Process Raman Spectroscopy

Raman spectroscopy is based on a physical effect caused by inelastic scattering. For a portion of the scattered light, the photons energy is changed resulting in a wavelength shift. This wavelength shift is characteristic for the molecule and this effect underscores the strong selectivity; both qualitative and quantitative analysis can be carried out.
Over the past years, Raman spectroscopy was mostly used for the analysis in laboratory and only a small number of applications in process analytic control.
Compared to the widely used NIR spectroscopy it has major advantages as the selectivity is higher and more complex mixtures can be analysed. In addition, water does not influence the spectrum strongly. The high availability of fiber-optic components based on fused silica allows a distributed installation online - with a single instrument having multiple measurement points.

MultiSpec Raman Spektrometer System tec5

Applications of our customers realized with Raman spectroscopy:

Monitoring of Biocatalytic Synthesis of Naproxen by Raman Spectroscopy
Biological transformations are increasingly used in the production of fine chemicals or pharmaceutical ingredients. Process monitoring following the synthesis of Naproxen in a biocatalytic synthesis was demonstrated within this poster and published in the following paper.
Non-contact Raman spectroscopy for in-line monitoring of glucose and ethanol during yeast fermentations
 
The monitoring of microbiological processes using Raman spectroscopy has gained in importance over the past few years. Commercial Raman spectroscopic equipment consists of a laser, spectrometer, and fiberoptic immersion probe in direct contact with the fermentation medium. To avoid possible sterilization problems and biofilm formation on the probe tip, a large-aperture Raman probe was developed. The design of the probe enables non-contact in-line measurements through glass vessels or inspection glasses of bioreactors and chemical reactors. The practical applicability of the probe was tested during yeast fermentations by monitoring the consumption of substrate glucose and the formation of ethanol as the product. Multiple linear regression models were applied to evaluate the Raman spectra. Reference values were determined by high-performance liquid chromatography. The relative errors of prediction for glucose and ethanol were 5 and 3%, respectively. The presented Raman probe allows simple adaption to a wide range of processes in the chemical, pharmaceutical, and biotechnological industries.
 
Non invasive process probe for inline Raman monitoring through optical inspection glasses

Raman spectroscopy features some significant advantages against existing spectroscopic techniques. Amongst them are higher chemical sensitivities compared to NIR and a relatively low detection range for water molecules, in contrast to MIR spectroscopy. In process installations, compared to all spectroscopic techniques Raman plays only a minor role. Main challenges for process integration are long-term stability of the available measurement systems, high installation costs of so-called immersion probes and the addition of measurement points to existing plant layouts in piping and vessels.Read the complete abstract in the following link.
 

Non-Invasive Raman Reaction-Monitoring in Microchannels 

In-line Raman spectroscopy is an efficient tool for investigating kinetics of chemical reactions or for monitoring analyte concentrations nearly in real time. Compared to off-line product analysis like HPLC or GC, no quenching or further sample preparation is required. Both posters describe the use of a MultiSpec® Raman system for kinetic studies.

Efficient Kinetic Measurements in Microreactors by in-line Raman Spectrometer

Monitoring of Kinetics in microreactors can be carried out by in-line Raman spectroscopy. Hereby, an efficient analysis of rapid and exothermal reactions can be achieved. Furthermore, a much faster and cost efficient analysis,  avoiding additional steps such as quenching, probe preparation and off-line analyses can be reached.

Process Raman Spectroscopy for the in-line Monitoring of aerob Fermentation 

Automated control of processes for the chemical and biotechnological industry requires measurement technologies, which directly [in-line or on-line] determine the reactands and products concentration. Furthermore, a direct and easy integration in the process plant is required. This poster describes the monitoring of a fermentation with an in-line Raman spectrometer.

Process Capable Raman Spectroscopy with High Optical Efficiency for in-line Analytics 

Established off-line methods for industrial monitoring of chemical reactions is increasingly replaced by optical online methods. A research project at University of Applied Sciences Mannheim developed a high efficient Raman setup based on 532nm laser excitation and tec5 operation electronics for S7031-1006S.