Histidine-modified organic-silica hybrid monolithic column for mixed-mode per aqueous and ion-exchange capillary electrochromatography

Abstract

A novel organic-silica hybrid monolith was prepared through the binding of histidine onto the surface of monolithic matrix for mixed-mode per aqueous and ion-exchange capillary electrochromatography. The imidazolium and amino groups on the surface of the monolithic stationary phase were used to generate an anodic electro-osmotic flow as well as to provide electrostatic interaction sites for the charged compounds at low pH. Typical per aqueous chromatographic behavior was observed in water-rich mobile phases. Various polar and hydrophilic analytes were selected to evaluate the characteristics and chromatographic performance of the obtained monolith. Under per aqueous conditions, the mixed-mode mechanism of hydrophobic and ion-exchange interactions was observed and the resultant monolithic column proved to be very versatile for the efficient separations of these polar and hydrophilic compounds (including amides, nucleosides and nucleotide bases, benzoic acid derivatives, and amino acids) in highly aqueous mobile phases. The successful applications suggested that the histidine-modified organic-silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar and hydrophilic compounds.

Direct and simultaneous determination of methionine sulfoxide and pyroglutamic acid impurities in Compound Amino Acid Injection‐18 AA by ion‐pair reversed‐phase HPLC

“…Previous reports described the successful use of sodium 1‐heptanesulfonate as ion‐pairing agent for the separation of many drugs . Due to the ionizable nature of free amino acids (cationic, anionic or even zwitterionic), their separation can also be achieved by ion‐exchange or ion‐pair RP HPLC . In ion‐pair RP HPLC, the separation of amino acid ionic compounds can be improved by adding ion‐pairing reagents to the mobile phase, which can enhance their retention.…”

Preparation of a polyhedral oligomeric silsesquioxanes hybrid monolith via a single‐step ring‐opening polymerization for pressurized capillary electrochromatography

“…It was observed that a mixture of toluene, DMF, acrylamide, and thiourea was baseline separated successfully with good peak shapes under the mobile phase of 80% (v/v) ACN/HAc–NaAc (Fig. A), and they were eluted according to their polarity in order from low to high, which was consistent with the hydrophilic interaction (HI) mechanism . The effect of ACN content on the retention factors ( k´ ) was investigated by using different ACN contents from 50 to 90% (v/v) in the mobile phase.…”

Advances in the development and applications of organic–silica hybrid monoliths

“…Rapid developments have been noticed with mixed‐mode organic–silica monoliths as they allow for more than one kind of separation capability using one single column. Among these are columns prepared from TMOS and 3‐chloropopyltrimethoxysilane (CPTMS) functionalized by nucleophilic substitution reactions with tertiary amines such as 4,5‐imidazoledicarboxylic acid , imidazole‐1‐acetic acid , 4,4’‐dipyridyl , o ‐phenanthroline , or histidine . For analysis of wide range of compounds these columns exhibited multiple retention mechanisms such as hydrophobic, hydrophilic, π–π and ion‐exchange interactions in reversed‐phase and per aqueous CEC.…”