Commentary pubs.acs.org/jchemeduc
Name Concepts in Analytical Science Pawel L. Urban* Department of Applied Chemistry, National Chiao Tung University, Hsinchu City 300, Taiwan S Supporting Information *
ABSTRACT: This commentary presents an unconventional view of analytical chemistry as seen through the prism of “name concepts”. First, I provide examples of various analytical methods and phenomena that are referred to by the names of their inventors/discoverers. Second, I suggest that emphasizing name concepts in the analytical chemistry course syllabus can augment student engagement in learning new terms and methods, and it can highlight the problem-solution approach in the field of analytical chemistry. KEYWORDS: First-Year Undergraduate/General, Second-Year Undergraduate, Upper-Division Undergraduate, Analytical Chemistry, History/Philosophy, Bioanalytical Chemistry, Qualitative Analysis, Quantitative Analysis, Mnemonics/Rote Learning
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NAME REACTIONS Organic chemistry literature often discusses so-called “name reactions” to denote the chemical processes that are named after their inventors. There exist books, articles, and Web sites dedicated to name reactions that provide a compendium of knowledge to junior and senior chemists.1,2 Name reactions are instrumental to teaching organic chemistry.3−5 For example, students are taught Diels−Alder addition, Suzuki coupling, and Claisen condensation. When the association between the name and the mechanism is established, these terms are freely used in instruction. The published listings of name reactions constitute a valuable aid for students and researchers in the field of organic synthesis. However, name concepts are not unique to organic chemistry. They are omnipresent in exact sciences. Numerous methods and phenomena in analytical chemistry bear the names of their inventors or discoverers. Brief introductions of the historical background of these methods can increase the interest of students and help them memorize those early applications of chemical analysis. Here, I emphasize the role of name concepts in analytical chemistry, especially in undergraduate training. Table 1 lists possible phases of introducing name concepts in analytical chemistry courses. After establishing the association between the scientific concepts and the names of the inventors/ discoverers, a reference to the concept can be made in further instruction. Eventually, the instructor may capitalize on the story related to the development of the name concept to teach the students the right attitude and scientific approach.
Table 1. Proposed Phases of Introducing Name Concepts to Instruction in the Analytical Chemistry Courses Phase 1
3
Inventor/ discoverer Invention/ discovery Theory
4 5
Applications Reference
6
Implications
2
Description Instructor outlines biography of the scientist behind the concept to be introduced. Instructor describes the essence of the concept. Instructor describes the theoretical and technical details of the concept. Instructor outlines the applications of the concept. Instructor and students refer to the concept by recalling the name of the inventor/discoverer. Instructor capitalizes on the story related to the development of the name concept to teach the students the right attitude and scientific approach.
made significant contributions to analytical science. One of his achievements in this area is the development of an instrument and method for determination of hydrogen and carbon.6 According to his method, organic sample is mineralized in the presence of oxygen at a high temperature. The released volatile compounds further pass through a bed of cuprous oxide and copper to facilitate decomposition of the volatilized sample to simple gases: CO2, H2O, and N2. The water vapor is absorbed by an anhydrous salt, thus enabling the measurement of total hydrogen content. Meanwhile CO2 passes through several tiny vessels filled with potassium hydroxide solution where it is absorbed. The mass increase of this capture solution enables estimation of the total carbon content in the analyzed sample. To facilitate capture of CO2 by the potassium hydroxide solution, the reagent was typically placed inside a triangleshaped tube with 5 spherical chambers, the device called FünfKugel-Apparat or Kaliapparat. A tribute to this, now an obsolete piece of equipment, is given in the logotype of the American Chemical Society. Hermann von Fehling (1812−1885) was one of the many distinguished co-workers of Liebig. Currently,
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FAMOUS NAMES IN ANALYTICAL CHEMISTRY Justus von Liebig (1803−1873) is regarded as one of the most prolific inventors in chemistry. By establishing a teaching laboratory in the University of Giessen, he helped to develop modern chemistry education. For common people in the 19thcentury Europe he was the inventor of the manufacturing method of beef extractthe basis of a popular nutrient-rich meal (“Liebig’s soup”). However, few realize that he has also © 2014 American Chemical Society and Division of Chemical Education, Inc.
