Nonaqueous Capillary Electrochromatographic Separation of Synthetic Neutral Polymers by Size Exclusion Chromatography Using Polymeric Stationary Phases

Abstract

In this paper, we report the separations of large, neutral, synthetic polymers using primarily a nonaqueous mobile phase without the use of a supporting electrolyte. The size- exclusion-based mechanism for separation was achieved on sulfonated polystyrene/divinylbenzene stationary phases. The effect of water, voltage, stationary phase exchange capacity, and pore size were investigated. The stationary phase and solvent interactions were studied by attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) and a possible mechanism for the generation of EOF in the THF/water system is provided. Linear calibration curves were obtained for polystyrenes ranging in MW from 5K to 2M, for columns made using a combination of high capacity ion exchanger and a neutral polystyrene/divinylbenzene material of varied pore sizes. Analysis of polyurethane, polystyrene, and other polymer samples using CEC correlated well with results obtained by conventional HPLC. The size exclusion CEC separations provide an alternative mode for determining the relative molecular weights of polymers, with reduced solvent consumption.

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

“…For the fabrication of the columns, porous polymeric frits were made from poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) polymer (GMA-co-TRIM), using an in situ photoinitiated polymerization reaction as described by Svec et al [61,62], with some modifications to the procedure as detailed in [51]. For the 75 mm capillaries, a polymerization time of 45 min was found to produce sufficiently stable and porous frits, whereas for the 100 mm capillaries, 75 min was required.…”

“…For the 75 mm capillaries, a polymerization time of 45 min was found to produce sufficiently stable and porous frits, whereas for the 100 mm capillaries, 75 min was required. The X400-PLGel C columns used for the nonaqueous work were fabricated using the procedure provided in our earlier paper [51]. The preparation of X300 columns also followed a similar procedure with the following changes.…”

“…In order to expand the effective calibration range, we prepared a mixed-bed column consisting of the X400 resin and PL Gel Mixed C. The optimization of the column composition and method were presented in our previous paper, and the conditions used herewith were similar since we were analyzing the same order of MWs [51]. It should be noted that for the PIC derivatization method, the relative retention times were calculated by normalizing versus the methyl-phenylcarbamate (Me-PIC) peak resulting from quenching of the excess reagent with methanol, at the end of the reaction [69].…”

“…Size-based separation mechanisms have not been fully exploited in CEC, excluding capillary gel electrophoresis, which relies on sieving rather than size exclusion [47]. The only true size exclusion-based separations in a pure CEC mode, for MW neutral polymers, were reported by Venema et al and Stol et al, using bare silica columns [48][49][50] and by our group using polymeric stationary phases [51]. Peters et al [52] had demonstrated the separation of polystyrene standards on a methacrylate-based monolithic column.…”

Recent applications in capillary electrochromatography

“…SEEC has been used for the determination of the molarmass distributions of synthetic polymers [117,118]. Ding et al [117] used 5 mm Nucleosil stationary phase with 300 Å pores to construct a mass calibration curve with polystyrene standards.…”