analvtical chemistry
March 1974, Vol. 46, NO.3 Editor: HERBERT A. LAITINEN
The Importance of Defining the Problem
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No phase of the analytical operation is more important than a precise statement of the problem t o be solved with the aid of analytical information. Because the problem usually originates outside of the analytical laboratory. it is crucial that ample communication exists to avoid costly and time-consuming effort that misses the mark. Perhaps a few examples will illustrate the point. Suppose t h a t an organic chemist desires to know the sulfhydryl content of a sample known to consist largely of mercaptan. An accurate RSH analysis may or may not give him the information he needs. All is well if he needs to know the number of sulfhydryl groups per unit weight. but if he really wants to know whether some of the mercaptan has been oxidized to di sulfide, then a direct determination of t h a t functional group would be in order, especially if there is anv ambiguity as to the molecular weight. Consider an ecologist who is interested in determining whether amplification of an environmental contaminant occurs up a food chain. Suppose that the first animal species in the food chain is an insect that feeds upon a plant and the second is a bird that feeds upon the insect. If the insect is a leaf-chem. ing species, the correct analysis of the plant would involve the unwashed leaves. However, if the insect is a sucking species, the correct analysis would involve the sap of the plant. In either case, the total insect would be analyzed to represent the diet of the bird. To take another environmental example. suppose that an engineer is interested in mapping the transport of a pollutant through a system of streams. He is not interested in whether the pollutant is truly in solution or carried with colloidal or suspended matter. In this case, the analyst may feel free to use any arbitrary separation of solution and solids, lust so long as both phases are properly analyzed. Quite a different situation exists, however, if a biologist desires to calculate a biological amplification factor for the concentration of pollutant in biological tissue as compared with its concentration in true solution. To the extent that the analytical chemist is brought into early and detailed consultation on a new problem, he can design the analvtical operation to procure the type of information most useful to the problem at hand.
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For submission of manuscripts, see page 268 A ANALYTICAL CHEMISTRY, VOL. 46, NO 3, MARCH 1974
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