[Zurück]

S. Lindner, J. Hayden, A. Schwaighofer, T. Wolflehner, C. Kristament, M. González-Cabrera, S. Zlabinger, B. Lendl:
"External Cavity Quantum Cascade Laser based Mid-Infrared Dispersion Spectroscopy for Qualitative and Quantitative Analysis of Liquid-Phase Samples";
Applied Spectroscopy, 74 (2020), 4; 23 S.

Acquisition of classical absorption spectra of liquids in the mid-IR range with quantum cascade lasers (QCLs) is often limited in sensitivity by noise from the laser source. Alternatively,
measurement of molecular dispersion (i.e. refractive index) spectra poses an experimental approach that
is immune to intensity fluctuations and further offers a direct relationship between the recorded signal and
the sample concentration. In this work, we present an EC-QCL based Mach-Zehnder interferometer setup
to determine dispersion spectra of liquid samples. We present two approaches for acquisition of refractive
index spectra and compare the qualitative experimental results. Furthermore, the performance for
quantitative analysis is evaluated. Finally, multivariate analysis of a spectrally complex mixture
comprising three different sugars is performed. The obtained figures of merit by partial least squares (PLS)
regression modelling compare well with standard absorption spectroscopy, demonstrating the potential of
the introduced dispersion spectroscopic method for quantitative chemical analysis.

http://dx.doi.org/10.1177/0003702819892646