Peroxodisulfate as a chemical initiator for methacrylate‐ester monolithic columns for capillary electrochromatography

Abstract

Organic monolithic stationary phases for CEC were synthesized in situ in fused-silica capillaries. Polymerization mixtures were composed of butyl methacrylate, ethylene dimethacrylate, and [2-(methacryloyloxy)ethyl]trimethyl ammonium chloride in the presence of a porogenic solvent, using ammonium peroxodisulfate as chemical initiator, and N,N,N',N'-tetramethylethylenediamine to activate the reaction. The influence of the amount of initiator, temperature, and composition of porogenic solvent on the physical and chromatographic properties of monolithic stationary phases has been investigated. A minimum plate height of 14.5 microm was obtained at 18 wt% of 1,4-butanediol in the polymerization mixture. The produced monolithic stationary phases exhibited a good repeatability and batch-to-batch and mixture-to-mixture reproducibility, with RSD values below 5.6% in the electrochromatographic parameters studied. A comparison with columns prepared by thermal initiation with alpha,alpha'-azobisisobutyronitrile (AIBN) was also performed. The most efficient column initiated with peroxodisulfate showed better efficiencies and selectivities than that prepared with AIBN at the same composition mixture.

Lauroyl peroxide as thermal initiator of lauryl methacrylate monolithic columns for CEC

“…1,4-Butanediol content in the polymerization mixture (wt%) this purpose, the initial polymerization mixture chosen was the optimum one found in the previous section, but replacing AIBN by LPO. Several reports [4,6,10,32,49] have demonstrated that the morphology of a methacrylate ester-based monolithic column could be tailored by changes in polymerization conditions. In the present study, the influence of the initiator percentage and the porogenic solvent composition on the porous properties and electrochromatographic performance of LMA-based monolithic columns was investigated.…”

“…Other less common approaches to initiate the polymerization are the use of g-radiation [27-30] or a chemical agent [31]. Recently, we have described employing a chemical system composed of ammonium peroxodisulfate and TEMED as a promising alternative to AIBN as initiator for the preparation of BMA-, butyl acrylate-and hexyl methacrylate-based monolithic columns for CEC [32][33][34]. Monoliths obtained with this initiation system showed important differences in morphology compared with those prepared with AIBN as thermal initiator.…”

Chemical initiation for butyl and lauryl acrylate monolithic columns for CEC

“…Recently, we have described the employ of a chemical system composed of ammonium peroxodisulfate and TEMED as initiator for the preparation of butyl methacrylate-, BA-and hexyl methacrylate-based monoliths and using ethylene dimethacrylate (EDMA) as crosslinker [19][20][21]. Although CEC performance of methacrylate-based monolithic beds obtained with this system was comparable to that achieved for monoliths thermally initiated with AIBN [8,10], in the case of BA stationary phases, the resulting columns exhibited slightly lower efficiency values than those previously reported by other groups [4,9,11].…”

CEC column behaviour of butyl and lauryl methacrylate monoliths prepared in non‐aqueous media

“…These polymeric monoliths are usually prepared by in situ polymerization of a mixture composed of functional monomer/s, cross-linker, porogens, and a free radical initiator. Polymerization is commonly initiated thermally [12,[14][15][16][19][20][21][22][23][24][25][26][27], by UV irradiation [10,11,13,15,17,19,22,24], or by a chemical system [18,28,29].Up to now, most of the publications dealing with the development of monolithic columns are focused on the optimization of the composition of the polymerization mixture, changing factors such as the type of the monomer, the degree of cross-linking, the composition and concentration of the porogenic solvent, and the type of initiation. These variables have shown to have influence on porous properties of monoliths and consequently their chromatographic features.…”