Quantitative Analyses by IR Spectrometry

The quantitative determination of various compounds by mid-IR absorption is based on the measurement of the concentration of one of the functional groups of the analyte compound. For example, if we have a mixture of hexane and hexanol, the hexanol may be determined by measuring the intensity of absorption that takes place near 3300 cm by the OH band. The spectrum of pure hexanol would be used to determine the exact wavenumber corresponding to the absorption maximum. Alternatively, the intensity of absorption due to the C O at about 1100 cm could be used. From this, the concentration of alcohol can be calculated, once the intensity from a set of hexanol standards of known concentrations has been measured at the same wavenumber. Whenever possible, an absorption band unique to the sample molecule should be used for measuring purposes. 

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This reduces the problem of overlapping bands, although there are mathematical approaches for deconvoluting overlapping peaks. The quantitative calculation is based on Beer s law 

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