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S. Radel, J. Schnöller, A. Dominguez-Vidal, B. Lendl, M. Gröschl, E. Benes:
"Ultrasonic particle manipulation approaches in on-line vibrational spectroscopy";
Vortrag: Eingeladener Vortrag, 19th Int. Congress on Acoustics - ICA, Madrid/E (eingeladen); 03.09.2007; in: "Proc. 19th Int. Congress on Acoustics, Eds., A. Calvo-Manzano, A. Pérez-López, S. Salvador", (2007), ISBN: 84-87985-12-2; Paper-Nr. CD-Rom Paper ULT-14-004, 6 S.

In this work an ultrasonic standing wave (USW) field of 2 MHz was used to manipulate particles
in different measurement cells for vibrational spectroscopy purposes.
These optical measurement techniques are increasingly popular in process analytical chemistry
because of their ability to directly provide molecular specific information about a given sample.
Especially in the regime of bioprocess control robust and reliable sensors with fast response
times are needed. A target is to discriminate between biological cells and the supernatant, i.e.
the suspending liquid during the measurement.
Employing the principles of ultrasonic particle manipulation we have developed a novel flow cell
for a horizontal attenuated total reflection (ATR) unit connected to a portable MIR-spectrometer.
Results show, that a decrease of the undesired formation of bio-films on the ATR surface (which
is unavoidable when using suspensions like fermentation broth) was achieved. In addition the
time resolution was increased.
Secondly an USW was used to manipulate yeast cells for assessment within the light path of a
confocal Raman microscope. Due to the increased spatial concentration of matter in the focus
of the laser beam an increase of the signal-to-noise ratio of the Raman spectra recorded from
the yeasts was established.