Modern Analytical Chemistry 1. Identify the problem Determine type of information needed 5. Propose a solution ualitative, quantitative Conduct external evaluation characterization or fundamenta dentify context of the problem 2. Design the experimental procedure Establish design criteria (accuracy, precision scale of operation, sensitivity, selectivity, 4. Analyze the experimental dat cost, speed) Reduce or transform data dentify interferents Analyze statistics elect method Establish validation criteria Interpret results Establish sampling strategy Feedback 3. Conduct an experiment Calibrate instruments and equipment Standardize reagents Flow diagram for the analytical approach to Gather data lving problems; modified after Atkinson. analysis. Finding an appropriate balance between these parameters is frequently complicated by their interdependence. For example, improving the precision of an analysis may require a larger sample. Consideration is also given to collecting, stor ing, and preparing samples, and to whether chemical or physical interferences will affect the analysis. Finally, a good experimental procedure may still yield useless in formation if there is no method for validating the results. The most visible part of the analytical approach occurs in the laboratory. As part of the validation process, appropriate chemical or physical standards are used must be known. The selected samples are then analyzed and the raw data record i to calibrate any equipment being used and any solutions whose concentrations The raw data collected during the experiment are then analyzed. Frequently the ata must be reduced or transformed to a more readily analyzable form. A statistical treatment of the data is used to evaluate the accuracy and precision of the analysis and to validate the procedure. These results are compared with the criteria estab- lished during the design of the experiment, and then the design is reconsidered, ad- ditional experimental 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 re- sult in a new problem and the beginning of a new analytical cycle
Figure 1.3 Flow diagram for the analytical approach to solving problems; modified after Atkinson.7c analysis. Finding an appropriate balance between these parameters is frequently complicated by their interdependence. For example, improving the precision of an analysis may require a larger sample. Consideration is also given to collecting, storing, and preparing samples, and to whether chemical or physical interferences will affect the analysis. Finally, a good experimental procedure may still yield useless information if there is no method for validating the results. The most visible part of the analytical approach occurs in the laboratory. As part of the validation process, appropriate chemical or physical standards are used to calibrate any equipment being used and any solutions whose concentrations must be known. The selected samples are then analyzed and the raw data recorded. The raw data collected during the experiment are then analyzed. Frequently the data must be reduced or transformed to a more readily analyzable form. A statistical treatment of the data is used to evaluate the accuracy and precision of the analysis and to validate the procedure. These results are compared with the criteria established during the design of the experiment, and then the design is reconsidered, additional experimental 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 analytical cycle. 6 Modern Analytical Chemistry 1. Identify the problem Determine type of information needed (qualitative, quantitative, characterization, or fundamental) Identify context of the problem 2. Design the experimental procedure Establish design criteria (accuracy, precision, scale of operation, sensitivity, selectivity, cost, speed) Identify interferents Select method Establish validation criteria Establish sampling strategy Feedback loop 3. Conduct an experiment Calibrate instruments and equipment Standardize reagents Gather data 4. Analyze the experimental data Reduce or transform data Analyze statistics Verify results Interpret results 5. Propose a solution Conduct external evaluation 1400-CH01 9/9/99 2:20 PM Page 6
Chapter 1 Introduction As an exercise, let,s adapt this model of the analytical approach to a real prob- lem. For our example, we will use the determination of the sources of airborne pol- lutant particles. A description of the problem can be found in the following article Tracing Aerosol Pollutants with Rare Earth Isotopes"by Ondov, J. M. Kelly, w.R. Anal. Chem. 1991, 63, 691A-697A Before continuing, take some time to read the article, locating the discussions per taining to each of the five steps outlined in Figure 1.3. In addition, consider the fol lowing questions: 1. What is the analytical problem 2. What type of information is needed to solve the problem? 3. How will the solution to this problem be used? 4. What criteria were considered in designing the experimental procedure? 5. Were there any potential interferences that had to be eliminated? If so, how were they treated? 6. Is there a plan for validating the experimental method? 7. How were the samples collected? 