmental exposure to particulate based pollutants, resolving
contradictory evidence regarding the toxicity of perfluoro polymers during
combustion, and developing rapid and sensitive detectors for chemical and
biological weapons. At this point the analytical approach involves a collabo-
ration between the analytical chemist and the individual or agency working
on the problem. Together they determine what information is needed and
clarify how the problem relates to broader research goals or policy issues,
both essential to the design of an appropriate experimental procedure.
To design the experimental procedure the analytical chemist considers
criteria, such as the required accuracy, precision, sensitivity, and detection
7 For different viewpoints on the analytical approach see (a) Beilby, A. L. J. Chem. Educ. 1970, 47,
237-238; (b) Lucchesi, C. A. Am. Lab. 1980, October, 112-119; (c) Atkinson, G. F. J. Chem.
Educ. 1982, 59, 201-202; (d) Pardue, H. L.; Woo, J. J. Chem. Educ. 1984, 61, 409-412; (e)
Guarnieri, M. J. Chem. Educ. 1988, 65, 201-203, (f) Strobel, H. A. Am. Lab. 1990, October,
17-24.
These examples are taken from a series
of articles, entitled the “Analytical Ap-
proach,” which for many years was a
regular feature of the journal Analytical
Chemistry.
To an analytical chemist, the process of
making a useful measurement is critical; if
the measurement is not of central impor-
tance to the work, then it is not analytical
chemistry.
An editorial in Analytical Chemistry en-
titled “Some Words about Categories
of Manuscripts” highlights nicely what
makes a research endeavour relevant to
modern analytical chemistry. The full ci-
tation is Murray, R. W. Anal. Chem. 2008,
80, 4775; for a more recent editorial, see
“The Scope of Analytical Chemistry” by
Sweedler, J. V. et. al. Anal. Chem. 2015,
87, 6425.
Chapter 3 introduces you to the language
of analytical chemistry. You will find terms
such accuracy, precision, and sensitivity
defined there.
30. 6 Analytical Chemistry 2.1
limit, the urgency with which results are needed, the cost of a single analysis,
the number of samples to analyze, and the amount of sample available for
analysis. Finding an appropriate balance between these criteria frequently
is complicated by their interdependence. For example, improving precision
may require a larger amount of sample than is available. Consideration
also is given to how to collect, store, and prepare samples, and to whether
chemical or physical interferences will affect the analysis. Finally a good
experimental procedure may yield useless information if there is no method
for validating the results.
The most visible part of the analytical approach occurs in the labora-
tory. As part of the validation process, appropriate chemical and physical
standards are used to calibrate equipment and to standardize reagents.
The data collected during the experiment are then analyzed. Frequently
the data first is reduced or transformed to a more readily analyzable form
and then a statistical treatment of the data is used to evaluate accuracy and
precision, and to validate the procedure. Results are compared to the origi-
nal design criteria and the experimental design is reconsidered, additional
trials are run, or a solution to the problem is proposed. When a solution is
proposed, the results are subject to an external evaluation that may result
in a new problem and the beginning of a new cycle.
See Chapter 7 for a discussion of how
to collect, store, and prepare samples for
analysis.
See Chapter 14 for a discussion about how
to validate an analytical method. Calibra-
tion and standardization methods, includ-
ing a discussion of linear regression, are
covered in Chapter 5.
Figure 1 .3 Flow diagram showing one view of the analytical approach to solving problems (modified
after Atkinson.7c
Step 1. Identify and Define Problem
What is the problem’s context?
What type of information is needed?
Step 5. Propose Solution to Problem
Is the answer sufficient?
Does answer suggest a new problem?
Step 2. Design Experimental Procedure
Establish design criteria.
Identify potential interferents.
Establish validation criteria.
Select analytical method.
Establish sampling strategy.
Step 4. Analyze Experimental Data
Reduce and transform data.
Complete statistical analysis.
Verify results.
Interpret results.
Step 3. Conduct Experiment & Gather Data
Calibrate instruments and equipment.
Standardize reagents.
Gather data.
Feedback
Loop
Chapter 4 introduces the statistical analy-
sis of data.
31. 7
Chapter 1 Introduction to Analytical Chemistry
Use this link to access the article’s abstract
from the journal’s web site. If your institu-
tion has an on-line subscription you also
will be able to download a PDF version
of the article.
As noted earlier some scientists question whether the analytical ap-
proach is unique to analytical chemistry.Here, again, it helps to distinguish
between a chemical analysis and analytical chemistry. For an analytically-
oriented scientist, such as a physical organic chemist or a public health
officer, the primary emphasis is how the analysis supports larger research
goals that involve fundamental studies of chemical or physical processes,
or that improve access to medical care. The essence of analytical chemistry,
however, is in developing new tools for solving problems, and in defining
the type and quality of information available to other scientists.
