Categories
Monoliths

Crosslinking monomer: another way how to improve column efficiency

From my point of view, the preparation of polymer monolithic stationary phases suitable for the separation of small molecules is one of the hotter topics now in monolithic chromatography. There are several ways how to improve their separation power for small molecules. It is possible to increase their surface area either by hypercrosslinking modification or with the combination of non-polar and polar monomers. Another possibility is to prepare low-surface area (but efficient) materials by the termination of the polymerization reaction at the early stages or by application of crosslinking monomer with longer atom chain in between two methacrylate units.

We have extended the later approach and recently published the article describing the one-step preparation of highly efficient columns for the separation of small molecules.

Categories
Monoliths

Remotely detected NMR and hypercrosslinked monoliths

During the time I spent in Berkeley I had the honor to work on the beginning of the project leading to the portable system for highly sensitive multi-dimensional chemical analysis. This work included hyphenation of NMR with liquid chromatography separation using organic polymer monoliths.

Categories
Monoliths Theory

Separation of small molecules: surface area vs. gel porosity

Generally, methacrylic acid is used as a charge-bearing agent for generation of electroosmotic flow in capillary electrochromatography. However, methacrylic acid has a significant effect on the morphology of the monolithic stationary phases based on styrene – divinylbenzene system as showed recently by group in Prague.

The monolithic material prepared without methacrylic acid in the polymerization mixture showed a very low surface area of 0.1 m2/g, whereas the surface area of organic polymer monolith with methacrylic acid increased significantly up to 261 m2/g. The addition of methacrylic acid in to the polymerization mixture improves also separation power of prepared monolithic columns. Figure 1 shows the separation of the mixture of small molecules on the column without (A) and with (B) methacrylic acid in the polymerization mixture.

Categories
Monoliths

One column fits all – Hypercrosslinked monoliths

One column fits all was title of my poster presented at HPLC 2010 in Boston that described the preparation and characterization of hypercrosslinked monolithic stationary phases and their application in several chromatographic modes. We summarized poster’s results and submitted them as a paper in Journal of Chromatography A.

Categories
Monoliths

Separation of small molecules on organic polymer monoliths

Because of lack of small pores it is difficult to separate small molecules with polymer monoliths in isocratic mode. We have prepared monolithic capillary columns and then hypercrosslinked them to afford a monolith containing an array of small pores [1].