8. Is there evidence that steps 2, 3, and 4 of the analytical approach are repeat more than once? According to our model, the analytical approach begins with a problem. The motivation for this research was to develop a method for monitoring the transport of solid aerosol particulates following their release from a high-temperature com- bustion source. Because these particulates contain significant concentrations of toxic heavy metals and carcinogenic organic compounds, they represent a signifi cant environmental hazard An aerosol is a suspension of either a solid or a liquid in a gas. Fog, for exam- pIe, is a suspension of small liquid water droplets in air, and smoke is a suspension of small solid particulates in combustion gases. In both cases the liquid or solid pai ticulates must be small enough to remain suspended in the gas for an extended time. Solid aerosol particulates, which are the focus of this problem, usually have micrometer or submicrometer diameters. Over time, solid particulates settle out from the gas, falling to the Earths surface as dry deposition. Existing methods for monitoring the transport of gases were inadequate for studying aerosols. To solve the problem, qualitative and quantitative information were needed to determine the sources of pollutants and their net contribution to the total dry deposition at a given location. Eventually the methods developed in this study could be used to evaluate models that estimate the contributions of point sources of pollution to the level of pollution at designated locations Following the movement of airborne pollutants requires a natural or artificial tracer(a species specific to the source of the airborne pollutants )that can be exper mentally measured at sites distant from the source. Limitations placed on the tracer,therefore, governed the design of the experimental procedure. These limita- tions included cost, the need to detect small quantities of the tracer, and the ab- sence of the tracer from other natural sources. In addition aerosols are emitted from high-temperature combustion sources that produce an abundance of very re- active species. The tracer, therefore, had to be both thermally and chemically stable On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method(thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of
As an exercise, let’s adapt this model of the analytical approach to a real problem. For our example, we will use the determination of the sources of airborne pollutant particles. A description of the problem can be found in the following article: “Tracing Aerosol Pollutants with Rare Earth Isotopes” by Ondov, J. M.; Kelly, W. R. Anal. Chem. 1991, 63, 691A–697A. Before continuing, take some time to read the article, locating the discussions pertaining to each of the five steps outlined in Figure 1.3. In addition, consider the following questions: 1. What is the analytical problem? 2. What type of information is needed to solve the problem? 3. How will the solution to this problem be used? 4. What criteria were considered in designing the experimental procedure? 5. Were there any potential interferences that had to be eliminated? If so, how were they treated? 6. Is there a plan for validating the experimental method? 7. How were the samples collected? 8. Is there evidence that steps 2, 3, and 4 of the analytical approach are repeated more than once? 9. Was there a successful conclusion to the problem? According to our model, the analytical approach begins with a problem. The motivation for this research was to develop a method for monitoring the transport of solid aerosol particulates following their release from a high-temperature combustion source. Because these particulates contain significant concentrations of toxic heavy metals and carcinogenic organic compounds, they represent a significant environmental hazard. An aerosol is a suspension of either a solid or a liquid in a gas. Fog, for example, is a suspension of small liquid water droplets in air, and smoke is a suspension of small solid particulates in combustion gases. In both cases the liquid or solid particulates must be small enough to remain suspended in the gas for an extended time. Solid aerosol particulates, which are the focus of this problem, usually have micrometer or submicrometer diameters. Over time, solid particulates settle out from the gas, falling to the Earth’s surface as dry deposition. Existing methods for monitoring the transport of gases were inadequate for studying aerosols. To solve the problem, qualitative and quantitative information were needed to determine the sources of pollutants and their net contribution to the total dry deposition at a given location. Eventually the methods developed in this study could be used to evaluate models that estimate the contributions of point sources of pollution to the level of pollution at designated locations. Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of Chapter 1 Introduction 7 1400-CH01 9/9/99 2:20 PM Page 7
Modern Analytical Chemistry Nd in samples. Unfortunately, mass spectrometry is not a selective technique. A mass spectrum provides information about the abundance of ions with a given mass. It cannot distinguish, however, between different ions with the same mass. Consequently, the choice of TIMS required developing a procedure for separating the tracer from the aerosol particulates Validating the final experimental protocol was accomplished by running a model study in which 4Nd was released into the atmosphere from a 100-MW coal utility boiler. Samples were collected at 13 locations, all of which were 20 km from the source. Experimental results were compared with predictions determined by the rate at which the tracer was released and the known dispersion of the emissions Finally, the development of this procedure did not occur in a single, linear pass through the analytical approach. As research progressed, problems were encoun Others have pointed out, with justification, that the analytical approach out- lined here is not unique to analytical chemistry, but is common to any aspect of sci- ence involving analysis. Here, again, it