Cross-linker effects on the separation efficiency on (poly)methacrylate capillary monolithic columns. Part I. Reversed-phase liquid chromatography

Abstract

We synthesized 8 polymethacrylate monolithic capillary columns using laurylmethacrylate functional monomer and various cross-linking monomers differing in the polarity and size. The efficiency of monolithic columns for low-molecular compounds significantly improved with increasing number of repeat non-polar methylene groups in the cross-linker molecules, correlating with greater proportion of small pores with size less than 50 nm. The best efficiency with HETP=25 μm for alkylbenzenes was achieved for columns prepared using hexamethylene dimethacrylate (HEDMA). Columns prepared with polar (poly)oxyethylene dimethacrylate cross-linkers show also improved efficiency with increasing chain length and generally better performance in comparison to the (poly)methylene dimethacrylate cross-linkers of comparable size, however with less apparent effects of the chain lengths on the pore distribution. The monolithic columns prepared with tetraoxyethylene dimethacrylate (TeEDMA) showed the best efficiency of all the columns tested, corresponding to HETP=15 μm (approx. 70,000 theoretical plates/m), show excellent column-to-column reproducibility with standard deviations of 2.5% in retention times, good permeability and low mass transfer resistance, so that is suitable for fast separation of low-molecular compounds in 2 min or less. By modification of the fused-silica capillary inner walls pre-treatment procedure, very good long-term stability was achieved even in 0.5 mm i.d. capillary format. The TeEDMA column can be also used for size-exclusion chromatography of lower non-polar synthetic polymers, whereas it is less suitable for separations of proteins than the HEDMA column.

Monolithic capillary columns based on pentaerythritol acrylates for molecular‐size‐based separations of synthetic polymers

“…Using light scattering detection (LSD), it would be possible to distinguish between the cases, but detection cell volume of currently LSD incompatible with capillary columns used in the study. Anyway, the monolithic column prepared in this work can separate twice as much polystyrene standards in one run as the counterparts reported in the literature [22,24] and their almost linear calibration curves makes them attractive for the polymer analysis over broad range of molar mass.…”

Development of an online solid-phase extraction with liquid chromatography method based on polymer monoliths for the determination of dopamine

“…Robustness of prepared monolithic stationary phases is a very important characteristics when considering future application of any developed method. Both polymethacrylate and styrene‐based monoliths already proved to be highly robust stationary phases providing comparable stability to commercially available columns packed with particulate stationary phases . Figure demonstrates that 4‐vinylphenylboronic acid monolith lost its extraction power after more than 90 analyses that corresponds to 3000 μL of sample flushed through the extraction column and 0.9 μg of dopamine mass loaded in a total.…”

The Effects of the Column Length on the Efficiency of Capillary Zwitterionic Organic Polymer Monolithic Columns in HILIC Chromatography

“…The capillaries were kept for 20 h at 60 °C in a circulated-air thermostat. After the end of the polymerization reaction, the ends of the capillary were cut to the desired column length; the capillary monolithic column was washed with acetonitrile and finally with the mobile phase, as described in more detail elsewhere [13].…”