SpectraProbe Linx 510

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SpectraProbe Linx 5-10
Process instrument
Lab instrument
MIR experiments featured a miniaturised
spectrometer attached to the end of a probe with
an ATR crystal the photograph features
laboratory and process versions of the
instrument.
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SpectraProbe Linx 5-10

• Probe and spectrometer integrated into a single
  unit
• Hastelloy probe with AMTIR crystal (ZnSe and Si
  crystals also available)
• 128 element pyro-electric array detector
• Chalcogenide fibres transport light to and from
  sample

The spectrometer has a dispersive optical system,
which allows coverage of 1000-2000 cm-1.
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Esterification of itaconic acid

• Reaction carried out in toluene
• Itaconic acid insoluble ? heterogeneous

The MIR probe was used to monitor a number of
processes including the esterification of
itaconic acid.
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Standard reaction

• 21 butanolitaconic acid
• 5 mL of catalyst (H2SO4)
• Oil jacket temperature 70 C
• Stir rate 250 rpm

The results that follow are for the conditions
shown (21 ratio of reagents).
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MIR spectra 1st derivative
C-C (toluene)
mono di
CO
C-O (mono di)
mono
During the course of the reaction features in the
first derivative spectrum increase or decrease as
indicated.
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Repeatability - MIR
Average RSD 3
When the same reaction was conducted on six
separate days and the change in the feature at
1769 cm-1 monitored, the average RSD was 3 this
is over a factor of two better than the
reproducibility of the HPLC method used to
monitor the reaction.
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Catalyst fault PCA of MIR spectra
By examining changes in the PC 1 score of the MIR
spectra, it is possible to identify if a reaction
is not proceeding as expected. In this example,
only 1 ml of catalyst was used initially the
fault could have been detected within a few
minutes of starting the reaction. After 30 min,
the additional amount of catalyst was added by
tracking the reaction using MIR spectrometry, the
additional time to reach the end point was easily
assessed.
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Quantitative analysis standard reactions
By building a chemometric model it was possible
to obtain reasonably good accuracy for
determination of the individual ester
concentrations.
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Summary - MIR

• Reproducibility of in-line MIR superior to HPLC
• Reasonable accuracy for prediction of standard
  reactions
• Average error of 5 for monoester gt 0.1 mol dm-3
• Average error of 8 for diester gt 0.02 mol dm-3
• Predictions poorer when reaction conditions
  changed, e.g. reagent ratio
• Can detect effects of low amount of catalyst
  using on-line MIR spectrometry and monitor effect
  of mitigating action taken to remedy problem