th - 1987 - 51st ENC Conference
th - 1987 - 51st ENC Conference
th - 1987 - 51st ENC Conference
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MFI<br />
FLOW NMR STUDIES OF SUPERCRITICAL FLUIDS<br />
by<br />
L. Allen*, T. Glass, and H.C. Dorn<br />
Department of Chemistry<br />
Virginia Polytechnic Institute<br />
And State University<br />
B1acksburg, Virginia 24061<br />
PH (703) g61-5953<br />
Supercrltlcal (SC) fluids (e.g, CO 2) have become increasing important in<br />
chromatographic separations. The physical characteristics of <strong>th</strong>ese dense<br />
gases (e.g., hlgh density and low viscosity) a11ow studies of different<br />
dynamic flow patterns. That is, It is readily possible to vary pressure,<br />
temperature, and flow rates for SC fluids, <strong>th</strong>ereby, allowing studies of flow<br />
patterns ranging from laminar to turbulent flow. In addition, previous<br />
studies in our laboratory I allow accurate ma<strong>th</strong>ematical modeling of a given<br />
flow pattern provtded <strong>th</strong>at spin lattice relaxation (T1) data is known. To<br />
<strong>th</strong>is end, we have also developed techniques for conveniently measuring (T1'2)<br />
tn flowing liquids.<br />
It should also be noted <strong>th</strong>at supercritical fluids are potentially useful<br />
for studying quadrupolar nuclei (e.g., 14N and 170) and significant<br />
enhancements in resolution are feasible. That Is, <strong>th</strong>e lower viscosities of SC<br />
fluids (and corresponding change in correlation times, FC) reduce <strong>th</strong>e<br />
efficiency of quadrupolar relaxation as recently reported 2.<br />
In <strong>th</strong>is presentation, we wlll report 200 MHz IHNMR data (including T 1<br />
relaxation times) for several compounds in flowing supercritical liquids.<br />
Also various SC flow patterns will be presented and compared wi<strong>th</strong> normal<br />
liquid results.<br />
1. James F. Haw, Ph.D. Thesis, Virginia Tech, (1982).<br />
2. Robert, J.M.; Evtlta, R.F.J. Am. Chem. Soc. (1984), 107,<br />
3733.
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