A study of surface modification and anchoring techniques used in the preparation of monolithic microcolumns in fused silica capillaries

Abstract

Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3-((trimethoxysilyl)propyl) methacrylate (gamma-MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6-butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.

A Phosphotyrosine‐Imprinted Polymer Receptor for the Recognition of Tyrosine Phosphorylated Peptides

“…[ 17] The capillaries were washed with acetone and deionized water, flushed for approximately 5 min with 1 m aqueous NaOH, sealed in the filled state, etched by heating in a circulating air oven at 120 8C for 2 h, and cooled to room temperature. A washing procedure of deionized water and acetone (15 min each in sequence) was employed and the final drying took place in a vacuum oven at 60 8C for at least 1 h. A silanization reaction to introduce methacrylic anchoring groups onto the surface was carried out by filling the capillary with a mixture of g-MAPS in DMF (1:1, v/v) containing 0.01 % DPPH.…”

Preparation and application of monolithic beds in the separation of selected natural biologically important compounds

“…We noticed that different silanization procedures led to differences in mechanical stability of the monolith, meaning that "bad" silanization can lead to local inhomogeneities of the monolithic stationary phase and unpredictable behavior of the capillary column. This issue was the subject of an extended study by Courtois et al [63] who compared three methods of etching and eleven methods of silanization, which were chosen as the most representative of those that can be found in the literature. Evaluation of the etching and silanization steps was performed by X-ray photoelectron spectroscopy (XPS), results of which were correlated with wetting angle measurements.…”

New fractionation tools targeting elusive post-translational modifications

“…This high energy phosphoramidate bond is susceptible to hydrolysis in acidic environment and it defines unique stability profile of phosphohistidine. 29,30 Figure 3. Structures of π-phosphohistidine, τ-phosphohistidine and π, τ-diphosphohistidine.…”

“…To date, several methods for detection and analysis of pHis have been reported. 17,29,30 Generation of synthetic pHis proteins and peptides has clearly facilitated the development of such methods. Medzihradszky et al 31 used potassium phosphoramidate to synthesize histidine phosphorylated peptides.…”

“…29 with the procedure being selected on the basis of a previous study. 30 Briefly, the capillaries were washed with acetone and deionized water, then 1 M NaOH was flushed through the capillary for approx. 5 min, where after the capillary was sealed in the filled state.…”