Content (Examples)
Published: October 14, 2014 1753
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give false positive results during determination of protein in the milk contaminated with melamine.12 This example can be used in the analytical chemistry course to illustrate how important is the selection of the right methods to address specific analytical tasks. For a few more examples of stories underlying selected name concepts in analytical science, please refer to the Supporting Information. In fact, within the field of analytical chemistry there are numerous methods, laws, formulas, and phenomena which have irreversibly become associated with the names of their inventors and discoverers (Table 2). They can readily be found in handbooks used in undergraduate analytical chemistry courses.13 In fact, they are present in various subdivisions, including elemental analysis, small molecule assays, and genetic testing. They refer to indispensable sample preparation procedures, reagents, and instruments. Therefore, it may be constructive to put emphasis on name concepts while teaching analytical chemistry courses at the undergraduate level. Some of the name concepts are linked to beautiful stories that can be found in popular scientific literature (e.g., the “Classic Kit” series published in the Chemistry World magazine14). They show persistence of the pioneers of chemical analysis and illustrate the problem-solution approach in chemistry. To explore the educational value of name concepts, students may be encouraged by instructors to pursue literature search and present the related background information in their reports from practical classes.
chemistry students all over the world learn about him when they are presented a demonstration of the “Fehling’s test”, which allows one to distinguish glucose from sucrose (used as examples of a reducing and a nonreducing sugar, respectively).7 Liebig and Fehling methods evolved and their primary versions gradually lost their importance. However, they are certainly essential components of undergraduate analytical chemistry course syllabi. Another 19th-century chemist, Johan Kjeldahl (1849−1900), was employed in the Carlsberg Brewery in Copenhagen. His task was to determine the content of protein in cereal grains. The material was more suitable for the production of beer if the content of protein was low. Kjeldahl’s ingenuity led him to the development of a simple four-step protocol: it is based on the digestion of the raw sample in a strong acid, liberation of ammonia, capture of the released ammonia by a weak acid solution, and back-titration of the acid residue (cf. Figure 1).8,9
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CONCLUDING REMARKS
In an effort to make chemistry lectures more attractive to students, it is desirable to find new ways of introducing the course content. Associating concepts with the names of their inventors is just one of many possibilities. Although the names themselves are not suggestive of the scientific ideas, they may facilitate memorizing and recalling numerous phenomena, methods, and principles introduced by the instructor. The field of analytical chemistry contains various name concepts that are already (or can potentially be) incorporated into academic course syllabi. Moreover, introducing name concepts may also foster student engagement in the learning process; for example, students may be asked to research the origin of an invention to find out what it took to solve a specific problem. Overall, it is suggested that using name concepts while teaching analytical chemistry may provide several benefits:
Figure 1. Kjeldahl apparatus. Image from the journal Comptes-rendus des travaux du laboratoire Carlsberg, published by Carlsberg Laboratory (1882−1934). Copyright Carlsberg Archive; used with permission.
