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I have a mixture of Ethanol / Methanol and Butanol that I wanted to assay. Would it be possible to develop a spectrophotometeric method for this? (Currently a GC is being used)

The analysis does not have to be too accurate. 1% accuracy would be fine. However the interest is in a rapid analysis and hence something like spectrophotometric is of interest.

Any thoughts?

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    $\begingroup$ I doubt that you could avoid chromatography. $\endgroup$
    – Poutnik
    Aug 26, 2023 at 5:29
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    $\begingroup$ Alkohols have no absorption spectrum in the visible region. In the UV region, their spectra are quite similar. So they are difficult to detect separately by UV spectrophotometry. $\endgroup$
    – Maurice
    Aug 26, 2023 at 10:03
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    $\begingroup$ And their chemistry is similar too, in case one would think about some more absorbing derivates. It would be slower with more effort and much less selectivity and accuracy than GC. $\endgroup$
    – Poutnik
    Aug 26, 2023 at 10:56
  • $\begingroup$ Thanks! A different question: any other sugesstions for a 3 component system that would be easy to analyse? This is for a distillation experiment so a non azeotropic system of miscible components is what I am looking for. $\endgroup$ Aug 27, 2023 at 4:15

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They have Significant differences in the C-H and C-O stretch areas that should resolve nicely at 2 or 1cm-1 resolution in a good FTIR. A multivariant analysis is necessary. I recommend a 3-bounce trough atr cell. This would give a constant pathlength and remain in the dynamic range of the instrument. Raman spectroscopy might also work same math; scan only the selected ranges.

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