Analysis of Mixtures Subtract and Search Again

ANALYSIS OF MIXTURES SUBTRACT AND SEARCH AGAIN 

FIG U RE 3.31 The library search result for a mixture of cyclohexane and benzene. Note that cyclohexane is the best match (correlation algorithm, 0.0 is a perfect match). 

Unfortunately, there are some limitations to the subtract and search again method. In practice, it is usually only possible to identify the two or three most concentrated components in a given mixture. The problem is that every time a subtraction is performed, noise and artifacts are added to the result. After performing multiple subtractions using the same sample spectrum, the result will be so noisy and full of artifacts that the quality of the subsequent library search is poor as well, limiting the ability to identify more components. Despite this limitation, the subtract and search again technique is a useful way of dealing with the problem of mixture spectra. 

Krishnan and J. Ferraro, Chapter 5 in Fourier Transform Infrared Spectroscopy Techniques Using Fourier Transform Interferometry, K. Krishnan and L. Basile, Eds., Academic Press, San Diego, 1982. 

Peter Griffiths and James de Haseth, Fourier Transform Infrared Spectrometry 2nd Edition, Wiley, New York, 2007. 

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VIII. ANALYSIS OF MIXTURES SUBTRACT AND SEARCH AGAIN... 

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