Highly Sensitive Raman Spectroscopy with Low Laser Power for Fast In-Line Reaction and Multiphase Flow Monitoring.
In process analytics, the applicability of Raman spectroscopy is restricted by high excitation intensities or the long integration times required. In this work, a novel Raman system was developed to minimize photon flux losses. It allows specific reduction of spectral resolution to enable the use of Raman spectroscopy for real-time analytics when strongly increased sensitivity is required. The performance potential of the optical setup was demonstrated in two exemplary applications: First, a fast exothermic reaction (Michael addition) was monitored with backscattering fiber optics under strongly attenuated laser power (7 mW). Second, high-speed scanning of a segmented multiphase flow (water/toluene) with submicroliter droplets was achieved by aligning the focus of a coaxial Raman probe with long focal length directly into a perfluoroalkoxy (PFA) capillary. With an acquisition rate of 333 Raman spectra per second, chemical information was obtained separately for both of the rapidly alternating phases. The experiment with reduced laser power demonstrates that the technique described in this paper is applicable in chemical production processes, especially in hazardous environments. Further potential uses can be envisioned in medical or biological applications with limited power input. The realization of high-speed measurements shows new possibilities for analysis of heterogeneous phase systems and of fast reactions or processes.
Mannheim University of Applied Sciences , Institute of Process Control and Innovative Energy Conversion, Paul-Wittsack-Str. 10, 68163 Mannheim, Germany.
Frank
F
Braun
Mannheim University of Applied Sciences , Institute of Chemical Process Engineering, Paul-Wittsack-Str. 10, 68163 Mannheim, Germany.
Sebastian
S
Schwolow
Mannheim University of Applied Sciences , Institute of Process Control and Innovative Energy Conversion, Paul-Wittsack-Str. 10, 68163 Mannheim, Germany.
Julia
J
Seltenreich
TU Dortmund University , Biochemical and Chemical Engineering, Equipment Design, Emil-Figge-Straße 68, 44227 Dortmund, Germany.
Norbert
N
Kockmann
Mannheim University of Applied Sciences , Institute of Chemical Process Engineering, Paul-Wittsack-Str. 10, 68163 Mannheim, Germany.
Thorsten
T
Röder
Medical Research Center, Medical Faculty Mannheim, University of Heidelberg , Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany.
Norbert
N
Gretz
Mannheim University of Applied Sciences , Institute of Process Control and Innovative Energy Conversion, Paul-Wittsack-Str. 10, 68163 Mannheim, Germany.
Matthias
M
Rädle