Potential of vis–NIR spectroscopy to monitor the silica precipitation reaction

• Published in: Analytical and bioanalytical chemistry Vol. 409; no. 3; pp. 785 - 796
• Main Authors: Rey-Bayle, Maud, Bendoula, Ryad, Henrot, Serge, Lamiri, Kilani, Baco-Antoniali, Franck, Caillol, Noémie, Gobrecht, Alexia, Roger, Jean-Michel
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.01.2017; Springer; Springer Nature B.V; Springer Verlag
• Subjects: Aggregates; Analytical Chemistry; Biochemistry; Characterization and Evaluation of Materials; Chemical precipitation; Chemical properties; Chemistry; Chemistry and Materials Science; Engineering Sciences; Food Science; Laboratory Medicine; Methods; Monitoring; Monitoring/Environmental Analysis; Monitors; Near infrared radiation; Near infrared spectroscopy; Observations; Physical properties; Precipitation (Chemistry); Principal components analysis; Process Analytics in Science and Industry; Research Paper; Scattering; Scattering coefficient; Scattering coefficients; Silica; Silicon dioxide; Spectra; Spectroscopy; Spectrum analysis; Statistical process control; France; Collimated transmission; Monitoring silica precipitation; Physical properties; Scattering coefficients; Near-infrared spectroscopy
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-016-0064-1

Controlling production online is an important issue for chemical companies. Visible and near-infrared (NIR) spectroscopy offers a number of important advantages for process monitoring, and has been used since the 1980s. For complex media such as silica precipitation samples, it is interesting to be able to study independently the scattering and absorption effects. From the scattering coefficient it is possible to extract information on the physical structure of the medium. In this work, the physical changes were monitored during a silica precipitation reaction by simple measurement of collimated transmittance NIR spectra. It is shown that it is possible to differentiate samples before and after the gel point, which is a key parameter for monitoring the process. From these NIR spectra the scattering coefficients were simply extracted, allowing a global vision of the physical changes in the medium. Then principal component analysis of the spectra allowed refinement of the understanding of the scattering effects, in combination with particle size monitoring.