Highly Sensitive Raman Spectroscopy with Low Laser Power for Fast In-Line Reaction and Multiphase Flow Monitoring

Braun, Frank; Schwolow, Sebastian; Seltenreich, Julia; Kockmann, Norbert; Röder, Thorsten; Gretz, Norbert; Rädle, Matthias

doi:10.1021/acs.analchem.6b01509

Cited by 26 publications

(18 citation statements)

References 37 publications

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“…There have been a number of studies carried out using Raman or MIR spectroscopy for reaction monitoring [3,6,[10][11][12][13]. In order to analyze multicomponent mixtures, optical spectroscopy in conjunction with chemometric techniques is often required for converting optical spectra into analyte concentrations [14,15].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Raman and Mid-Infrared Spectroscopy for Real-Time Monitoring of Yeast Fermentations: A Proof-of-Concept for Multi-Channel Photometric Sensors

et al. 2019

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Raman and mid-infrared (MIR) spectroscopy are useful tools for the specific detection of molecules, since both methods are based on the excitation of fundamental vibration modes. In this study, Raman and MIR spectroscopy were applied simultaneously during aerobic yeast fermentations of Saccharomyces cerevisiae. Based on the recorded Raman intensities and MIR absorption spectra, respectively, temporal concentration courses of glucose, ethanol, and biomass were determined. The chemometric methods used to evaluate the analyte concentrations were partial least squares (PLS) regression and multiple linear regression (MLR). In view of potential photometric sensors, MLR models based on two (2D) and four (4D) analyte-specific optical channels were developed. All chemometric models were tested to predict glucose concentrations between 0 and 30 g L−1, ethanol concentrations between 0 and 10 g L−1, and biomass concentrations up to 15 g L−1 in real time during diauxic growth. Root-mean-squared errors of prediction (RMSEP) of 0.68 g L−1, 0.48 g L−1, and 0.37 g L−1 for glucose, ethanol, and biomass were achieved using the MIR setup combined with a PLS model. In the case of Raman spectroscopy, the corresponding RMSEP values were 0.92 g L−1, 0.39 g L−1, and 0.29 g L−1. Nevertheless, the simple 4D MLR models could reach the performance of the more complex PLS evaluation. Consequently, the replacement of spectrometer setups by four-channel sensors were discussed. Moreover, the advantages and disadvantages of Raman and MIR setups are demonstrated with regard to process implementation.

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Section: Introductionmentioning

confidence: 99%

Comparison of Raman and Mid-Infrared Spectroscopy for Real-Time Monitoring of Yeast Fermentations: A Proof-of-Concept for Multi-Channel Photometric Sensors

et al. 2019

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“…The area and sensitivity gain lead to a considerable increase in measurement speed. Spectral information is lost, but this can be of minor importance for known materials [18,26].…”

Section: Raman Scanning Image Analysismentioning

confidence: 99%

Molecule Sensitive Optical Imaging and Monitoring Techniques—A Review of Applications in Micro-Process Engineering

2020

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This paper provides an overview of how molecule-sensitive, spatially-resolved technologies can be applied for monitoring and measuring in microchannels. The principles of elastic light scattering, fluorescence, near-infrared, mid-infrared, and Raman imaging, as well as combination techniques, are briefly presented, and their advantages and disadvantages are explained. With optical methods, images can be acquired both scanning and simultaneously as a complete image. Scanning technologies require more acquisition time, and fast moving processes are not easily observable. On the other hand, molecular selectivity is very high, especially in Raman and mid-infrared (MIR) scanning. For near-infrared (NIR) images, the entire measuring range can be simultaneously recorded with indium gallium arsenide (InGaAs) cameras. However, in this wavelength range, water is the dominant molecule, so it is sometimes necessary to use complex learning algorithms that increase the preparation effort before the actual measurement. These technologies excite molecular vibrations in a variety of ways, making these methods suitable for specific products. Besides measurements of the fluid composition, technologies for particle detection are of additional importance. With scattered light techniques and evaluation according to the Mie theory, particles in the range of 0.2–1 µm can be detected, and fast growth processes can be observed. Local multispectral measurements can also be carried out with fiber optic-coupled systems through small probe heads of approximately 1 mm diameter.

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“…Thanks to the cooperation with Hochschule fur Technik in Mannheim [29][30][31], visualization studies of the movement of gas bubbles in the microreactor -channel with a diameter of 1 mm were carried out (Fig. 12).…”

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confidence: 99%

Application of videogrammetry in the mechanics of multi-phase systems

Anweiler

Ulbrich

2020

THERM SCI

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This paper is a description of the evolution of long-term research work on two-phase flows using parallel studies of dynamic image analysis and stochastic processes analysis. The state of current knowledge on the research of gas-solid and gas-liquid systems as well as a review of research relating to these issues are also presented. The work grants the principles of videogrammetric surveys based on stochastic analysis for a series of photographs taken with video techniques. The method applies the analysis of changes in selected features and parameters in the time domain. Especially in application to multiphase gas-liquid and solid-gas mixture flows, which are characterized by strong variabilities. Parameters such as flow patterns of the mixture were determined as time-space distributions of phase concentration, displacement velocities of separated two-phase structures, volume partitions of phases, and velocity field distributions are evaluated. The changes of certain parameters characterizing the flow in the time domain often hide more useful information. The subject of this study covers the basics of videogrammetry with a description of two-phase mixture motion for co-current flow in channels, mapping of the phase velocity field, also across the tube bundle in shell-and-tube apparatus, phase motion at the flow of a two-phase gas-liquid mixture in mini-channels, transport of liquids in air-lift pump and fluidization of solid particles.

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Highly Sensitive Raman Spectroscopy with Low Laser Power for Fast In-Line Reaction and Multiphase Flow Monitoring

Cited by 26 publications

References 37 publications

Comparison of Raman and Mid-Infrared Spectroscopy for Real-Time Monitoring of Yeast Fermentations: A Proof-of-Concept for Multi-Channel Photometric Sensors

Comparison of Raman and Mid-Infrared Spectroscopy for Real-Time Monitoring of Yeast Fermentations: A Proof-of-Concept for Multi-Channel Photometric Sensors

Molecule Sensitive Optical Imaging and Monitoring Techniques—A Review of Applications in Micro-Process Engineering

Application of videogrammetry in the mechanics of multi-phase systems

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