No abstract

A novel fritless capillary column for capillary electrochromatography (CEC) has been developed. The ODS microspheres were packed into a capillary and were then immobilized within an organic polymer prepared in situ through a photopolymerization process. The entrapment conditions were investigated to minimize the effect of the polymer matrix on the chromatographic properties of the packing material. The organic polymer matrix in the microsphere-packed column functions to link microspheres at specific sphere-sphere and sphere-capillary contact points. CEC separations of a PAH test mixture using entrapped columns with different UV illumination times were compared in terms of retention factor and separation efficiency. The optimized entrapped column demonstrated better chromatographic performance than similarly packed columns with conventional inlet and outlet frits. The electrochromatographic separations of hormones and peptides were also demonstrated on entrapped ODS columns.

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.

No abstract

In this study a nano-electrospray emitter is constructed by precisely positioning entrapped octadecylsilane (ODS) particles within a photoinitiated polymer at the exit aperture of a capillary. Following poly-merization, the microsphere/polymer hybrid material is able to withstand pressures greater than 4000 psi for 1 cm length of material. Smaller microspheres (3 microm) patterned at the exit aperture of a capillary generated the most sensitive/stable electrospray from 100 to 1000 nL/min and moderately stable signal under 100 nL/min. Constant infusion of a standard PPG solution from a batch of eleven emitters resulted in a relatively small variance in total ion current (TIC) counts (8%). The entrapped microsphere emitter design yields an emitter that minimizes clogging and eliminates dead volume between the chromatographic bed and the electrospray emitter. The entrapped ODS microspheres can also be used for sample preparation prior to mass spectrometry (MS) analysis. We show the solid-phase extraction and preconcentration of 20-700 fmol of a peptide (leucine enkephalin) prior to MS analysis on an emitter with 1 cm of entrapped microspheres.