Química analítica

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 underlyingphysical 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 necessaryelements 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 1as 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 isoff-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 avoidabsurdities, 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 ofwhat 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 accuracyand 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 isreached. Apparatus is calibrated, relating its scales and markings to the appropriate physical standards. Solutions are standardized, relating the measured quantities to chemical behavior of knownmaterials. 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...