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T. Beskers, M. Brandstetter, J. Kuligowski, G. Quintas, M. Wilhelm, B. Lendl:
"High performance liquid chromatography with mid-infrared detection based on a broadly tunable quantum cascade laser";
Analyst, 139 (2014), 2057 - 2064.

This work introduces a tunable mid-infrared (mid-IR) external cavity quantum cascade laser (EC-QCL) as a
new molecular specific detector in liquid chromatography. An EC-QCL with a maximum tunability of
200 cm 1 (1030-1230 cm 1) was coupled to isocratic high performance liquid chromatography (HPLC)
for the separation of sugars with a cation exchange column (counter ion: Ca2+) and distilled water as the
mobile phase. Transmission measurements in a 165 mm thick flow cell allowed for on-line coupling and
independent quantification of glucose, fructose and sucrose in the concentration range from 5 mg mL 1
to 100 mg mL 1 in several beverages. The results obtained with the EC-QCL detector were found to be
in good agreement with those obtained using a differential refractive index detector as a reference. The
standard deviation of the method for the linear calibration was better than 5 mg mL 1 for all sugars and
reached a minimum of 1.9 mg mL 1, while the DRI detector reached a minimum of 1 mg mL 1. Besides
the quantification of sugars for which a calibration was performed, also chromatographic peaks of other
components could be identified on the basis of their IR absorption spectra. This includes taurine,
ethanol, and sorbitol.

http://dx.doi.org/10.1039/c3an01546g