Capillary-based solid-phase extraction with columns prepared using different bead trapping methods

Abstract

Three approaches of bead immobilization for CEC column preparation in a capillary were examined for SPE. The three approaches included a packed column with a single frit, a packed column with an inlet and outlet frit, and an entrapped column where beads were immobilized within an organic polymer. A direct comparison of SPE/preconcentration of 4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionic acid with a 2 cm long bed showed that the entrapped column yielded the best performance in terms of reproducibility and robustness. The room temperature chemistry utilized to form the entrapped column enables the column to be photopatterned anywhere within the capillary without loss in bead functionality, and effectively links individual beads to one another at specific bead-bead and bead-capillary contact points. A 0.5 cm long entrapped bed exhibits high mechanical strength and is able to withstand >4400 psi. The entrapped bed was used to preconcentrate progesterone and beta-estradiol providing signal enhancements of >600. Following preconcentration, the hormones could be separated using CEC. With the current availability of numerous well-characterized chromatographic packing materials and the relative simplicity of the fabrication method, this methodology can be readily adapted to HPLC, CEC, and micro total analysis system.

Entrapment of functionalized silica microspheres with photo-initiated acrylate-based polymers

“…The columns have exceptional stability yet no interfering interstitial polymer formation, allowing lower back pressures while maintaining access to the microspheres. Our group has already demonstrated the utility of this type of material [26][27][28]. The novel entrapment procedures presented in this work can be utilized to encapsulate a bed of hydrophobic microspheres, though the general approach can be easily adapted to a variety of other types of particles.…”

In‐capillary preconcentration of pirimicarb and carbendazim with a monolithic polymeric sorbent prior to separation by CZE

“…There are different ways in which SPE can be integrated with CE: off‐, at‐, on‐, and in‐line 16. The best integration can be achieved with in‐line coupling of SPE with CE, in which the preconcentration sorbent is placed directly inside the electrophoretic separation capillary 19–21. In this mode, once preconcentration has been performed, the amount eluted is subjected to electrophoretic separation.…”

Surface-mediated effects on porous polymer monolith formation within capillaries

“…The formulation for the porous polymer monolith is similar to that described in our previous papers [11,[26][27][28]. The polymerization mixture is composed of 67% porogenic solvent (60% acetonitrile, 20% ethanol (95%) and 20% potassium phosphate buffer (5 mM, pH -6.7)), 23% butyl acrylate, 10% 1,3-butanediol diacrylate, and 6.8-6.9 mg AIBN.…”