Search results for "Capillary electrochromatography"

Surface initiated molecularly imprinted polymer films: a new approach in chiral capillary electrochromatography

2001

A new generation of imprinted composite particles was tested as capillary electrochromatography stationary phase. Silica particles characterised by a well defined particle size (10 µm diameter), shape and pore system (1000 A) were modified with an azoinitiator and subsequently used to graft molecularly imprinted polymers targeted to bind L-phenylalanine anilide. Fused silica capillaries were packed over a length corresponding to 8 cm, using a pneumatic amplification pump, and the stationary phase thus obtained was tested with respect to its electrochromatographic performance. The electroendosmotic flow mobility was evaluated with respect to both the different content of polymer on the silic…

Poly(ethylene glycol) diacrylate based monolithic capillary columns for the analysis of polar small solutes by capillary electrochromatography

2018

Monolithic stationary phases based on poly(ethylene glycol) diacrylates for capillary electrochromatography were developed. Several poly(ethylene glycol) diacrylates (Mn 250, 575, and 700) were used as single monomers and the resulting columns were carefully compared. Methanol and ethyl ether were selected as porogenic solvents, and in all cases ultraviolet radiation was selected as initiation method to prepare polymeric monoliths. The influence of the monomer chain length and ratio monomer/porogen on the morphological and electrochromatographic properties of the resulting monoliths was investigated. Several families of compounds with different polarity (alkyl benzenes, organophosphorous pe…

Life-time studies with capillary electrochromatography columns operated under different conditions.

2000

A test system has been established to permit the monitoring of the life-time performance of several reversed- phase capillary electrochromatography (CEC) columns. The retention factors, k(cec), peak symmetry coefficients, lambda(sym), and column efficiencies, N, of three neutral n-alkylbenzene analytes, namely ethyl-, n-butyl- and n-pentylbenzenes, were determined for Hypersil 3 microm n-octylsilica and n-octadecylsilica packed into CEC capillary columns of 100 microm I.D., with a packed length of 250 mm, and a total length of 335 mm. The performances of these CEC capillary columns were examined for a variety of eluents with pH values ranging between pH 2.0 - 8.0, similar to those employed …

Hybrid methacrylate monolithic columns containing magnetic nanoparticles for capillary electrochromatography

2015

Abstract Vinylized iron oxide magnetic nanoparticles (VMNPs) were incorporated into polymethacrylate monolithic columns to develop novel stationary phases with enhanced separation performance. The VMNPs were dispersed in a polymerization mixture containing gycidyl methacrylate and ethylene glycol dimethacrylate as monomers, cyclohexanol and 1-dodecanol as porogens and azobisisobutyronitrile as initiator. The stability of the VMNPs in the polymerization mixture was investigated at several VMNP contents. Using short UV-polymerization times, polymeric beds with homogenously dispersed VMNPs were obtained. The novel stationary phases were characterized by scanning electron microscopy. The chroma…

Capillary electrochromatography analysis of hormonal cyclic and linear peptides.

2001

The retention behavior of linear and cyclic peptides has been studied by capillary electrochromatography (CEC) with a variety of different n-alkyl silica reversed-phase sorbents and also with mixed-mode phases containing both strong cation-exchange (sulfonic acid) and n-alkyl groups bonded onto the silica surface, using eluents ranging from pH 2.0 to pH 5.0. Depending upon the amino acid sequence, electrochromatographic retention of the peptides was strongly affected by the composition of the eluent, its pH value, and the choice of sorbent packed into the capillaries. The dominant separation processes operating with these charged analytes could be modulated inter alia by the content of orga…

Study of peak shape and efficiency in butyl acrylate-based monolithic columns for capillary electrochromatography.

2009

Abstract The study and modelling peak shape of in capillary electrochromatography (CEC), obtained using butyl acrylate (BA)-based monolithic columns, is described in this article. A modified-Gaussian model, which is a function of conventional experimental parameters: retention time (tR), peak height (H0) and standard deviation (σ0) at the peak maximum, and left (A) and right (B) halfwidths, was used to describe the peaks of thiourea and several polyaromatic hydrocarbons compounds, which were eluted under several applied voltages. A mean relative error below 2% in the prediction of peak shape is obtained. Based on peak parameters, an easy and reliable estimation of global chromatographic per…

The CEC behaviour of several synthetic peptides related to the activin ��A-��D subunits

2008

The resolution of several structurally related synthetic peptides, derived from the loop 3 region of the activin betaA-betaD subunits, has been studied using capillary electrochromatography (CEC) with Hypersil n-octadecylsilica as the sorbent. The results confirm that the CEC migration of these peptides can be varied in a charge-state-specific manner as the properties of the background electrolyte, such as pH, salt concentration and content of organic modifier, or temperature are systematically changed. Acidic peptides followed similar trends in retention behaviour, which was distinctly different to that shown by more basic peptides. The CEC separation of these peptides with the Hypersil n-…

Calixarenes as Stationary Phases

2006

Methacrylate monolithic columns functionalized with epinephrine for capillary electrochromatography applications.

2013

Epinephrine-bonded polymeric monoliths for capillary electrochromatography (CEC) were developed by nucleophilic substitution reaction of epoxide groups of poly(glycidyl-methacrylate-co-ethylenedimethacrylate) (poly(GMA-co-EDMA)) monoliths using epinephrine as nucleophilic reagent. The ring opening reaction under dynamic conditions was optimized. Successful chemical modification of the monolith surface was ascertained by in situ Raman spectroscopy characterization. In addition, the amount of epinephrine groups that was bound to the monolith surface was evaluated by oxidation of the catechol groups with Ce(IV), followed by spectrophotometric measurement of unreacted Ce(IV). About 9% of all th…

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

2008

The preparation of lauryl methacrylate (LMA)-based monolithic columns for CEC using lauroyl peroxide (LPO) as thermal initiator of polymerization has been investigated. The influence of initiator amount and composition of porogenic solvent on the physical and electrochromatographic properties of the resulting LMA-based monoliths was evaluated. A comparison with LMA-based columns thermally polymerized with AIBN was performed. At a given porogenic solvent composition, LMA stationary phases initiated with LPO showed higher permeabilities and better efficiency values than those prepared using AIBN as initiator. The optimum polymerization mixture found for LPO initiator provided a minimum plate …