Introducing the Analytical Perspective George F. Atkinson University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
I t is easy for a first course in analytical chemistry to focus on underlying physical chemistry, such as ionic equilibria or the origins of spectral phenomena, or on the details of the measurement experiments, titrimetric or gravimetric, while failing to set these necessary elements of the analytical chemist's stock of knowledge in the context of the overall analytical process. Attempting to overcome this problem, for several years I have used the scheme shown in Figure 1 as part of an introductory lecture. The stress is on analytical chemistry as an important component of a problem-solving process. The process begins with the discovery of a problem: the whisky is off-color, the piston rings are corroding, the customers will not buy the product. In search of a solution to the nrohlem. it is necessarv to formulate auestions. and seek answers. If we are to avoid absurdities, such as "Analyze the whisky," the analytical chemist needs to he involved at this question-making level to focus the questions. Once the questions to he answered are settled, the question of what to measure or observe in what sample by what method must be dealt with. In other words, an experiment must be designed. Generally, it is important to settle the question of the necessary accuracy and reproducibility, since this will influence both the appropriate level of care in sampling and the choice of a method. Finally, the part of the process most visible in the beginning laboratory is reached. Apparatus is calibrated, relating its scales and markings to the appropriate physical standards. Solutions are standardized, relating the measured quantities to chemical behavior of known materials. Measurements are made on the samples selected. The data resultine from the exneriment now becomes the focus of attention. First, it must he logged in its original form. Next, i t must be reduced, possibly by plotting points on a graph or by calculating measures of central tendency and of dispersion such as mean and standard deviation. The reduced data must he cross-checked to ensure that the accuracy and reproducibility sought have been attained. If not, the experience of doing the experiment should be brought to hear in deciding whether to acceut the discrepancy . . or to re-design - or re-perform the experime&. Once accepted, the data are carried into the answering of the questions formulated, and the answers in turn are applied to solving the original prohlem. In travelling around this U-shaped course, it should be stressed that the analytical chemist begins and ends dealing
of the U, in contrast, the chemist has retired to his lah and the others depend on his care, knowledge, and honesty. This general scheme from Figure 1is best related to one or more case histories from the lecturer's own experience, or carefully studied from the literature. The series, "The Analytical Approach" in Analytical Chem~strymay provide some useful starting points. Strategy of experimentation should he stressed. If a proposed approach can be rejected decisively on the outcome of an experiment, that one should be done first. If a question can be answered by an expelilnent giving a yesho or a more-thanlless-than result, it should be dealt with ahead of one requiring an accurate determination. The stress must lie with solving problems and getting answers to questions
EXPERIMENTS CALIBRATE STANDARDISE Figure 1. The Analytical Process.
R QUESTION
IDENTIFY-
-ESTIMATE
\.COST
Figure 2. Design of Analytical Experiment.
more than with accumulating numbers. It has been truly said, "Industry does analyses to stay in business. I t is not in business to do analyses." In developing this introduction, the scheme shown in Figure 2 may he useful to expand on what happens in the box marked Experimental Design. The problem is one of interrelating a question, a method and a sample. The sample may need to be identified (qualitative) or estimated (quantitative) wholly, or more likely with regard to one or more constituents. Alternatively, the chemical constitution of the sample may he quite irrelevant, hut it is necessary to characterize some property such as the color. Similarly, themethod corner of this triangle opens up the tradeoffs of speed, accuracy and cost. This introduction would soon he forgotten without reinforcement throughout the course, which often cornea from discussions of time and cost of various methods. Both elapsed time from sampling to results and working time in man-hours are considered. The latter hridges nicely to the consideration Volume 59
Number 3
March 1982
201
of labor costs as a prime tradeoff against capital equipment and running supplies and services costs of a method. The manner in which these considerations vary in importance depending on the frequency with which the analysis is needed can be illustrated in comparing the Volhard and gravimetric methods for chloride determination. Reference to suitable articles further reinforces the larger view. Despite its age, Lundell's "The Chemical Analysis of Things as They Are" ( I ) is excellent. Chalmers' "Chemistry as a Branch of Analytical Chemistryn (2) also deserves a place, as does Laitinen's "The Essence of Modern Analytical Chemistry" (3). These and many others are referred to in the
202
Journal of Chemical Education
course, and one or more are invoked in term paper topics. The integrative nature of analytical chemistry, combining general laws and principles with particularities uC Lhe reactions of specific chemicals in searching for a solution to a problem in the real world gives the subject a unique flavor and interest. The approach suggested helps to convey this uniqueness to students even in their first course in analytical chemistry. Literature Cited
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Lundell, G. B. F.. Ind. Enp. Chem.. Anal. Ed 5 . 221 (18331,alsa reprinted inMeinke, W. W . (Editai),Anolyliioi Chemi8lry:Kcy toPropres~onNatinnalPiublem, (N.B.S. Spec. Pub. 351) (1972). 12) Chs1rnem.K. A.andMarr.1.L.Z. Anal. Chem., 261,314 (1973). ( 3 ) Laitinen, H . A , A n d Chem.. 51,2065 (1879).
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