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A rapid-mixing design for conventional NMR probes
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.ORCID iD: 0000-0002-0231-3970
2005 (English)In: Journal of magnetic resonance (San Diego, Calif. 1997: Print), ISSN 1090-7807, E-ISSN 1096-0856, Vol. 175, no 2, 264-270 p.Article in journal (Refereed) Published
Abstract [en]

A simple stopped-flow design for rapid mixing of two liquids within the NMR probe is presented. The device uses no switches or relays but exploits instead the torque exerted by the magnetic field on a current-leading-coil to open and close the start and stop valves. Two serially arranged tangential jet mixer blocks provide a homogeneous mixture with, depending on conditions and requirements, a filling time in the 50-100 ms range and a subsequent stabilization time in the range of 10-40 ms as tested by mixing various combinations of liquids and observing their 1H NMR spectrum. Factors influencing the mixing process are analyzed.

Place, publisher, year, edition, pages
2005. Vol. 175, no 2, 264-270 p.
Keyword [en]
Alanine; Ethanol; Ethylene glycol; Homogeneous mixture; Mixing time; Pressure; Stopped-flow; Torque; Turbulent flow; Water
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-5530DOI: 10.1016/j.jmr.2005.04.012ISI: 000231082900011ScopusID: 2-s2.0-21244460805OAI: diva2:9926
QC 20100825Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-08-25Bibliographically approved
In thesis
1. NMR Studies of Colloidal Systems in and out of Equilibrium
Open this publication in new window or tab >>NMR Studies of Colloidal Systems in and out of Equilibrium
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The Thesis describes (i) the development of add-on instrumentation extending the capabilities of conventional NMR spectrometers and (ii) the application of the designed equipments and techniques for investigating various colloidal systems. The new equipments are:

Novel designs of stopped-flow and temperature–jump inserts intended for conventional Bruker wide-bore superconductive magnets. Both inserts are loaded directly from above into the probe space and can be used together with any 10 mm NMR probe with no need for any auxiliary instruments.

A set of 5 mm and 10 mm 1H – 19F – 2H NMR probes designed for heteronuclear 1H – 19F cross-relaxation experiments in Bruker DMX 200, AMX 300 and DMX 500 spectrometers, respectively.

A two–stage low-pass filter intended for suppressing RF noise in electrophoretic NMR experiments.

The kinetics of micellar dissolution and transformation in aqueous solutions of sodium perfluorooctanoate (NaPFO) is investigated using the stopped-flow NMR instrument. The sensitivity of NMR as detection tool for kinetic processes in micellar solutions is clarified and possible artefacts are analysed. In the NaPFO system, the micellar dissolution is found to proceed faster than 100 ms while surfactant precipitation occurs on the time scale of seconds-to-minutes. The kinetics of the coil-to–globule transition and intermolecular aggregation in a poly (Nisopropylacrylamide) solution are investigated by the temperature-jump NMR instrument. As revealed by the time evolution of the 1H spectrum, the T2 relaxation time and the self-diffusion coefficient D, large (>10 nm) and compact aggregates form in less than 1 second upon fast temperature increase and dissolve in less than 3 seconds upon fast temperature decrease.

The intermolecular 1H – 19F dipole-dipole cross-relaxation between the solvent and solute molecules, whose fast rotational diffusion is in the extreme narrowing limit, is investigated. The solutes are perfluorooctanoate ions either in monomeric or in micellar form and trifluoroacetic acid and the solvent is water. The obtained cross-relaxation rates are frequency-dependent which clearly proves that there is no extreme narrowing regime for intermolecular dipole-dipole relaxation. The data provide strong constraints for the dynamic retardation of solvent by the solute.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 55 p.
Trita-FYK, 0601
stopped-flow NMR, temperature-jump NMR, crossrelaxation, NMR, NMR probe, fluorosurfactant, micellar kinetics, micellar structure
National Category
Physical Chemistry
urn:nbn:se:kth:diva-3898 (URN)91-7178-310-5 (ISBN)
Public defence
2006-04-20, Sal F3, Lindstedtsvägen 26, 10:00
QC 20100929Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-09-29Bibliographically approved

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