Concentrations of impurities in fluids often follow Zipf's law, that is, relatively few impurities occur at high concentrations and numerous impurities occur at low concentrations. The concentrations of compounds in air and of elements in ocean water are examples of such distributions. This principle can be used to predict the number of components in a mixture, which occur above certain concentration level, also beyond the range of analytical methods. In most practical applications the

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... of minor components can be ignored, but the level of concentration, at which certain component can be ignored depends on the specific problem.