1C Common Analytical Problems
Many problems in analytical chemistry begin with the need to identify
what is present in a sample. This is the scope of a qualitative analysis,
examples of which include identifying the products of a chemical reaction,
Practice Exercise 1.1
As an exercise, let’s adapt our model of the analytical approach to the
development of a simple, inexpensive, portable device for completing
bioassays in the field. Before continuing, locate and read the article
“Simple Telemedicine for Developing Regions: Camera Phones and
Paper-Based Microfluidic Devices for Real-Time, Off-Site Diagnosis”
by Andres W. Martinez, Scott T. Phillips, Emanuel Carriho, Samuel W.
Thomas III, Hayat Sindi, and George M. Whitesides. You will find it on
pages 3699-3707 in Volume 80 of the journal Analytical Chemistry, which
was published in 2008. As you read the article, pay particular attention
to how it emulates the analytical approach and consider the following
questions:
What is the analytical problem and why is it important?
What criteria did the authors consider in designing their experiments?
What is the basic experimental procedure?
What interferences were considered and how did they overcome them?
How did the authors calibrate the assay?
How did the authors validate their experimental method?
Is there evidence that steps 2, 3, and 4 are repeated?
Was there a successful conclusion to the analytical problem?
Don’t let the technical details in the paper overwhelm you; if you skim
over these you will find the paper both well-written and accessible.
Click here to review your answers to these questions.
This exercise provides you with an op-
portunity to think about the analytical
approach in the context of a real analyti-
cal problem. Practice exercises such as this
provide you with a variety of challenges
ranging from simple review problems to
more open-ended exercises. You will find
answers to practice exercises at the end of
each chapter.
32. 8 Analytical Chemistry 2.1
screening an athlete’s urine for a performance-enhancing drug, or deter-
mining the spatial distribution of Pb on the surface of an airborne par-
ticulate. An early challenge for analytical chemists was developing simple
chemical tests to identify inorganic ions and organic functional groups. The
classical laboratory courses in inorganic and organic qualitative analysis,
still taught at some schools, are based on this work.8
Modern methods for
qualitative analysis rely on instrumental techniques, such as infrared (IR)
spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and mass
spectrometry (MS). Because these qualitative applications are covered ade-
quately elsewhere in the undergraduate curriculum, they receive no further
consideration in this text.
Perhaps the most common analytical problem is a quantitative analy-
sis, examples of which include the elemental analysis of a newly synthesized
compound, measuring the concentration of glucose in blood, or determin-
ing the difference between the bulk and the surface concentrations of Cr
in steel. Much of the analytical work in clinical, pharmaceutical, environ-
mental, and industrial labs involves developing new quantitative methods
to detect trace amounts of chemical species in complex samples. Most of
the examples in this text are of quantitative analyses.
Another important area of analytical chemistry, which receives some
attention in this text, are methods for characterizing physical and chemi-
cal properties. The determination of chemical structure, of equilibrium
constants, of particle size, and of surface structure are examples of a char-
acterization analysis.
The purpose of a qualitative, a quantitative, or a characterization analy-
sis is to solve a problem associated with a particular sample. The purpose
of a fundamental analysis, on the other hand, is to improve our under-
standing of the theory that supports an analytical method and to under-
stand better an analytical method’s limitations.
1D Key Terms
characterization analysis fundamental analysis qualitative analysis
quantitative analysis
1E Chapter Summary
Analytical chemists work to improve the ability of chemists and other sci-
entists to make meaningful measurements. The need to work with smaller
samples, with more complex materials, with processes occurring on shorter
time scales, and with species present at lower concentrations challenges
8 See, for example, the following laboratory texts: (a) Sorum, C. H.; Lagowski, J. J. Introduction
to Semimicro Qualitative Analysis, 5th Ed.; Prentice-Hall: Englewood, NJ, 1977; (b) Shriner, R.
L.; Fuson, R. C.; Curtin, D. Y. The Systematic Identification of Organic Compounds, 5th Ed.; John
Wiley and Sons: New York, 1964.
A good resource for current examples of
qualitative, quantitative, characterization,
and fundamental analyses is Analytical
Chemistry’s annual review issue that high-
lights fundamental and applied research
in analytical chemistry. Examples of re-
view articles in the 2015 issue include
“Analytical Chemistry in Archaeological
Research,” “Recent Developments in Pa-
per-Based Microfluidic Devices,” and “Vi-
brational Spectroscopy: Recent Develop-
ments to Revolutionize Forensic Science.”
33. 9
Chapter 1 Introduction to Analytical Chemistry
analytical chemists to improve existing analytical methods and to develop
new ones.
Typical problems on which analytical chemists work include qualitative
analyses (What is present?), quantitative analyses (How much is present?),
characterization analyses (What are the sample’s chemical and physical
properties?), and fundamental analyses (How does this method work and
how can it be improved?).
1F Problems
1. For each of the following problems indicate whether its solution re-
quires a qualitative analysis, a quantitative analysis, a characterization
analysis, and/or a fundamental analysis. More than one type of analysis
may be appropriate for some problems.
