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Teaching Students to Think as Analytical Chemists David Harvey Department of Chemistry DePauw University.

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Presentation on theme: "Teaching Students to Think as Analytical Chemists David Harvey Department of Chemistry DePauw University."— Presentation transcript:

1 Teaching Students to Think as Analytical Chemists David Harvey Department of Chemistry DePauw University

2 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 Don’t Get No Respect (Hirsch, 1987) Keeping a Balance in the First Analytical Course (Kratochvil, 1991) Teaching Analytical Chemistry in the New Century (Symposium, 2001)

3 What is the Role of Undergraduate Analytical Chemistry? To develop fundamental understanding of equilibrium chemistry and laboratory skills in solution chemistry?

4 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?

5 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?

6 On the Importance of Equilibrium and Solution Chemistry “…titrations are still the best way of obtaining rapid, parts- per-thousand precision…[and] are still of importance in industry and commerce..” B. Kratochvil J. Chem. Educ., 1991, 68,

7 On the Importance of Modern Analytical Chemistry “The greatest single pedagogical change is the impact of instrumental methods…undergraduate instruction in modern methods of analysis is becoming an educational responsibility.” P. W. West J. Chem. Educ., 1952, 29,

8 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,

9 Other Factors at Play in Designing Courses in Analytical Chemistry Departmental Resources Instrumentation Computational technology Budget

10 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

11 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

12 One Thing Upon Which We All Agree – There Isn’t 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 chemistry…is about two and one-half solid 40 hour weeks; laboratory time is [equivalent to] three to four weeks. Wow! That’s not much!” R. W. Murray Anal. Chem. 1998, 70, 425A

13 One Thing Upon Which We All Agree – There Isn’t 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 chemistry…is about two and one-half solid 40 hour weeks; laboratory time is [equivalent to] three to four weeks. Wow! That’s not much!” R. W. Murray Anal. Chem. 1998, 70, 425A “The demands upon a student’s 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,

14 If… number of topics >> available time An Educational Proposition!

15 If… number of topics >> available time Then… our goal must be to prepare a student to learn on his or her own An Educational Proposition!

16 If… number of topics >> 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 An Educational Proposition!

17 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 student’s 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,

18 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

19 Creating an Environment That Encourages Students to “Think as Analytical Chemists” What do we mean by “real analytical problems”? Realistic samples (“All the World’s 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

20 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)

21 Critiquing Analytical Methods

22 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 solution’s 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 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.

23 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 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 isn’t this a source of interference for this analysis?

24 Making Use of “Back of the Envelope” Approximations

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

26 Choosing an Analytical Method: A “Back of the Envelope” Exercise

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30 Optimizing a Separation Problem: Find conditions for separating the following mixture by capillary zone electrophoresis: 2-aminobenzoic acid (pK a1 = 2.08, pK a2 = 4.96) benzylamine (pK a = 9.35) 4-methylphenol (pK a = 10.26)

31 Optimizing a Procedure: A “Back of the Envelope” Exercise

32 Providing an Unexpected Result

33 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).

34 Selecting an Appropriate Sample: Providing 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.

35 Selecting an Appropriate Sample: Providing 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.

36 Developing an Analytical Method Problem: Develop a spectrophotometric method for determining the concentration of p-nitrophenol in aqueous environmental samples.

37 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 curve’s linearity Run a standard sample and evaluate accuracy Analyze unknowns and report results

38 Developing an Analytical Method: Providing an Unexpected Outcome

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46 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 Foundation’s CCLI Program Camille & Henry Dreyfus Foundation’s Special Grants Program McGraw-Hill Higher Education

47 References Harvey, D. T. Modern Analytical Chemistry, McGraw- Hill, Harvey, D. T. “Two Experiments Illustrating the Importance of Sampling in a Quantitative Chemical Analysis”, J. Chem. Educ. 2002, 79, Harvey, D. T. “External Standards or Standard Additions: Selecting and Validating a Method of Standardization”, J. Chem. Educ. 2002, 79,


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