Teaching Students to Think as Analytical Chemists

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Teaching Students to Think as Analytical
Chemists

• David Harvey
• Department of Chemistry
• DePauw University

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Papers/Symposia on Education in Analytical
Chemistry from Journal of Chemical Education

• A Plea for Rationally Coordinated Courses in
  Analytical Chemistry (Brinton, 1924)
• The Training of Analysts (Clarke, 1937)
• Developments in the Teaching of Analytical
  Chemistry (Picketts, 1943)
• Analytical Chemistry - How It Should Be Taught?
  (Bremmer, 1951)
• Education Trends in Analytical Chemistry
  (Symposium, 1960)
• Present Status of the Teaching of Analytical
  Chemistry (Symposium, 1979)
• We Analytical Chemistry Teachers Dont Get No
  Respect (Hirsch, 1987)
• Keeping a Balance in the First Analytical Course
  (Kratochvil, 1991)
• Teaching Analytical Chemistry in the New Century
  (Symposium, 2001)

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What is the Role of Undergraduate Analytical
Chemistry?

• To develop fundamental understanding of
  equilibrium chemistry and laboratory skills in
  solution chemistry?

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What is the Role of Undergraduate Analytical
Chemistry?

• To develop fundamental understanding of
  equilibrium chemistry and laboratory skills in
  solution chemistry?
• To study modern, instrumental analytical
  techniques and applications?

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What is the Role of Undergraduate Analytical
Chemistry?

• To develop fundamental understanding of
  equilibrium chemistry and laboratory skills in
  solution chemistry?
• To study modern, instrumental analytical
  techniques and applications?
• To learn to solve real problems and to work as
  part of small research team?

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On the Importance of Equilibrium and Solution
Chemistry
titrations are still the best way of obtaining
rapid, parts-per-thousand precisionand are
still of importance in industry and commerce..
B. Kratochvil J. Chem. Educ., 1991, 68, 838-839
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On the Importance of Modern Analytical Chemistry
The greatest single pedagogical change is the
impact of instrumental methodsundergraduate
instruction in modern methods of analysis is
becoming an educational responsibility.
P. W. West J. Chem. Educ., 1952, 29, 222-223
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On the Importance of Providing Real Analytical
Problems
In summary, chemical analysis is an applied
science. The teaching of the field must imbue
the applied aspects in the student, and this can
best be done by using real situations.
S. Siggia J. Chem. Educ., 1967, 44, 545-546
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Other Factors at Play in Designing Courses in
Analytical Chemistry

• Departmental Resources
• Instrumentation
• Computational technology
• Budget

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Other Factors at Play in Designing Courses in
Analytical Chemistry

• Departmental Resources
• Instrumentation
• Computational technology
• Budget
• Departmental Curricular Needs
• Where/how is equilibrium chemistry covered?
• Instrumental Analysis Lab vs. Advanced
  Multidisciplinary Lab

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Other Factors at Play in Designing Courses in
Analytical Chemistry

• Departmental Resources
• Instrumentation
• Computational technology
• Budget
• Departmental Curricular Needs
• Where/how is equilibrium chemistry covered?
• Instrumental Analysis Lab vs. Advanced
  Multidisciplinary Lab
• Profile of Students
• Academic strength
• Motivation
• Career goals

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One Thing Upon Which We All Agree There Isnt
Enough Time
How can the professor reap the benefits of
teaching fundamentals while bringing in elements
of problem-based learning without compromising
the former? Available time is a very serious
constraint. The entire formal lecture time in
undergraduate analytical chemistryis about two
and one-half solid 40 hour weeks laboratory time
is equivalent to three to four weeks. Wow!
Thats not much!
R. W. Murray Anal.
Chem. 1998, 70, 425A
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One Thing Upon Which We All Agree There Isnt
Enough Time
How can the professor reap the benefits of
teaching fundamentals while bringing in elements
of problem-based learning without compromising
the former? Available time is a very serious
constraint. The entire formal lecture time in
undergraduate analytical chemistryis about two
and one-half solid 40 hour weeks laboratory time
is equivalent to three to four weeks. Wow!
Thats not much!
R. W. Murray Anal.
Chem. 1998, 70, 425A
The demands upon a students time in the study
of science are growing more severe each year as
the field broadens and the number of subjects
necessary to master in that field increases.
H.
M. P. Brinton J. Chem. Educ. 1924, 1, 226-230
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An Educational Proposition!
If number of topics gtgt available time
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An Educational Proposition!
If number of topics gtgt available time
Then our goal must be to prepare a student to
learn on his or her own
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An Educational Proposition!
If number of topics gtgt available time
Then our goal must be to prepare a student to
learn on his or her own
By teaching our students to think as analytical
chemists
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Can We Teach Students to Think as Analytical
Chemists?
Can we teach analytical thinking? The answer is
that we cannot. It is a thought process and each
individual has a varying thought process.
However, we can exercise the students thought
processes by continually exposing him or her to
real analytical problems during the course of his
or her education.
S. Siggia J. Chem. Educ., 1967, 44, 545-546
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Creating an Environment That Encourages Students
to Think as Analytical Chemists

• What do we mean by real analytical problems?
• Realistic samples (All the World Is a Sample)
• Realistic issues in experimental design

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Creating an Environment That Encourages Students
to Think as Analytical Chemists

• What do we mean by real analytical problems?
• Realistic samples (All the Worlds a Sample)
• Realistic issues in experimental design
• Develop and implement curricular strategies for
  increasing intuitive, critical thinking
• Have students critique analytical methods
• Provide opportunities for Back of the Envelope
  approximations
• Provide unexpected outcomes