(a) The residents in a neighborhood near a hazardous-waste disposal
site are concerned that it is leaking contaminants into their ground-
water.
(b) An art museum is concerned that a recently acquired oil painting is
a forgery.
(c) Airport security needs a more reliable method for detecting the
presence of explosive materials in luggage.
(d) The structure of a newly discovered virus needs to be determined.
(e) A new visual indicator is needed for an acid–base titration.
(f) A new law requires a method for evaluating whether automobiles
are emitting too much carbon monoxide.
2. Read the article “When MachineTastes Coffee: Instrumental Approach
to Predict the Sensory Profile of Espresso Coffee,” which discusses work
completed at the Nestlé Research Center in Lausanne, Switzerland. You
will find the article on pages 1574-1581 in Volume 80 of Analytical
Chemistry, published in 2008. Prepare an essay that summarizes the
nature of the problem and how it was solved. Do not worry about the
nitty-gritty details of the mathematical model developed by the authors,
which relies on a combination of an analysis of variance (ANOVA), a
topic we will consider in Chapter 14, and a principle component regres-
sion (PCR), at topic that we will not consider in this text. Instead, focus
on the results of the model by examining the visualizations in Figures
3 and 4. As a guide, refer to Figure 1.3 in this chapter for a model of
the analytical approach to solving problems.
Use this link to access the article’s abstract
from the journal’s web site. If your institu-
tion has an on-line subscription you also
will be able to download a PDF version
of the article.
34. 10 Analytical Chemistry 2.1
1G Solutions to Practice Exercises
Practice Exercise 1.1
What is the analytical problem and why is it important?
A medical diagnoses often relies on the results of a clinical analysis. When a
patient visits a doctor, he or she may draw a sample of your blood and send
it to the lab for analysis. In some cases the result of the analysis is available in
10-15 minutes. What is possible in a developed country, such as the United
States, may not be feasible in a country with less access to expensive lab
equipment and with fewer trained personnel available to run the tests and
to interpret the results. The problem addressed in this paper, therefore, is
the development of a reliable device for rapidly performing a clinical assay
under less than ideal circumstances.
What criteria did the authors consider in designing their experiments?
In considering a solution to this problem, the authors identify seven impor-
tant criteria for the analytical method: it must be inexpensive; it must oper-
ate without the need for much electricity, so that it can be used in remote
locations; it must be adaptable to many types of assays; its must not require
a highly skilled technician; it must be quantitative; it must be accurate; and
it must produce results rapidly.
What is the basic experimental procedure?
The authors describe how they developed a paper-based microfluidic device
that allows anyone to run an analysis simply by dipping the device into a
sample (synthetic urine, in this case). The sample moves by capillary action
into test zones containing reagents that react with specific species (glucose
and protein, for this prototype device). The reagents react to produce a
color whose intensity is proportional to the species’ concentration. A digital
photograph of the microfluidic device is taken using a cell phone camera
and sent to an off-site physician who uses image editing software to analyze
the photograph and to interpret the assay’s result.
What interferences were considered and how did they overcome them?
In developing this analytical method the authors considered several chemi-
cal or physical interferences. One concern was the possibility of non-specif-
ic interactions between the paper and the glucose or protein, which might
lead to non-uniform image in the test zones. A careful analysis of the dis-
tribution of glucose and protein in the text zones showed that this was not
a problem. A second concern was the possibility that particulate materials
in the sample might interfere with the analyses. Paper is a natural filter for
particulate materials and the authors found that samples containing dust,
sawdust, and pollen do not interfere with the analysis for glucose. Pollen,
This is an example of a colorimetric meth-
od of analysis. Colorimetric methods are
covered in Chapter 10.
35. 11
Chapter 1 Introduction to Analytical Chemistry
however, is an interferent for the protein analysis, presumably because it,
too, contains protein.
How did the author’s calibrate the assay?
To calibrate the device the authors analyzed a series of standard solutions
that contained known concentrations of glucose and protein. Because an
image’s intensity depends upon the available light, a standard sample is run
with the test samples, which allows a single calibration curve to be used for
samples collected under different lighting conditions.
How did the author’s validate their experimental method?
The test device contains two test zones for each analyte, which allows for
duplicate analyses and provides one level of experimental validation. To
further validate the device, the authors completed 12 analyses at each of
three known concentrations of glucose and protein, obtaining acceptable
accuracy and precision in all cases.
Is there any evidence of repeating steps 2, 3, and 4?
Developing this analytical method required several cycles through steps 2,
3, and 4 of the analytical approach. Examples of this feedback loop include
optimizing the shape of the test zones and evaluating the importance of
sample size.
Was there a successful conclusion to the analytical problem?
Yes. The authors were successful in meeting their goals by developing and
testing an inexpensive, portable, and easy-to-use device for running clinical
samples in developing countries.
Click here to return to the chapter.