The method probes the content of nitrogen in the analyzed samples. Because protein molecules have numerous residues of amine groups (most of which have been converted to peptide bonds), the assay targets the content of nitrogen. The amount of nitrogen is used as a proxy value for the amount of protein.10 The protocol immediately became popular, andin its modern formis used in many industries and research areas. It is instructive that Kjeldahl’s method targeted nitrogen content to quantify protein in order to address a challenging (at that time) task of characterizing raw material for food/beverage production. Therefore, this example may potentially be used to emphasize the strategy of problem-solving in analytical science. Kjeldahl’s method is practical but its misuse can also lead to serious mistakes. In 2008, news broke out that a number of children in China got sickened, which was promptly related to a commercial milk formula.11 It later appeared that the milk was contaminated with melamine additive, a toxic substance. Melamine (MW = 126 g mol−1) has a high content of nitrogen (6 atoms × 14 g mol−1 = 84 g mol−1). However, Kjeldahl’s method cannot distinguish amine-derived nitrogen (in proteins) from other nitrogen-rich moieties; therefore, it may
• Analytical chemistry course content becomes more approachable. • Students get acquainted with the history of science. • Students are taught that chemistry provides solutions to the existing problems (“Necessity is the mother of invention”). • For the students with broad (interdisciplinary) interests, introducing the background of name concepts may make them keen to learn and understand the underlying principles. Although it is likely that using name concepts can enhance analytical chemistry instruction in the undergraduate level, it is appealing to conduct systematic studies on the potential effectiveness of this approach in the educational process. 1754
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Table 2. Representative Name Concepts in Analytical Science Purpose
Examples of Name Concepts (Target/Type)a
Methods of elemental analysis Assays for carbohydrates Assays for amino acids and proteins Assays for other compounds Titration Genomic analysis Proteomic analysis Physical property analysis Chronometric test Metering liquids Reagents Sample preparation Analysis of gases Optical spectroscopy
Dumas (nitrogen), Johnson−Nishita (sulfur), Kjeldahl (nitrogen), Liebig (carbon, hydrogen), Schöniger (flask test, chlorine, nitrogen, sulfur)
Mass spectrometry Electrochemistry Chromatography X-ray diffraction Hydrodynamic size Charged/ionizing particle Microscopy Electronic circuits a
Bial (pentoses), Barfoed (reducing carbohydrates), Benedict (reducing carbohydrates), Fehling (reducing carbohydrates), Molisch (all carbohydrates), Seliwanoff (ketoses), Tollens (aldoses) Bradford (proteins), Guthrie (phenylalanine), Hopkins−Cole (tryptophan), Millon (tyrosine), Lowry (proteins), Sakaguchi (arginine) Brady (aldehydes, ketones), Dragendorff (alkaloids), Dragendorff (bile), Folin (amines), Hinsberg (amines), Jones (aldehydes) Fajans (argentometric), Karl Fischer (water), Mohr (argentometric), Volhard (argentometric) Maxam−Gilbert (sequencing), Sanger (sequencing), Southern (blotting) Edman (degradation) Abbe (refractometer), Thiele (tube) Briggs−Rauscher (ascorbic acid) Ostwald-Folin (pipet), Pasteur (pipet), Van Slyke (pipet) Folin−Ciocalteu (used in Lowry test), Tillmann (ascorbic acid), Zimmermann−Reinhardt (prevent oxidation of Cl−) Bligh−Dyer (extraction), French (pressure cell), Likens−Nickerson (extraction), Schöniger (combustion apparatus), Soxhlet (extraction) Orsat (gas analyzer), Van Slyke (apparatus), Meyer (apparatus), Winkler (test) Beer (law), Bouguer−Lambert−Beer−Walter (law), Czerny−Turner (monochromator), Duboscq (colorimeter), Fabry−Pérot (interferometer), Fourier (transform infrared spectroscope), Golay (cell, detector), Lambert (law), Lyot (filter), Michelson (interferometer), Nernst (glower), Nicol (prism), Raman (spectroscope), Rayleigh (scattering), Smith−Hieftje (background correction), Stokes (shift), Zeeman (background correction) Bainbridge−Jordan (sector analyzer), Daly (detector), Faraday (cup detector), Mattauch−Herzog (sector analyzer), Nier−Johnson (sector analyzer), Nier(-type ion source), Paul (ion trap), Penning (ion trap), Rayleigh (limit), Taylor (cone) Amper(e)((o)meter), Clark (electrode, oxygen), Galvan(i)((o)meter), Heyrovsky (polarograph), Hildebrand (hydrogen electrode), Kohlrausch (law), Volt(a)(meter), Weston (cell) Giddings (formula), Grob (test), Guthrie-Schwartz (restrictor), Hildebrand (solubility parameter), Schoenmakers (rule), Snyder (solvent selectivity triangle) Bragg (law), Laue (camera), Debye−Scherrer (camera) Taylor (dispersion analysis) Auger (electron spectroscope), Geiger−Müller (counter), Mössbauer (spectroscope), Wehnelt (cylinder in electron gun) Nipkow (disk), Rayleigh (criterion) Poggendorff (compensation method), Wheatstone (bridge)
Saxon genitive has not been used for simplicity.
