Retention and selectivity tests of silica‐based and metal‐oxide bonded stationary phases for RP‐HPLC

Abstract

Chromatographic properties of silica-, zirconia- and alumina-based columns with octadecyl-, polyethylene glycol- and pentafluorophenylpropyl-bonded stationary phases were tested. Selectivities of nine columns for LC were characterized using chromatographic methods including Walters, Engelhardt, Tanaka and Galushko hydrophobicity and silanol activity tests, measurements of methylene selectivity in various aqueous-methanol and aqueous-acetonitrile mobile phases and of gradient lipophilic capacity as a measure of the effect of the sample hydrophobicity on gradient-elution separations. A semi-empirical interaction indices model, assuming a predominant role of the solvophobic interactions of test compounds with different polarities, was compared with the linear free energy relationships approach taking into account selective polar interactions. The interaction indices model was applied to both non-polar stationary phases bonded on silica, alumina and zirconia supports, and to the non-modified adsorbents in the normal-phase LC. The retention data of isomeric naphthalene disulfonic acids were used to compare the attractive and repulsive ionic interactions of the columns in purely aqueous mobile phases. The results of the hydrophobicity and polarity tests were consistent, and allowed column characterization and classification. Silanol activity was important with octadecyl silica columns, but was relatively insignificant with bonded polyethylene glycol and pentafluorophenylpropyl phases on silica gel support. Polar interactions with the alumina and zirconia support materials significantly affect the retention.

Investigation on performance of zirconia and magnesia–zirconia stationary phases in hydrophilic interaction chromatography

“…However, it is well known that the native SiO 2 can endure the MP pH o 8.0 [3,11], and hence pH of within the range of 3.0-7.5 was studied on SiO 2 column. Fig.…”

“…An increasing number of reports [18][19][20]25,[27][28][29]31,[33][34][35][36][37] on thermodynamics in HILIC were found in recent years, which provided necessary theory guidance when column temperature was used as a variant regulating selectivity and analysis speed. In RPLC and NPLC mode for high temperature separations, metallic oxides such as TiO 2 or ZrO 2 -based columns were used, which were reported to be stable up to 200 1C [1][2][3]. High column temperature offered lower back column pressure [31], shorter analysis time and higher column efficiency [33,37].…”

“…Zirconium dioxide (zirconia, ZrO 2 ), thanks to its remarkable thermal stability (can withstand high temperature up to 200 1C in chromatographic separation [1][2][3]), pH stability in the range of 1-14, mechanical stability as well as its particular surface chemical properties, has become one of the alternative metallic oxide-based chromatographic stationary phases (SPs) to silica (SiO 2 ) [4,5]. The surface of ZrO 2 is far more intricate than that of native SiO 2 , containing a number of distinct classes of interaction sites including Brönsted acid, Brönsted base and Lewis acid sites [6].…”

Characterization of HPLC columns for two‐dimensional LC × LC separations of phenolic acids and flavonoids

“…The test methods can be widely applied to all types of LC columns based on silica gel, metal oxide or organic polymer supports [5,6].…”

Stationary phase characterization and method development

“…More recently, Jandera et al [116] compared six very different columns using several different popular column tests, including the method just described, and the Engelhardt [5], Galushko [117], Tanaka [31], and Walters [118] tests. Also, Jandera's test for methylene-group selectivity was used for a subset of the columns together with the method of interaction indices [119,120].…”