Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7608977 | Journal of Chromatography A | 2018 | 13 Pages |
Abstract
An approach to conducting SFC separations under pseudo-adiabatic condition utilizing a dual-zone column heater is described. The heater allows for efficient separations at low pressures above the critical temperature by imposing a temperature profile along the column wall that closely matches that for isenthalpic expansion of the fluid inside the column. As a result, the efficiency loss associated with the formation of radial temperature gradients in this difficult region can be largely avoided in packed analytical scale columns. For elution of n-octadecylbenzene at 60â¯Â°C with 5% methanol modifier and a flow rate of 3â¯mL/min, a 250â¯Ãâ¯4.6-mm column packed with 5-micron Kinetex C18 particles began to lose efficiency (8% decrease in the number of theoretical plates) at outlet pressures below 142â¯bar in a traditional forced air oven. The corresponding outlet pressure for onset of excess efficiency loss was decreased to 121â¯bar when the column was operated in a commercial HPLC column heater, and to 104â¯bar in the new dual-zone heater operated in adiabatic mode, with corresponding increases in the retention factor for n-octadecylbenzene from 2.9 to 6.8 and 14, respectively. This approach allows for increased retention and efficient separations of otherwise weakly retained analytes. Applications are described for rapid SFC separation of an alkylbenzene mixture using a pressure ramp, and isobaric separation of a cannabinoid mixture.
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Shawn C. Helmueller, Donald P. Poe, Krzysztof Kaczmarski,