many modern analytical methods deal with the trace-level determination of compounds of interest in highly complex environmental samples by means of chromatographic techniques. the introduction of a “clean” sample into an analytical instrument can make analyses easier and prolongs the equipment life. the use of solid-phase extraction (spe) has grown and is a fertile technique of sample preparati...

Silica-bonded N-propyldiethylenetriamine (7) is employed as a recyclable heterogeneous solid base catalyst for the synthesis of 2-amino-3,5-dicarbonitrile-6-thiopyridines through pseudo four-component condensation reaction between aromatic aldehydes, malononitrile, and 2-amino-thiophenol in refluxing ethanol. Silica-bonded N-propyldiethylenetriamine showed much the same efficiency when used in ...

silica-bonded n-propyldiethylenetriamine (7) is employed as a recyclable heterogeneous solid base catalyst for the synthesis of 2-amino-3,5-dicarbonitrile-6-thiopyridines through pseudo four-component condensation reaction between aromatic aldehydes, malononitrile, and 2-amino-thiophenol in refluxing ethanol. silica-bonded n-propyldiethylenetriamine showed much the same efficiency when used in ...

The goal of this study was to define practical conditions and limitations of using silica-based, endcapped bonded-phase columns in intermediate and higher pH environments for developing rugged HPLC methods. Bonded-phase degradation in this pH range is a result mainly of silica support dissolution; covalently-bound silane ligands are hydrolyzed very slowly if at all from silica supports at inter...

silica-bonded n-propyltriethylene-tetramine (sbnptt) was found as an efficient solid base for the synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4h-chromenes. chromene derivatives were obtained via the three-component condensation reaction of aromatic aldehydes, malononitrile, and dimedone at 80 oc under solvent-free conditions. the heterogeneous solid base showed much the same efficiency when u...

The authors describe the preparation of a C18 bonded phase using silica chemically modified with tetraisopropyl orthotitanate. The product was reacted with ocadecyltrimethoxysilane to yield a reversed phase. The chromatographic performance of this phase was evaluated for the separation of various test mixtures containing polar, nonpolar, and basic compounds, and its stability at pH 9 and 10 was...

Bonded optically active tripeptides have been applied as stationary phases for liquid chromatography. Significant retention variations are shown for some UV absorbing amino acids when compared to a silica gel column using the same mobile phase. The separation of certain isomeric dipeptides has been accomplished using the bonded optically active tripeptide stationary phases. It is shown that th...

Chromatography is a tool to measure molecular interactions, and computational chemistry is a tool to explain molecular interactions. Therefore, reversed-phase liquid chromatography of acidic drugs using a pentyland an octyl-bonded silica gels was quantitatively analyzed in silico. A model pentyland an octyl-bonded silica gel and a methanol phases were constructed for docking with acidic drugs. ...

In this study, solid-phase microextraction fibers coated with modified silica particles (5 pm dp) bonded to methyl (C1), hexyl (C6), octyl (C8), and polymeric octadecyl (C18) groups are prepared and evaluated. Selective extraction of polycyclic aromatic hydrocarbons (PAHs) from river water is used to demonstrate the selective behavior of the fibers as a function of the alkyl chains bonded to th...

Ion irradiation is an alternative to heat treatment for transforming organic-inorganic thin films to a ceramic state. One major shortcoming in previous studies of ion-irradiated films is the assumption that constituent phases in ion-irradiated and heat-treated films are identical and that the ion irradiation effect is limited to changes in composition. In this study, we investigate the effects ...