QUANTITATIVE INFRARED DETERMINATIONS IN MIXTURES OF UNKNOWN QUALITATIVE COMPOSITION
Creators:Cupples, Homer L.
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Publisher:Ohio State University
The basic rule that quantitative infrared determinations may only be made in systems of known qualitative composition is subject to well-known qualifications. The ""known qualitative composition"" may be replaced by a composition which is known not to interfere at selected wave lengths, or which produces a reproducible interference which may be handled by techniques employing ""blanks"" or ""base-line-density"" methods. Mixtures of truly unknown composition may introduce substantial inaccuracies into base-line-density methods. One possible solution is to select analytical wave lengths where the interference is least, with the objective of obtaining checks at several such wave lengths. A second approach, of a statistical nature, involves measurement of the component with a maximum number of base-line-density correlations, discarding results on a statistical basis, and averaging the remaining data. A valuable limiting value for a given component in a given mixture is obtained by referring the true absorbance of the mixture at selected wave lengths to the absorbance-concentration curve for that component. The lowest value so obtained is a limiting maximum value for the component.
Author Institution: Pesticide Chemicals Research Section,, U. S. Department of Agriculture
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