Unifying Approach to Analytical Chemistry and Chemical Analysis Problem-Oriented Role of Chemical Analysis Harry L. Pardue Department of Chemistry, Purdue University, West Lafayette, IN 47907 Jannie Woo Department of Pathology, SUNY Upstate Medical Center, Syracuse, NY 13012 This paper introducrs a proposal for a unifying appronch tu the teachinr! of analvtical chemistrv and rhcmicnl analvsis. The proposalk basedVonthe conviciion that there is a more systematic pattern to the discipline than is reflected in currently available texts on the subject. We believe that the discipline of analytical chemistry can be represented accurately a s several hierarchical levels of functional processes and operational approaches that are integrated to help resolve problems with the aid of qualitative and quantitative chemical information. Although current texts are quite effective in the presentation of the fundamental and applied aspects of operational approaches, they are less effective in developing clear distinction'among the functional processes and interrelationships among the different operational approaches. This paper deals only with functional processes, with primary emphasis on a problem-oriented role of chemical analysis. Figure 1 presents a three-level hierarchy of functional processes in analytical chemistry. The words chemical analysis, determination, and measurement are highlighted in the figure because they tend to be used more or less interchangeahlv in analvtical texts. In the . ~roposed hierarchv, . chemical analysis is one of four major components that make UD the discipline of analvtical chemistrv, .. a determination is just one of several necessary steps in an analysis, and a measurement is one of several possible steps in a determination. While it is expected that some aspects of the proposal are consistent with traditional views, i t is recognized that the problem-oriented role of chemical analysis is not, and that is the primary subject of this paper. 'the trilditioni~view of chemical analysis is a process that is used to dtwrmine the cumposition uf matter. There are some who believe that this view of analysis is outdated and misleading. Laitinen (I)stated that "Fifty years ago, the only
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question analysts sought to answer was the composition of matter . . ." and suggested that "Analysis can now he more accurately described as being applied to a problem rather than t o a sample." Siggia ( 2 )stated that ". . . chemical analysis is not concerned with merely detecting or determining a specific component or the general composition of a sample. I t is the resolution or elucidation of a situation." Others have expressed similar views ( 3 , 4 ) . The principal focus of the problem-oriented role of chemical analysis described by Figure 1is the problem to he resolved rather than some sample related to it. The most compelling reason that this problem-oriented role of analysis should be an integral part of analytical courses is that useful information will seldom be obtained unless sample-oriented operations are based on adequate advance planning related to what data are needed and how the data will he interpreted. Whereas the more traditional, sample-oriented view of analysis leads clients to expect that useful information will be obtained simply by submitting samples, the problem-oriented approach should demonstrate that problem-related dialogue is an indispensable part of clientlanalyst interactions. While it is essential that our texts and courses continue to present the fundamental and applied aspects of sample-oriented processes, it is equally important that these dicussions be presented in the context of real problems that keep qualitative and quantitative determinations in perspective with the thought processes that always precede and follow them in real situations. A typical problem is discussed below to illustrate some more detailed aspects of this proposal. The example (5) involves a medical diagnosis for a middle-aged woman admitted to a hospital in shock with a history of chest pains. Because electrocardiographic abnormalities suggested but did not confirm a tentative diagnosis of heart
Volume 61 Number 5 May 1984
409
ANALYTICAL CHEMISTRY
Clinical Data Electrocardiogram AST, ALT, Amylase
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Suspect Heart Damage
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Suspect Pancreatitis
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Diagnosis Confirmed
Figure 1. Overview of the major functionalprocesses in analytical chemistry.
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Figure 3. Cyclic process involved in the diagnosis of patient data.
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Figure 2. Daily patterns of serum enzymes for a patient (-) and for confirmed cases of myocardial infarction(- - -). Reprinted with permission (5). attack (mvocardial infarction). . . serum activities of two en. . zymes, aspartate amino transf~rase(AST) and alanine amino transferase IA1.T).. . were auantified to test the tentative diagnosis. Figure 2 shows the patient results along with typical 410
Journal of Chemical Education
resulu for a person with r o d ~ r m e dmyocardial infarrtion. The arossly elevated valuesof both AS'I'and ALTon the first day nullified the initial diagnosis, and led to a second tentative diagnosis of ~ancreatitis.This second diagnosis was tested with amylaseartivity. The rlevared value of amylase on the second day alonr with other clinical data confirmed a diagnosis of acute paicreatitis (5). Figure 3 is a graphic illustration of how chemical data were used in the resolution of this process. The cyclic process illustrated for this specific problem can be generalized to apply to most problems in which chemical data are useful in their
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