helps to distinguish between a chemical analysis and analytical chemistry. For other analytically oriented scientists, such as physical chemists and physical organic chemists, the primary emphasis is on the problem, with the results of an analysis supporting larger research goals involving fundamental studies of chemical or physical processes. The essence of analytical chemistry, however, is in the second, third, and fourth steps of the analytical ap proach. Besides supporting broader research goals by developing and validating an- alytical methods, these methods also define the type and quality of information available to other research scientists. In some cases, the success of an analytical method may even suggest new research problems. Common Analytical Problems In Section lA we indicated that analytical chemistry is more than a collection of qualitative and quantitative methods of analysis. Nevertheless, many problems on which analytical chemists work ultimately involve either a qualitative or quantita- tive measurement. Other problems may involve characterizing a sample's chemical or physical properties. Finally, many analytical chemists engage in fundamental studies of analytical methods. In this section we briefly discuss each of these four areas of analysis. Many problems in analytical chemistry begin with the need to identify what present in a sample. This is the scope of a qualitative analysis, examples of which An an which we determine the clude identifying the products of a chemical reaction, screening an athlete dentity of the constituent species in a for the presence of a performance-enhancing drug, or determining the spatial dis tribution of Pb on the surface of an airborne particulate. Much of the early work in analytical chemistry involved the development of simple chemical tests to identify the presence of inorganic ions and organic functional groups. The classical labora- tory courses in inorganic and organic qualitative analysis, still taught at some schools, are based on this work. Currently, most qualitative analyses use methods such as infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry. These qualitative applications of identifying organic and inorganic compounds are covered adequately elsewhere in the undergraduate curriculum and, so, will receive no further consideration in this text
8 Modern Analytical Chemistry qualitative analysis An analysis in which we determine the identity of the constituent species in a sample. Nd in samples. Unfortunately, mass spectrometry is not a selective technique. A mass spectrum provides information about the abundance of ions with a given mass. It cannot distinguish, however, between different ions with the same mass. Consequently, the choice of TIMS required developing a procedure for separating the tracer from the aerosol particulates. Validating the final experimental protocol was accomplished by running a model study in which 148Nd was released into the atmosphere from a 100-MW coal utility boiler. Samples were collected at 13 locations, all of which were 20 km from the source. Experimental results were compared with predictions determined by the rate at which the tracer was released and the known dispersion of the emissions. Finally, the development of this procedure did not occur in a single, linear pass through the analytical approach. As research progressed, problems were encountered and modifications made, representing a cycle through steps 2, 3, and 4 of the analytical approach. Others have pointed out, with justification, that the analytical approach outlined here is not unique to analytical chemistry, but is common to any aspect of science involving analysis.8 Here, again, it helps to distinguish between a chemical analysis and analytical chemistry. For other analytically oriented scientists, such as physical chemists and physical organic chemists, the primary emphasis is on the problem, with the results of an analysis supporting larger research goals involving fundamental studies of chemical or physical processes. The essence of analytical chemistry, however, is in the second, third, and fourth steps of the analytical approach. Besides supporting broader research goals by developing and validating analytical methods, these methods also define the type and quality of information available to other research scientists. In some cases, the success of an analytical method may even suggest new research problems. 1C Common Analytical Problems In Section 1A we indicated that analytical chemistry is more than a collection of qualitative and quantitative methods of analysis. Nevertheless, many problems on which analytical chemists work ultimately involve either a qualitative or quantitative measurement. Other problems may involve characterizing a sample’s chemical or physical properties. Finally, many analytical chemists engage in fundamental studies of analytical methods. In this section we briefly discuss each of these four areas of analysis. 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, screening an athlete’s urine for 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 in analytical chemistry involved the development of simple chemical tests to identify the presence of inorganic ions and organic functional groups. The classical laboratory courses in inorganic and organic qualitative analysis,9 still taught at some schools, are based on this work. Currently, most qualitative analyses use methods such as infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry. These qualitative applications of identifying organic and inorganic compounds are covered adequately elsewhere in the undergraduate curriculum and, so, will receive no further consideration in this text. 1400-CH01 9/9/99 2:20 PM Page 8
