Introducing Diffusing Wave Spectroscopy as a Process Analytical Tool for Pharmaceutical Emulsion Manufacturing

Reufer, Mathias; Machado, Alexandra H. E.; Niederquell, Andreas; Bohnenblust, Katharina; Müller, Beat; Völker, Andreas Charles; Kuentz, Martin

doi:10.1002/jps.24197

Cited by 28 publications

(16 citation statements)

References 51 publications

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“…Continuous DWS analysis during generation of pharmaceutical emulsions can give data about optimal homogenization conditions, showing when to stop the manufacturing process in order to prevent overprocessing of emulsions. Emulsion dynamics correlated with static analysis were in agreement with the modification of the droplet size distribution, during emulsion generation [175].…”

Section: Spectral Properties Of Emulsionssupporting

confidence: 72%

Spectral Properties of Foams and Emulsions

2021

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The optical and spectral properties of foams and emulsions provide information about their micro-/nanostructures, chemical and time stability and molecular data of their components. Foams and emulsions are collections of different kinds of bubbles or drops with particular properties. A summary of various surfactant and emulsifier types is performed here, as well as an overview of methods for producing foams and emulsions. Absorption, reflectance, and vibrational spectroscopy (Fourier Transform Infrared spectroscopy-FTIR, Raman spectroscopy) studies are detailed in connection with the spectral characterization techniques of colloidal systems. Diffusing Wave Spectroscopy (DWS) data for foams and emulsions are likewise introduced. The utility of spectroscopic approaches has grown as processing power and analysis capabilities have improved. In addition, lasers offer advantages due to the specific properties of the emitted beams which allow focusing on very small volumes and enable accurate, fast, and high spatial resolution sample characterization. Emulsions and foams provide exceptional sensitive bases for measuring low concentrations of molecules down to the level of traces using spectroscopy techniques, thus opening new horizons in microfluidics.

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Section: Spectral Properties Of Emulsionssupporting

confidence: 72%

Spectral Properties of Foams and Emulsions

2021

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“…DWS also has practical applications in the pharmaceutical and cosmetic industries as well (Reufer et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

diwanalr: An R data analysis package for diffusing-wave spectroscopy

Watkins¹

2019

JOSS

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“…Either translations of the sample cell or rotations of an opaque disc can also be employed for ensemble-averaging using echo techniques, [23] yielding ensemble-averaged correlation functions at long time scales and with excellent statistics. [22,24] While these ensemble-averaging techniques could in principle also be incorporated into a standard goniometer setup, we choose an alternative method, socalled Pusey-averaging. This method uses the measured time-averaged correlation function and the measured ensemble-averaged scattered intensity together with a simple theoretical treatment to provide the ensembleaveraged correlation function.…”

Section: Experimental: Materials and Methodsmentioning

confidence: 99%

Diffusing-wave spectroscopy in a standard dynamic light scattering setup

et al. 2017

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Diffusing-Wave Spectroscopy (DWS) extends dynamic light scattering measurements to samples with strong multiple scattering. DWS treats the transport of photons through turbid samples as a diffusion process, thereby making it possible to extract the dynamics of scatterers from measured correlation functions. The analysis of DWS data requires knowledge of the path length distribution of photons traveling through the sample. While for flat sample cells this path length distribution can be readily calculated and expressed in analytical form, no such expression is available for cylindrical sample cells. DWS measurements have therefore typically relied on dedicated setups that use flat sample cells. Here we show how DWS measurements, in particular DWS-based microrheology measurements, can be performed in standard dynamic light scattering setups that use cylindrical sample cells. To do so we perform simple random walk simulations which yield numerical predictions of the path length distribution as a function of both the transport mean free path and the detection angle. This information is used in experiments to extract the mean-square displacement of tracer particles in the material, as well as the corresponding frequency-dependent viscoelastic response. An important advantage of our approach is that by performing measurements at different detection angles, the average path length through the sample can be varied. Using measurements on a single sample cell, this gives access to a wider range of length and time scales than obtained in a conventional DWS setup. Such angle-dependent measurements also offer an important consistency check, as for all detection angles the DWS analysis should yield the same tracer dynamics, even though the respective path length distributions are very different. We validate our approach by performing measurements both on aqueous suspensions of tracer particles and on solid-like gelatin samples, for which we find our DWS-based microrheology data to be in very good agreement with rheological measurements performed on the same samples.

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Introducing Diffusing Wave Spectroscopy as a Process Analytical Tool for Pharmaceutical Emulsion Manufacturing

Cited by 28 publications

References 51 publications

Spectral Properties of Foams and Emulsions

Spectral Properties of Foams and Emulsions

diwanalr: An R data analysis package for diffusing-wave spectroscopy

Diffusing-wave spectroscopy in a standard dynamic light scattering setup

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