Separation of Amino Acids by High Performance Liquid Chromatography Based on Calixarene-Bonded Stationary Phases

Abstract

In this work, we present a new method for synthesis of silica gel stationary phases based on calix[4]arene derivatives. In order to achieve it, 25,27-dipropoxy-26,28-bis-[3-propyloxydimethylsililoxy]calix[4]arene has been synthesized in six steps and immobilized on silica via chlorotrimethylsilane. Stationary phases were characterized by elemental analysis, infrared spectroscopy and thermal analysis and used for the separation of amino acid derivatives by high performance liquid chromatography. The effect of isocratic and gradient elution, pH and column temperature on retention and selectivity of the Fmoc-protected amino acids were studied. The retention mechanism was also discussed. The results indicated that the stationary phase behaves like a reverse phase packing. Size exclusion, electron-π, π-π and hydrophobic interactions seem to be involved in the separation process.

Synthesis of Bromoundecyl Resorc[4]arenes and Applications of the Cone Stereoisomer as Selector for Liquid Chromatography

“…Thus, the surface linking of the resorc[4]­arene was first confirmed by the appearance of FT-IR bands at 1735, 1612, and 1506 cm –1 (see Figure S2 of the Supporting Information). Afterward, elemental analysis of the final SP-C 11 -resorc­[4]­arene stationary phase (see Table ) gave a resorc[4]­arene loading equal to 0.28 μmol/m 2 (based on the carbon content), which is comparable with the coverage data obtained in the literature for the surface linking of calix­[ n ]­arenes ( n = 4, 6, 8) and resorcinarenes, albeit featuring different functionalities. − Finally, based on the bromine content found on the phase, we can state that about two over four arms has statistically been attached to the aminopropylated silica gel. The SP-C 11 -resorc­[4]­arene stationary phase obtained was packed into a stainless-steel column (250 × 4.0 mm i.d.)…”

“…We became interested in developing a stationary phase for HPLC capable of discriminating the E / Z stereoisomers of combretastatins, and we planned to combine the entrapping properties of functionalized resorc[4]­arenes with a suitable anchorage to a solid support . Notably, whereas many calixarene-based stationary phases have been developed for HPLC applications, − the resorc[4]­arene scaffold was much less investigated as a selector for liquid chromatography. , Enantiomerically pure resorcinarenes have indeed been employed as selectors of chiral stationary phases (CSPs) for gas chromatography. , …”

Preparation and evaluation of a chiral HPLC stationary phase based on cone calix[4]arene functionalized at the upper rim with l‐alanine units

“…For these reasons, some functionalized calix[n]arenes have been synthesized and their applications have been reported in a variety of chromatography fields, for example gas chromatography (Delahousse et al, ; Fan et al, ; Yu, Fang, Lin, Han, & Wu, ), capillary electrophoresis (Wang, Chen, Yuan, Huang, & Liu, ; Yang, Yu, Yu, & Chen, ; Zhou, Li, & Zeng, ), capillary electrokinetic chromatography (Hamilton, ) and liquid chromatography (Barc & Śliwka‐Kaszyńska, ; Deng et al, ; Erdemir & Yilmaz, ; Hu et al, ; Lu et al, ; Śliwka‐Kaszyńska & Ślebioda, ). Recently, we have introduced a stationary phase, based on calix[4]arene derivative for the separation of Fmoc‐protected amino acids (Zadmard, Tabar‐Heydar, & Imani, ).…”