D. Harvey - Modern Analytical Chemistry (794078), страница 7
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Finally, many analytical chemists engage in fundamentalstudies of analytical methods. In this section we briefly discuss each of these fourareas of analysis.Many problems in analytical chemistry begin with the need to identify what ispresent in a sample. This is the scope of a qualitative analysis, examples of whichinclude identifying the products of a chemical reaction, screening an athlete’s urinefor the presence of a performance-enhancing drug, or determining the spatial distribution of Pb on the surface of an airborne particulate. Much of the early work inanalytical chemistry involved the development of simple chemical tests to identifythe presence of inorganic ions and organic functional groups. The classical laboratory courses in inorganic and organic qualitative analysis,9 still taught at someschools, are based on this work.
Currently, most qualitative analyses use methodssuch as infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry.These qualitative applications of identifying organic and inorganic compounds arecovered adequately elsewhere in the undergraduate curriculum and, so, will receiveno further consideration in this text.1400-CH01 9/9/99 2:20 PM Page 9Chapter 1 IntroductionPerhaps the most common type of problem encountered in the analytical lab isa quantitative analysis.
Examples of typical quantitative analyses include the elemental analysis of a newly synthesized compound, measuring the concentration ofglucose in blood, or determining the difference between the bulk and surface concentrations of Cr in steel. Much of the analytical work in clinical, pharmaceutical,environmental, and industrial labs involves developing new methods for determining the concentration of targeted species in complex samples. Most of the examplesin this text come from the area of quantitative analysis.Another important area of analytical chemistry, which receives some attentionin this text, is the development of new methods for characterizing physical andchemical properties.
Determinations of chemical structure, equilibrium constants,particle size, and surface structure are examples of a characterization analysis.The purpose of a qualitative, quantitative, and characterization analysis is tosolve a problem associated with a sample. A fundamental analysis, on the otherhand, is directed toward improving the experimental methods used in the otherareas of analytical chemistry.
Extending and improving the theory on which amethod is based, studying a method’s limitations, and designing new and modifying old methods are examples of fundamental studies in analytical chemistry.9quantitative analysisAn analysis in which we determine howmuch of a constituent species is presentin a sample.characterization analysisAn analysis in which we evaluate asample’s chemical or physical properties.fundamental analysisAn analysis whose purpose is to improvean analytical method’s capabilities.1D KEY TERMScharacterization analysis (p. 9)fundamental analysis (p. 9)qualitative analysis(p. 8)quantitative analysis(p.
9)1E SUMMARYAnalytical chemists work to improve the ability of all chemists tomake meaningful measurements. Chemists working in medicinalchemistry, clinical chemistry, forensic chemistry, and environmental chemistry, as well as the more traditional areas of chemistry, need better tools for analyzing materials. The need to workwith smaller quantities of material, with more complex materials, with processes occurring on shorter time scales, and withspecies present at lower concentrations challenges analyticalchemists to improve existing analytical methods and to developnew analytical techniques.Typical problems on which analytical chemists work includequalitative analyses (what is present?), quantitative analyses(how much is present?), characterization analyses (what arethe material’s chemical and physical properties?), and fundamental analyses (how does this method work and how can it beimproved?).1F PROBLEMS1.
For each of the following problems indicate whether itssolution requires a qualitative, quantitative, characterization,or fundamental study. More than one type of analysis may beappropriate for some problems.a. A hazardous-waste disposal site is believed to be leakingcontaminants into the local groundwater.b. An art museum is concerned that a recent acquisition is aforgery.c. A more reliable method is needed by airport security fordetecting the presence of explosive materials in luggage.d. The structure of a newly discovered virus needs to bedetermined.e.
A new visual indicator is needed for an acid–base titration.f. A new law requires a method for evaluating whetherautomobiles are emitting too much carbon monoxide.2. Read a recent article from the column “Analytical Approach,”published in Analytical Chemistry, or an article assigned byyour instructor, and write an essay summarizing the nature ofthe problem and how it was solved. As a guide, refer back toFigure 1.3 for one model of the analytical approach.1400-CH01 9/9/99 2:20 PM Page 1010Modern Analytical Chemistry1G SUGGESTED READINGSThe role of analytical chemistry within the broader discipline ofchemistry has been discussed by many prominent analyticalchemists.
