In-line monitoring of esterification using a miniaturised mid-Infrared spectrometer

D. Littlejohn, C.A. McGill, R.H. Ferguson, A. Nordon, K.G. Donoghue

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


A miniaturised mid-infrared (MIR) spectrometer attached directly to an in-line immersion probe with an attenuated total reflectance crystal has been used to monitor the progression of the batch reaction of crotonic acid and 2-butanol in toluene. Univariate calibration, using the signal at 1188 cm−1 in the 2nd derivative spectrum, gave accurate (average error, 1.6%) and precise (average relative standard deviation, 5.2%) estimation of 2-butyl crotonate concentrations in the range 0.08–0.49 mol dm−3. Calibration by partial least squares was of no additional benefit in this application. The performance of in-line MIR spectrometry was comparable to that of an off-line reference gas chromatography method and superior to that of other in-line process analysis techniques (near-infrared, Raman or UV-visible spectrometries).
Original languageEnglish
Pages (from-to)1467-1470
Number of pages4
Publication statusPublished - 2003


  • Infrared spectrometer
  • esterification

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