Chapter 1 Introduction Perhaps the most common type of problem encountered in the analytical lab is a quantitative analysis. Examples of typical quantitative analyses include the ele- quantitative analysis mental analysis of a newly synthesized compound, measuring the concentration of An analysis in which we determine how glucose in blood, or determining the difference between the bulk and surface con much of a constituent species is present centrations of Cr in steel. Much of the analytical work in clinical, pharmaceutical, environmental, and industrial labs involves developing new methods for determin g the concentration of targeted species in complex samples. Most of the example in this text come from the area of quantitative analysis Another important area of analytical chemistry, which receives some attention this text, is the development of new methods for characterizing physical and chemical 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 to An analysis in which we evaluate a solve a problem associated with a sample. A fundamental analysis, on the other sample's chemical or physical properties. hand, is directed toward improving the experimental methods used in the other areas of analytical chemistry Extending and improving the theory on which a fundamental analysis method is based, studying a method's limitations, and designing new and modify nalytical methods capabilities. ing old methods are examples of fundamental studies in analytical chemistry ID KEY TERMS characterization analysis (p. 9) qualitative analysis (p. 8) quantitative analysis (P. 9) IE SUMMARY Analytical chemists work to improve the ability of all chemists to chemists to improve existing analytical methods and to develop make meaningful measurements. Chemists working in medicina ew analytical techniques. chemistry, clinical chemistry, forensic chemistry, and environ Typical problems on which analytical chemists work include mental chemistry, as well as the more traditional of chem qualitative analyses(what is present?), quantitative analyses istry, need better tools for analyzing materials. The need to work (how much is present?), characterization analyses(what are with smaller quantities of material, with more complex materi the material' s chemical and physical properties and funda als, with processes occurring on shorter time scales, and with mental analyses(how does this method work and how can it be species present at lower concentrations challenges analytical IF PROBLEMS 1. For each of the following problems indicate whether its d. The structure of a newly discovered virus needs to be solution requires a qualitative, quantitative, characterization, determined or fundamental study. More than one type of analysis may be e. A new visual indicator is needed for an acid-base titration appropriate for some problems. f. A new law requires a method for evaluating whether a. A hazardous-waste disposal site is believed to be leaking automobiles are emitting too much carbon monoxide. contaminants into the local groundwater. 2. Read a recent article from the column"Analytical Approach, b. An art museum is concerned that a recent acquisition is a published in Analytical Chemistry, or an article assigned by your instructor, and write an essay summarizing the nature of c. A more reliable method is needed by airport security for the problem and how it was solved. As a guide, refer back to detecting the presence of explosive materials in luggage Figure 1.3 for one model of the analytical approach
Perhaps the most common type of problem encountered in the analytical lab is a quantitative analysis. Examples of typical quantitative analyses include the elemental analysis of a newly synthesized compound, measuring the concentration of glucose 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 examples in this text come from the area of quantitative analysis. Another important area of analytical chemistry, which receives some attention in this text, is the development of new methods for characterizing physical and chemical 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 to solve a problem associated with a sample. A fundamental analysis, on the other hand, is directed toward improving the experimental methods used in the other areas of analytical chemistry. Extending and improving the theory on which a method is based, studying a method’s limitations, and designing new and modifying old methods are examples of fundamental studies in analytical chemistry. Chapter 1 Introduction 9 characterization analysis An analysis in which we evaluate a sample’s chemical or physical properties. fundamental analysis An analysis whose purpose is to improve an analytical method’s capabilities. quantitative analysis An analysis in which we determine how much of a constituent species is present in a sample. 1D KEY TERMS characterization analysis (p. 9) fundamental analysis (p. 9) qualitative analysis (p. 8) quantitative analysis (p. 9) Analytical chemists work to improve the ability of all chemists to make meaningful measurements. Chemists working in medicinal chemistry, 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 work with smaller quantities of material, with more complex materials, with processes occurring on shorter time scales, and with species present at lower concentrations challenges analytical chemists to improve existing analytical methods and to develop new analytical techniques. Typical problems on which analytical chemists work include qualitative analyses (what is present?), quantitative analyses (how much is present?), characterization analyses (what are the material’s chemical and physical properties?), and fundamental analyses (how does this method work and how can it be improved?). 