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Dynamic pH determination at high pressure of aqueous additive mixtures in contact with dense CO2
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.ORCID iD: 0000-0002-3966-0220
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.ORCID iD: 0000-0003-2744-1634
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2018 (English)In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 136, p. 95-101Article in journal (Refereed) Published
Abstract [en]

A system consisting of a high-pressure tolerant microfluidic glass chip, high-speed absorbance imaging, and image processing has been developed to study rapid dynamic events like pH change in a multiphase flow. The system gives both kinetic and quantitative equilibrated information. By tracking the interactions of aqueous additive mixtures and liquid CO2, at 80 bar and 24 °C, under flow, measurement at a given P, T condition is done in 0.25 s. The acidification rate to steady state was found to be mass transport limited, occurring in less than 1 s. For 30 mM of the additives ammonium acetate and ammonium formate, equilibrium pH of 4.5 and 4.1, respectively, was seen. These additives are of key importance in common mobile phases used in SFC.

Place, publisher, year, edition, pages
2018. Vol. 136, p. 95-101
Keywords [en]
Supercritical fluid chromatography, High-pressure microfluidics, Additive salts, Dense CO, Multiphase flow, Image analysis
National Category
Chemical Engineering Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-353940DOI: 10.1016/j.supflu.2018.02.012ISI: 000430767400011OAI: oai:DiVA.org:uu-353940DiVA, id: diva2:1219869
Funder
Knut and Alice Wallenberg FoundationAvailable from: 2018-06-18 Created: 2018-06-18 Last updated: 2018-08-02Bibliographically approved
In thesis
1. Microfluidics at High Pressures: Understanding, Sensing, and Control
Open this publication in new window or tab >>Microfluidics at High Pressures: Understanding, Sensing, and Control
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis explores understanding, sensing, and control in high-pressure microfluidics. The high-pressure regime allows fluids to be forced through narrow channels at substantial speed and creates conditions for fluids of high density and low viscosity—features desired in flow-based chemical analyses. With changes to pressure and temperature, fluid properties vary, and for miniaturized flow systems, sensing and control are needed.

For miniaturized chemical analytics to utilize high-pressure fluids, like supercritical CO2, sensors are required for flow characterization. In this thesis, high-pressure tolerant sensors in glass chips have been developed and investigated. By the use of chip-integrated temperature, flow, and relative permittivity sensors, the variable behavior of supercritical CO2 or binary component CO2-alcohol mixtures have been investigated. To be able to change flow rates, a heat-based actuator chip has been developed. By a flow control system, which combines a relative permittivity sensor and heat actuated flow regulators on a modular system, the composition of binary component CO2-alcohol mixtures can be tuned and controlled with feedback.

Flows of multiphase CO2-H2O hold promise for miniaturized extraction systems. In this thesis, parallel multiphase CO2-H2O flow has been studied. To achieve control, methods have been investigated where channels have been modified by the introduction of a guiding ridge and altered by a chemical coating. Flow is a dynamic process, where pressure and temperature can vary with time and place. As the properties of fluids containing CO2 may change with pressure and temperature, properties will also change with time and place. Because of this, instruments with spatial and temporal resolution are needed to better understand dynamic chemical effects at flow. In this thesis, a tool is presented to study the dynamic acidification of aqueous solutions that come in contact with flowing CO2.

By a study performed to understand the strength and pressure tolerance of glass chips, it has been found that the fracture is not only determined by the applied pressure, but also on time and environment.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 60
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1687
Keywords
High-pressure microfluidics, supercritical CO2, compressible flow, relative permittivity, integrated electrodes
National Category
Chemical Engineering Materials Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-353964 (URN)978-91-513-0372-7 (ISBN)
Public defence
2018-09-14, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2018-08-21 Created: 2018-06-19 Last updated: 2018-08-27

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Publisher's full texthttp://www.sciencedirect.com/science/article/pii/S0896844617309385

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Andersson, MartinHjort, KlasKlintberg, Lena

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