| 1. |
- Vera, C. M., et al.
(author)
-
A preliminary study on the selectivity of linear polynuclear aromatic hydrocarbons in SFC using phenyl-type stationary phases
- 2015
-
In: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 121, s. 136-140
-
Journal article (peer-reviewed)abstract
- The retention behaviour of a homologous series of polyaromatic hydrocarbons was evaluated on two phenyl-type stationary phases in reversed phase supercritical fluid chromatography (SFC). These phases were the Synergi polar-RP phase and the Cosmosil 5PBB phase, both of which are polar end-capped and incorporate an ether in a propyl chain that tethers the phenyl ring to the silica surface. The Cosmosil 5PBB phase also has five bromine atoms on the phenyl ring. The retention capacity of the Cosmosil column was substantially greater than the Synergi column. However, selectivity on the Cosmosil column was effectively independent of the acetonitrile modifier composition in the CO2 mobile phase, whereas, selectivity on the Synergi column was greatly affected by the acetonitrile modifier in the CO2 mobile phase. The results from this study showed that selectivity and retention studies in HPLC cannot be used to predict selectivity and retention behaviour in SFC. (C) 2015 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Samuelsson, Jörgen, 1971-, et al.
(author)
-
Viscosity contrast effects in analytical scale chromatography : Evidence and impact
- 2017
-
In: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 130, s. 102-107
-
Journal article (peer-reviewed)abstract
- The phenomenon known as viscous fingering has been shown to be very detrimental to separation performance in preparative and size exclusion chromatography, and also in multidimensional HPLC However, there are few reports of viscous fingering in analytical scale high performance liquid chromatography (HPLC), despite samples very often being introduced to the analytical-size HPLC columns in a solvent have a substantially different viscosity than the mobile phase. With this study we aim at first hand to investigate if viscous fingering or any similar and related effects to these in preparative levels also take place in analytical scale HPLC and if so, what impact this have on the separation performance. We could show that not only viscous finger does occur in analytical scale columns but also that peak distortions are apparent already at viscosity ratios between eluent and sample solution approaching unity. The latter indicates that a pre-viscous phenomenon is occurring that could be more important than the viscous fingering itself at the analytical format. As the viscosity contrast increases, the leading edge of the sample band distorts and the band volume increases, both leading to a decrease in performance.
|
|
| 3. |
- Shalliker, R. Andrew, et al.
(author)
-
Sample introduction for high performance separations
- 2016
-
In: TrAC. Trends in analytical chemistry. - : Elsevier. - 0165-9936 .- 1879-3142. ; 81, s. 34-41
-
Research review (peer-reviewed)abstract
- In this review we discuss how viscosity contrasts between the injection plug and the mobile phase may lead to loss in separation performance, especially in UHPLC columns or SFC environments. Firstly, the wall effect is discussed, and how it can amplify viscosity contrast effects. We then illustrate how viscosity contrasts lead to the phenomenon known as viscous fingering, and we detail the destructive effects of this phenomenon. We expand on the viscous fingering component, however, demonstrating that viscosity contrast effects begin to deteriorate performance long before the conditions are such that viscous fingering occurs. Subtle changes in band-shape are apparent even with very low viscosity contrasts. Lastly we illustrate how viscosity contrast effects lead to severe peak distortions in SFC. Analysts who seek high efficiency separations must make every effort to eliminate, or at least minimise the viscosity contrast between the injection plug and the mobile phase.
|
|