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Analytical Chemistry Curriculum at DePauw
University

• As Part of Common Introductory Core
• Chem 260 Thermodynamics, Equilibrium, and
  Kinetics (lab emphasis)
• Courses in Analytical Chemistry
• Chem 351 Chemometrics
• Chem 352 Analytical Equilibria and Separations
• Chem 353 Instrumental Methods
• Chem 450 Method Development (lab course)

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Critiquing Analytical Methods
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Determination of Total Iron in Water and
Wastewater
For samples containing less than 2 ppm Fe,
directly transfer a 50-mL portion to a 125-mL
Erlenmeyer flask. Samples containing more than 2
ppm Fe must be suitably treated before acquiring
the 50-mL portion. Add 2 mL of concentrated HCl
and 1 mL of hydroxylamine to the sample in the
Erlenmeyer flask. Heat the solution to boiling
and continue boiling until the solutions volume
is reduced to between 15 and 20 mL. After
cooling to room temperature, transfer the
solution to a 50-mL volumetric flask, add 10 mL
of an acetate buffer, 2 mL of a 1000 ppm solution
of o-phenanthroline, and dilute to volume. Allow
10-15 min for color development before measuring
the absorbance at 510 nm, using a blank prepared
by carrying 50 mL of distilled water through the
same procedure.
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Critiquing the Analytical Method

• Why are there different directions for treating
  the sample depending on the amount of Fe present?
  What is meant by the statement that samples
  containing more than 2 ppm Fe must be suitably
  treated?
• What is the role of hydroxylamine in this
  procedure and why is such a large excess added?
• Why is it necessary to adjust the pH using an
  acetate buffer?
• Why is it necessary to wait 10-15 min before
  measuring the absorbance?
• The acetate buffer is prepared using ammonium
  acetate and glacial acetic acid. Given that even
  high-quality ammonium acetate is contaminated
  with iron, why isnt this a source of
  interference for this analysis?

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Making Use of Back of the Envelope
Approximations
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Choosing an Analytical Method

• Problem Using an acid/base titration, can you
  find the concentration of a weak acid with a pKa
  of 3 and a nominal concentration of 75 mM in the
  presence of a weak acid with a pKa of 7 and a
  nominal concentration of 25 mM. Assume a sample
  of 5 mL and a titrant that is 0.01 M NaOH.

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Choosing an Analytical Method A Back of the
Envelope Exercise
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Choosing an Analytical Method A Back of the
Envelope Exercise
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Choosing an Analytical Method A Back of the
Envelope Exercise
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Choosing an Analytical Method A Back of the
Envelope Exercise
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Optimizing a Separation

• Problem Find conditions for separating the
  following mixture by capillary zone
  electrophoresis
• 2-aminobenzoic acid (pKa1 2.08, pKa2 4.96)
• benzylamine (pKa 9.35)
• 4-methylphenol (pKa 10.26)

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Optimizing a ProcedureA Back of the Envelope
Exercise
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Providing an Unexpected Result
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Selecting an Appropriate Sample

• The Weakest Link Exercise, Settle, F. A.
  Pleva, M. Anal. Chem. 1999, 71, 538A-540A.
• Students analyze corn chips for Na and evaluate
  contributions of sampling, sample preparation,
  and measurement technique to overall variance
  using a nested experimental design.
• Students predict sampling to be the weakest link.
• Result ? Sampling identified as the weakest link
  (accounting for approximately 80 of overall
  variance).

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Selecting an Appropriate SampleProviding an
Unexpected Outcome

• Sample Erythrosine B coated on NaCl.
• Students predict that sample preparation is the
  weakest link they do not consider sampling to be
  important because sample appears homogeneous.

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Selecting an Appropriate SampleProviding an
Unexpected Outcome

• Result ? Sampling is weakest link (accounting for
  approximately 98 of overall variance).
• Benefits ?Unexpected outcome encourages greater
  appreciation for and awareness of importance of
  sampling students discover that their ability to
  prepare samples is better than they expected.

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Developing an Analytical Method

• Problem Develop a spectrophotometric method for
  determining the concentration of p-nitrophenol in
  aqueous environmental samples.

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Developing an Analytical Method

• Problem Develop a spectrophotometric method for
  determining the concentration of p-nitrophenol in
  aqueous environmental samples.
• Approach of a typical beginning student might be
• Prepare an external standards calibration curve
• Evaluate the calibration curves linearity
• Run a standard sample and evaluate accuracy
• Analyze unknowns and report results

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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Developing an Analytical Method Providing an
Unexpected Outcome
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Acknowledgments

• DePauw University Department of Chemistry
• James and Janet Fisher Fund (DePauw University)
• Faculty Development Fund (DePauw University)
• Neal Abraham (Vice-President for Academic Affairs
  at DePauw University)
• National Science Foundations CCLI Program
• Camille Henry Dreyfus Foundations Special
  Grants Program
• McGraw-Hill Higher Education

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References

• Harvey, D. T. Modern Analytical Chemistry,
  McGraw-Hill, 2000.
• Harvey, D. T. Two Experiments Illustrating the
  Importance of Sampling in a Quantitative Chemical
  Analysis, J. Chem. Educ. 2002, 79, 360-363.
• Harvey, D. T. External Standards or Standard
  Additions Selecting and Validating a Method of
  Standardization, J. Chem. Educ. 2002, 79,
  613-615.