1E SUMMARY 1. For each of the following problems indicate whether its solution requires a qualitative, quantitative, characterization, or fundamental study. More than one type of analysis may be appropriate for some problems. a. A hazardous-waste disposal site is believed to be leaking contaminants into the local groundwater. b. An art museum is concerned that a recent acquisition is a forgery. c. A more reliable method is needed by airport security 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 a recent article from the column “Analytical Approach,” published in Analytical Chemistry, or an article assigned by your instructor, and write an essay summarizing the nature of the problem and how it was solved. As a guide, refer back to Figure 1.3 for one model of the analytical approach. 1F PROBLEMS 1400-CH01 9/9/99 2:20 PM Page 9
Modern ana IG SUGGESTED READINGS The role of analytical chemistry within the broader discipline of Mottola, H. A. The Interdisciplinary and Multidisciplinary hemistry has been discussed by many prominent analytical Nature of Contemporary Analytical Chemistry and Its Core chemists. Several notable examples follow Components, "Anal. Chim. Acta 1991, 242, 1-3. Baiulescu. g. E: Patroescu, C. ChalmersR.A. Education and Tyson, J. Analysis: What Analytical Chemists Do. Royal Society of Teaching in Analytical Chemistry. Ellis Horwood: Chichester, Cambridge, England, 1988. Several journals are dedicated to publishing broadly in the Hieftje, G. M. The Two Sides of Analytical Chemistry, Anal. field of analytical chemistry, including Analytical Chemistry, Chem.1985,57,256A-267A. Analytica Chimica Acta, Analyst, and Talanta. Other journals, too Kissinger,P.T"Analytical Chemistry-What is It? Who Needs It? numerous to list, are dedicated to single areas of analytical Why Teach It? " Trends Anal. Chem. 1992, 11, 54-57. emistry aitinen, H.A. Analytical Chemistry in a Changing World, Current research in the areas of quantitative analysis, qualitative Anal.Chem1980,52,605A-609A analysis, and characterization analysis are reviewed biannually Laitinen, H. A. History of Analytical Chemistry in the U.S.A., dd-numbered years )in Analytical Chemistry's"Application Talanta1989,36,1-9 Reviews.” Laitinen, H. A; Ewing, G(eds).A Current research on fundamental developments in analytical Chemistry. The Division of Analytical Chemistry of the hemistry are reviewed biannually(even-numbered years)in American Chemical Society: Washington, D.C., 1972. Analytical Chemistry's"Fundamental Reviews. McLafferty, F W. Analytical Chemistry: Historic and Modern, Acc Chen.Re.1990,23,63-64 H REFERENCES 1. Ravey, M. Spectroscopy 1990, 5(7), 11 113-119;(c) Atkinson,G.F.J.ahem.htc1982,59,201-202; de Haseth, J Spectroscopy 1990, 5(7),11 (d) Pardue, H. L: Woo, J. Che. Educ. 1984, 61, 409-412 3. Fresenius, C.R. A System of Instruction in Quantitative Chemical e)Guarnieri, M. Chem. Educ. 1988, 65, 201-203;(fde Haseth, I. Analysis. John Wiley and Sons: New York, 1881 py 1990, 5, 20-21;(g) Strobel, H. A Am. Lab. 1990, 4. Hillebrand, w. F; Lundell, G. E. F Applied Inorganic Analysis, John October 17-24 Wiley and Sons: New York, 1953. 8. Hieftje, G. M. Am. Lab. 1993, October, 53-61 5. Van Loon, J CAr Atomic Absorption Spectroscopy. Academic 9. See, for example, the ing laboratory texts: (a)Soru Press: New York,, 1980 Lagowski, JJ. Introduction to Semimicro Qualitative Analysis, 5th ed. 6. Murray, R. w. Anal. Chem. 1991, 63, 271A. Prentice-Hall: Englewood Cliffs, N, 1977;(b)Shriner, R L; Fuson, R. C; Curtin, D. Y. The Systematic Identification of organic 7. For several different viewpoints see(a)Beilby, A. L.J. Chem. Educ. Compounds, 5th ed. John Wiley and Sons: New York, 1964. 1970, 47, 237-238;(b)Lucchesi, C. A. Am. Lab. 1980, October
10 Modern Analytical Chemistry The role of analytical chemistry within the broader discipline of chemistry has been discussed by many prominent analytical chemists. Several notable examples follow. Baiulescu, G. E.; Patroescu, C.; Chalmers, R. A. Education and Teaching 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 Analytical Chemistry. The Division of Analytical Chemistry of the American 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 Multidisciplinary Nature of Contemporary Analytical Chemistry and Its Core Components,” Anal. Chim. Acta 1991, 242, 1–3. Tyson, J. Analysis: What Analytical Chemists Do. Royal Society of Chemistry: Cambridge, England, 1988. Several journals are dedicated to publishing broadly in the field of analytical chemistry, including Analytical Chemistry, Analytica Chimica Acta, Analyst, and Talanta. Other journals, too numerous to list, are dedicated to single areas of analytical chemistry. Current research in the areas of quantitative analysis, qualitative analysis, and characterization analysis are reviewed biannually (odd-numbered years) in Analytical Chemistry’s “Application Reviews.” Current research on fundamental developments in analytical chemistry are reviewed biannually (even-numbered years) in Analytical Chemistry’s “Fundamental Reviews.” 1G SUGGESTED READINGS 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. 4. Hillebrand, W. F.; Lundell, G. E. F. Applied Inorganic Analysis, John Wiley and Sons: New York, 1953. 5. Van Loon, J. C. Analytical Atomic Absorption Spectroscopy. Academic Press: 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 Organic Compounds, 5th ed. John Wiley and Sons: New York, 1964. 1H REFERENCES 1400-CH01 9/9/99 2:20 PM Page 10