Preparation and characterization of octadecyl acrylate monoliths for capillary electrochromatography by photochemical, thermal, and chemical initiation†

Abstract

Monolithic stationary phases based on octadecyl acrylate for CEC using different initiating systems (UV irradiation, thermal, and chemical initiation) in the presence of lauroyl peroxide as initiator were synthesized. For each initiation mode, the influence of the porogenic solvent composition on both the morphological and electrochromatographic properties of the resulting monoliths was investigated. Under optimal conditions, excellent efficiencies for the photochemically and chemically polymerized monoliths (minimum plate heights of 6.9-10.7 and 6.5-12.6 μm, respectively) were achieved. Thermally initiated columns gave lower efficiency values, permeabilities, and longer analysis times compared to these initiating systems. The produced monolithic stationary phases were evaluated in terms of reproducibility and gave RSD values below 9.2, 10.6, and 9.8% for UV, thermally, and chemically initiated columns, respectively.

New vinylester‐based monoliths as a new stationary phase for capillary electrochromatography

“…The permeabilities ranging between 1.5 × 10 −14 and 8.5 × 10 −14 m 2 were reported for the silica-based monoliths used in pressure-driven liquid chromatographic separations [4,[24][25][26][27][28][29]. The permeabilities of the capillary monoliths used in electrochromatographic separations were slightly higher and typically in the range of 5 × 10 −14 -20 × 10 −14 m 2 [30][31][32][33]. In the case of vinyl esterbased monoliths synthesized in this study, the permeability values in Table 1 are reasonably higher compared with the polymer or silica-based capillary monoliths previously used in different electrochromatographic separations [30][31][32][33].…”

“…The permeabilities of the capillary monoliths used in electrochromatographic separations were slightly higher and typically in the range of 5 × 10 −14 -20 × 10 −14 m 2 [30][31][32][33]. In the case of vinyl esterbased monoliths synthesized in this study, the permeability values in Table 1 are reasonably higher compared with the polymer or silica-based capillary monoliths previously used in different electrochromatographic separations [30][31][32][33]. Note that, the permeabilities of hybrid C8-silica monoliths synthesized as stationary phase for CEC are reasonably close to the values reported for vinyl ester-based monoliths synthesized in our study [34].…”

Monitoring the morphology development of polymer-monolithic stationary phases by thermal analysis

“…The efficiency and permeability of monolithic stationary phases is related to the domain size represented by the combined macropore and polymer microglobule sizes . A better understanding of the polymerization and phase separation processes may lead to the development of novel monolithic materials improving the chromatographic performance and possibly enlarging the application range.…”

Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC

“…Also, the efficiency of a photoinitiator depends on its absorption spectrum (absorption bands and the corresponding extinction coefficients, ε) [14,16], Thus, a large amount of initiated polymer nuclei could be obtained by a conjunction of high ε at the irradiation wavelength, high dissociation quantum yields and reactivity of the key radicals towards the monomer. Among UV photo-initiators employed to prepare polymeric monoliths, α,α´azobisisobutyronitrile (AIBN) has been used to conduct this process at 365 nm (close to its maximum absorption [17]), and at 254 nm [13,18]. Another photoinitiator widely used is 2,2-dimethoxy-2-phenylacetophenone (DMPA or Irgacure 651) [19][20][21][22].…”