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ASSOCIATED CONTENT
S Supporting Information *
(1) Jones, R. A. Y.; Bunnett, J. F. Nomenclature for organic chemical transformations. Pure Appl. Chem. 1989, 61, 725−768. (2) Organic Chemistry Portal. http://www.organic-chemistry.org/ namedreactions/ (accessed Sep 2014). (3) Castro, C.; Karney, W. Incorporating organic name reactions and minimizing qualitative analysis in an unknown identification experiment. J. Chem. Educ. 1998, 75, 472−475. (4) Dicks, A. P.; Lautens, M.; Koroluk, K. J.; Skonieczny, S. Undergraduate oral examinations in a university organic chemistry curriculum. J. Chem. Educ. 2012, 89, 1506−1510. (5) Lewis, D. E. Organic name reactions: Useful teaching tool or obstructive jargon? http://oasys2.confex.com/acs/231nm/ techprogram/P910962.HTM (accessed July 2014). (6) Liebig, J. Ueber einen neuen Apparat zur Analyse organischer Kö rper, und ü ber die Zusammensetzung einiger organischen Substanzen. Ann. Phys. Chem. (Berlin, Ger.) 1831, 21, 1−43. (7) Fehling, H. Die quantitative Bestimmung von Zucker und Stärkmehl mittelst Kupfervitriol. Justus Liebigs Ann. Chem. 1849, 72, 106−113. (8) Cohen, J. B. Practical Organic Chemistry; MacMillan and Company: London, 1910. (9) Michałowski, T.; Asuero, A. G.; Wybraniec, S. The titration in the Kjeldahl method of nitrogen determination: base or acid as titrant? J. Chem. Educ. 2013, 90, 191−197.
Additional examples of name concepts; Figure S1. This material is available via the Internet at http://pubs.acs.org.
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REFERENCES
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The author declares no competing financial interest.
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ACKNOWLEDGMENTS I thank the Ministry of Science and Technology of Taiwan (formerly, National Science Council; grant no. NSC 102-2113M-009-004-MY2) for the financial support. Thanks are also due to Prof. Yu-Chie Chen as well as four anonymous reviewers.
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DEDICATION With this commentary article, I would like to commemorate Paweł Mazur (from Dab̨ rowa Górnicza, Poland)an inspiring chemistwho passed away at a young age. 1755
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(10) Wiles, P. G.; Gray, I. K.; Kissling, R. C. Routine analysis of proteins by Kjeldahl and Dumas methods: review and interlaboratory study using dairy products. J. AOAC Int. 1998, 81, 620−632. (11) Wong, E. Milk scandal pushes China to set limits on melamine; New York Times, Oct. 8, 2008; http://www.nytimes.com/2008/10/ 09/world/asia/09milk.html?_r=0. (12) CEM Corporation. Overcoming melamine adulteration with accurate protein testing. http://www.cem.de/images/produkte/ protein/Melamine_Flyer_singlepgs.pdf (accessed May 2014). (13) Skoog, D. A.; West, D. M.; Holler, F. J.; Crouch, S. R. Fundamentals of Analytical Chemistry; Brooks/Cole Cengage Learning: Belmont, CA, 2014. (14) The “Classic Kit” series, Chemistry World. http://www.rsc.org/ chemistryworld/more/?type=opinion-classic-kit (accessed Sep 2014).
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