Pressure, temperature and density drops along supercritical fluid chromatography columns. I. Experimental results for neat carbon dioxide and columns packed with 3- and 5-micron particles

Possibilities of retention modeling and computer assisted method development in supercritical fluid chromatography

“…The interconversion between isocratic and gradient retention data was found to be less straightforward than in RPLC and HILIC. This behavior is in agreement with our expectations since the pressure generated by the column may vary between the different isocratic and gradient conditions (different mobile phase viscosity, depending on the percentage of methanol) [2,26,27]. Considering that in SFC, pressure has a very strong impact on the mobile phase density and its eluent strength, the inevitable change in experienced pressure between an isocratic and a gradient run severely compromises retention prediction in SFC.…”

Performance of the same column in supercritical fluid chromatography and in liquid chromatography

“…This will lead to flow-rate dependent retention factors especially when the mobile phase conditions are close to the supercritical point. However, using higher back pressures, or with the use of a small amount of methanol as mobile phase modifier, this effect can be moderated [23,24]. Note that the density varies continuously with the local pressure along the column, thus the observed retention factors are apparent values originating from the sum of the local retention contributions along the column.…”

Theoretical evaluation of the advantages and limitations of constant pressure versus constant flow rate gradient elution separation in supercritical fluid chromatography

“…While in HPLC the density is nearly constant (except for ultra-high performance liquid chromatography conditions [6]), the mobile phase undergoes a significant decompression along the column axis in SFC [4,7]. This has a significant influence on retention.…”

“…For the sake of simplicity the influence of temperature was omitted and thus an isothermal column was assumed (explained further on). This isothermal assumption may become stressed at certain practical conditions [4,5] but it is sufficient to allow a comparative study between cP-and cF-mode. In general, the properties (using the values provided by NIST REFPROP software) were fitted to…”