| 1. |
|
|
| 2. |
- Vera, C. M., et al.
(författare)
-
Contrasting selectivity between HPLC and SFC using phenyl-type stationary phases : A study on linear polynuclear aromatic hydrocarbons
- 2015
-
Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 119, s. 40-43
-
Tidskriftsartikel (refereegranskat)abstract
- A selectivity study was undertaken using two types of phenyl-type (Synergi polar RP and Cosmosil 5PBB) stationary phases in supercritical fluid chromatography. The mobile phases used in the SFC environment employed CO2 with methanol as the modifier. These columns were tested using linear polynuclear aromatic hydrocarbons as the test solutes. The retention behaviour of these PAHs in SFC was compared to their behaviour in HPLC and there were very distinct differences. On the Synergi-polar stationary phase the PAH selectivity was highly dependent on the methanol modifier concentration, but in comparison on the Cosmosil column, the selectivity between the members of this PAH test group showed almost no change as a function of the methanol concentration, even though the retentivity on the Cosmosil stationary phase was far greater than the Synergi stationary. In fact, the mobile phase played a very passive role in the separations observed on the Cosmosil stationary phase. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Vera, C. M., et al.
(författare)
-
Protocol for the visualisation of axial temperature gradients in ultra high performance liquid chromatography using infrared cameras
- 2018
-
Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 141, s. 141-147
-
Tidskriftsartikel (refereegranskat)abstract
- A protocol was developed for the visualisation of axial temperature gradients on a Kinetex column (1.3 μm C18 100 Å 50 × 2.1 mm) operated at near maximum pressure of the system (Pmax) using an infrared camera. Real time viscous frictional heating effects across the entire column length was observed, and showed that with increasing flow rate there was an increase in the maximum temperature of the column, and the difference between the inlet and outlet temperatures. Temperature profile data over the entire length of the column revealed the dynamics of heat exchange processes along different parts of the column, and raises the question on potential heating effects on eluents. The axial temperature gradients of eluents such as pure methanol, isopropyl alcohol and acetonitrile near Pmax were compared; finding that acetonitrile which had the highest flow velocity at Pmax gave the highest overall temperature increase for these eluents.
|
|
| 4. |
- Vera, C. M., et al.
(författare)
-
Visualisation of axial temperature gradients and heat transfer process of different solvent compositions in ultra high performance liquid chromatography using thermography
- 2019
-
Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 145, s. 927-935
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal imaging was used to visualise axial temperature gradients in chromatography columns running solvents of water, methanol and acetonitrile at various compositions. The non-monotonic relationship between solvent composition and viscosity enabled the testing of solvent conditions with equivalent viscosities, but with different percentages of water. It was observed that at equivalent power the increase in water composition leads to an increase in the magnitude of the axial temperature gradients (Delta T-A). Observing the change in temperature at defined points (Delta T-p) with increasing power indicates that the relationship between Delta T-p and power is not linear but deviates at higher power. The degree of this deviation depends on what point along the column axis is observed as well what solvent composition is used. Being able to monitor the entire length of the column using thermography also allowed for the observation of different rates of heat transfer through to the bulky stainless steel end fittings from solvent to solvent. Revealing that water is able to transfer heat to the stainless steel surface in such a way that the temperature profile of transition point between columns to end fitting is more gradual compared to when methanol or acetonitrile is used. This evidence plus video data collected indicates that at constant flow rate an equilibrium between heat generated and heat dissipated through the stainless steel is formed, which differs from solvent to solvent. Moreover any disruption to this equilibrium, i.e. a change in flow rate will momentarily change the shape of the temperature profile.
|
|