Several notable examples follow.Baiulescu, G. E.; Patroescu, C.; Chalmers, R. A. Education andTeaching in Analytical Chemistry. Ellis Horwood: Chichester,1982.Hieftje, G. M. “The Two Sides of Analytical Chemistry,” Anal.Chem. 1985, 57, 256A–267A.Kissinger, P. T. “Analytical Chemistry—What is It? Who Needs It?Why Teach It?” Trends Anal.
Chem. 1992, 11, 54–57.Laitinen, H. A. “Analytical Chemistry in a Changing World,”Anal. Chem. 1980, 52, 605A–609A.Laitinen, H. A. “History of Analytical Chemistry in the U.S.A.,”Talanta 1989, 36, 1–9.Laitinen, H. A.; Ewing, G. (eds). A History of AnalyticalChemistry. The Division of Analytical Chemistry of theAmerican Chemical Society: Washington, D.C., 1972.McLafferty, F.
W. “Analytical Chemistry: Historic and Modern,”Acc. Chem. Res. 1990, 23, 63–64.Mottola, H. A. “The Interdisciplinary and MultidisciplinaryNature of Contemporary Analytical Chemistry and Its CoreComponents,” Anal. Chim. Acta 1991, 242, 1–3.Tyson, J. Analysis: What Analytical Chemists Do. Royal Society ofChemistry: Cambridge, England, 1988.Several journals are dedicated to publishing broadly in thefield of analytical chemistry, including Analytical Chemistry,Analytica Chimica Acta, Analyst, and Talanta.
Other journals, toonumerous to list, are dedicated to single areas of analyticalchemistry.Current research in the areas of quantitative analysis, qualitativeanalysis, and characterization analysis are reviewed biannually(odd-numbered years) in Analytical Chemistry’s “ApplicationReviews.”Current research on fundamental developments in analyticalchemistry are reviewed biannually (even-numbered years) inAnalytical Chemistry’s “Fundamental Reviews.”1H REFERENCES1. 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 ChemicalAnalysis. John Wiley and Sons: New York, 1881.4. Hillebrand, W. F.; Lundell, G. E. F. Applied Inorganic Analysis, JohnWiley and Sons: New York, 1953.5. Van Loon, J. C. Analytical Atomic Absorption Spectroscopy.
AcademicPress: New York, 1980.6. Murray, R. W. Anal. Chem. 1991, 63, 271A.7. For several different viewpoints see (a) Beilby, A. L. J. Chem. Educ.1970, 47, 237–238; (b) Lucchesi, C. A. Am. Lab. 1980, October,113–119; (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) de Haseth, J.Spectroscopy 1990, 5, 20–21; (g) Strobel, H. A. Am. Lab. 1990,October, 17–24.8. Hieftje, G. M. Am. Lab. 1993, October, 53–61.9. See, for example, the following laboratory texts: (a) Sorum, C. H.;Lagowski, J. J. Introduction to Semimicro Qualitative Analysis, 5th ed.Prentice-Hall: Englewood Cliffs, NJ, 1977.; (b) Shriner, R.
L.; Fuson,R. C.; Curtin, D. Y. The Systematic Identification of OrganicCompounds, 5th ed. John Wiley and Sons: New York, 1964.1400-CH02 9/8/99 3:47 PM Page 11Chapter 2Basic Tools of Analytical ChemistryIn the chapters that follow we will learn about the specifics ofanalytical chemistry. In the process we will ask and answer questionssuch as “How do we treat experimental data?” “How do we ensure thatour results are accurate?” “How do we obtain a representativesample?” and “How do we select an appropriate analytical technique?”Before we look more closely at these and other questions, we will firstreview some basic numerical and experimental tools of importance toanalytical chemists.111400-CH02 9/8/99 3:47 PM Page 1212Modern Analytical Chemistry2A Numbers in Analytical ChemistryAnalytical chemistry is inherently a quantitative science.
Whether determining theconcentration of a species in a solution, evaluating an equilibrium constant, measuring a reaction rate, or drawing a correlation between a compound’s structureand its reactivity, analytical chemists make measurements and perform calculations.In this section we briefly review several important topics involving the use of numbers in analytical chemistry.2A.1 Fundamental Units of MeasureSI unitsStands for Système International d’Unités.These are the internationally agreed onunits for measurements.Imagine that you find the following instructions in a laboratory procedure: “Transfer 1.5 of your sample to a 100 volumetric flask, and dilute to volume.” How do youdo this? Clearly these instructions are incomplete since the units of measurementare not stated.
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