Use of a novel mid-infrared spectrometer for quantitative in situ

analysis of liquids

Authors: Catriona McFarlan1, Jaclyn Dunn1, and Alison Nordon1

1WestCHEM, Department of Pure and Applied Chemistry and CPACT, University of Strathclyde, Glasgow, UK

www.strath.ac.uk/science/chemistry/Jolyon Tidmarsh2 and Dan Wood2

2 Keit Ltd., Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK

www.keit.co.uk

APACT 2016 Poster Presentation20-22 April 2016, Chester, UK

Introduction• Optical spectroscopy is extremely useful in process monitoring

and control as it is rapid, does not require sampling, and is able to provide continuous information in real-time.

• Mid-infrared spectroscopy has significant advantages over other types of optical spectroscopy such as near-infrared, as it is more sensitive and produces spectra with distinct peaks and greater definition.

• However mid-infrared light is not easily transmiBed through optical fibres, and transmission is generally only possible over short lengths of optical fibre.

• In this work the performance of a novel mid-infrared spectrometer with a probe directly aBached is assessed for in situ analysis of liquids.

Performance Assessment

• Sixteen calibration samples were prepared, containing acetone, ethanol and ethyl acetate in the ratios, along with six test samples as shown in Figure 3.

• Each sample was analysed using the Keit spectrometer. The spectra of the pure acetone, ethanol and ethyl acetate samples are shown in Figure 4.

• It was possible to predict the concentrations of acetone, ethyl acetate and ethanol with an average error of less than 3%.

• The novel spectrometer design opens up new opportunities for in situ process monitoring in the mid-infrared region.

Use of a novel mid-infrared spectrometer for quantitative in situ analysis of liquids

Catriona McFarlan1, Jaclyn Dunn1, Alison Nordon1, Jolyon Tidmarsh2 and Dan Wood2

1 WestCHEM, Department of Pure and Applied Chemistry and CPACT, University of Strathclyde, Glasgow, UK2 Keit Ltd., Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, UK

The Keit Spectrometer

• The Keit spectrometer is a compact mid-infrared spectrometer with a probe directly aBached as shown in Figure 1, eliminating the need for long lengths of fibre optics.

• Instead of the Michelson interferometer design, which involves the use of delicate moving parts, the Keit spectrometer utilises a novel design of interferometer shown in Figure 2.

• The novel interferometer does not involve moving parts, so is extremely robust, and eliminates spectral noise.

• The spectrometer covers the region 800 – 2000 cm-1 with aresolution of 16 cm-1 and the data have been interpolated to give a data point approximately every 1.5 cm-1.

Figure 1 – The Keit spectrometer

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Figure 4 – Spectra of pure acetone, ethanol and ethyl acetate obtained using the Keit spectrometer

Figure 5 – Predicted versus actual concentratins of acetone, ethanol and ethyl acetate

Conclusion

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• Individual partial least squares (PLS1) models were built using the calibration spectra, and used to predict the concentration of each solvent present in the test samples.

• The concentrations of each solvent predicted using PLS1 are ploBed against the actual concentrations in Figure 5.

Figure 2 – The Keit interferometer

Acknowledgements

Thanks to EPSRC and CPACT for providing funding.

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Figure 3 – Composition of calibration samples (black) and test samples (red)

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Use of a novel mid-infrared spectrometer for quantitative in situ

analysis of liquids

Authors: Catriona McFarlan1, Jaclyn Dunn1, and Alison Nordon1

1WestCHEM, Department of Pure and Applied Chemistry and CPACT, University of Strathclyde, Glasgow, UK

www.strath.ac.uk/science/chemistry/Jolyon Tidmarsh2 and Dan Wood2

2 Keit Ltd., Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK

www.keit.co.uk

APACT 2016 Poster Presentation20-22 April 2016, Chester, UK