Beyond Karl Fischer titration: a monolithic quantum cascade sensor for monitoring residual water concentration in solvents
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Date
2023-03-28
Authors
Pilat, Florian
Schwarz, Benedikt
Baumgartner, Bettina
Ristanic, Daniela
Detz, Hermann
Andrews, Aaron Maxwell
Lendl, Bernhard
Strasser, Gottfried
Hinkov, Borislav
ORCID
0000-0002-4167-3653Advisor
Referee
Mark
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
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Abstract
Quality control of liquids is an important part of analytical chemistry. The gold standard for measuring residual water in organic solvents and pharmaceutical applications is Karl Fischer titration. It has a high sensitivity, selectivity and accuracy. The downsides are a time-consuming offline analysis, together with the need for toxic reagents producing waste, and it suffers from poor inter-laboratory reproducibility. In this work, we present a high-performance lab-on-a-chip sensor exploiting mid-IR spectroscopy for liquid sensing. It is operating at 6.1 mu m wavelength and is suitable for robust and flexible real-time in situ analysis of the residual water concentration in isopropyl alcohol. This is demonstrated in two experiments. A custom-made 60 mu L flow cell is employed to measure only minute amounts of analyte in an inline configuration. In a second approach, the whole sensor is immersed into the analyte to demonstrate sensitive and rapid in situ operation on the millisecond time scale. This is confirmed by the ability for time resolved single water-droplet monitoring, while they are mixed into the liquid sample. We obtain a limit of detection between 120 ppm and 150 ppm with a concentration coverage spanning three orders of magnitude from 1.2 x 10(-2)%(vol) to 25%(vol) for the flow cell and 1.5 x 10(-2)%(vol) to 19%(vol) in the in situ configuration, respectively.
Description
Citation
LAB ON A CHIP. 2023, vol. 23, issue 7, p. 1816-1824.
https://pubs.rsc.org/en/content/articlelanding/2023/LC/D2LC00724J
https://pubs.rsc.org/en/content/articlelanding/2023/LC/D2LC00724J
Document type
Peer-reviewed
Document version
Published version
Date of access to the full text
Language of document
en