Analysis of toxic anthraquinones and related compounds with a fused silica capillary column

In this study, application of a fused silica capillary column for analysis of toxic anthraquinones and related compounds found in plants was investigated.     

Analysis of mutagenic amino acid pyrolyzates with a fused silica capillary column

In this study, application of a fused silica capillary column for analysis of major mutagenic heterocyclic compounds found in cooked foods was investigated.     

An application of factorial design to the development of fused silica capillary columns

Stationary phase crosslinking conditions for fused silica capillary columns were optimized with the use of a factorial design experiment. This experimental strategy was chosen because it provided for the determination of two-factor interactions. A predictive model was developed for the desired chromatographic performance parameters as a function of the variables of the crosslinking reaction. Confirmatory experiments proved the usefulness of the mathematical model which resulted in the production of capillary columns of superior performance with significant improvements in reproducibility.     

Characterization of glass,quartz, and fused silica capillary column surfaces from contact-angle measurements

Summary This paper describes the systematic characterization of glass and the newly introduced fused silica and quartz capillary columns from surface wettability measurements. Common gas chromatographic stationary phases were used in capillary-rise measurements at temperatures up to 300°C. By construction of Zisman plots and using the Cassie equation, the relative surface concentrations of wettable and non-wettable groups were determined. By application of the Fowkes equation, the dispersion force component of the surface energy was investigated. The influence of various surface treatments such as leaching, silylation, and polymeric film formation are discussed. Wettability measurements were also used to evaluate the thermostability of various treated surfaces and to compare the surface properties of glass, quartz, and fused silica. The wettability of the surfaces with selected stationary phases as a function of temperature is also discussed.     

Deactivation of fused silica capillary columns with cyanopropylhydrosiloxanes

A method is described for surface deactivation and modification of fused silica capillary columns with a cyanopropyl-containing reagent. The deactivation procedure involved a dehydrocondensation reaction between a bis(cyanopropyl)methylhydropolysiloxane reagent and surface silanol groups at an optimum temperature of only 250°C. Actual critical surface tension measurements were made using the capillary rise method. Excellent deactivation for acidic and basic compounds at the low ng level, and wettability for nonpolar and polar polysiloxane stationary phases were obtained. A procedure was developed to remove acidic impurities that are present in polar stationary phases.     

Loss of water during heat treatment of acid leached glass and fused silica capillary columns

A study was carried out on the effects of acid leaching of capillary column wall materials. Leaching experiments with glass and fused silica were performed under static and dynamic conditions; moreover, the influence of the temperature was investigated. The amount of water released during different temperature programs was measured with a microwave plasma detector. Different leaching conditions and column wall materials cause considerable variations in water production. These results probably explain the disappointing deactivation efficiency obtained for fused silica and dynamically leached soft glass if HMDS is used. Evidence was found for an increase in surface area due to acid leaching.     

Deactivation of fused silica capillary columns with phenylhydrosiloxanes

In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation and surface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using the capillary rise method. The deactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.     

Hydrothermal treatment of fused silica capillary columns

The activity of fused silica capillary tubing has been shown to vary considerably, which severely influences the reproducibility of column deactivation and inertness. Methods for producing a reproducible, high activity surface with maximum hydroxylation by various hydrothermal treatments were evaluated. Columns pretreated with 20% nitric acid at 200°C for 10 hours, deactivated with D₄, coated with OV-73, and crosslinked with azo-tert-butane were found to possess excellent inertness for sensitive analytes such as alcohols, amines, and alkaloid drugs.     

On the stability of micro-LC columns (packed fused silica capillary columns)

The life expectancy and resistance to flow, pressure shocks, solvent gradients, and bending of packed fused silica capillary columns (Micro-LC) are discussed.     

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

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.