Retention behavior on alkyl bonded stationary phases in liquid chromatography

Abstract

The retention behavior on alkyl bonded stationary phases for liquid chromatography has been studied as a function of chain length, surface coverage, solute type, mobile phase composition, and temperature. The data indicate that depending on the degree of surface coverage and the type of solute, mixed mechanisms may play an important part in the retention behavior. Efficiencies and capacity ratios show an Increase as the bonded phase loading increases while asymmetry shows a decrease. Using a nonpolar mobile phase AH shows an odd-even effect as a function of the carbon number of the alkyl side chain in phenones. In a polar mobile phase AH seems to determine retention order except for the case of a heavily loaded column. In general, the data Indicate that alkyl bonded phase columns are most useful when the amount of bonded stationary phase Is maximized.(Jnabated interest has continued in the development of permanently bonded stationary phases for liquid chromatography. Though many such bonded phases continue to be prepared and applied to a great variety of separation problems with a high degree of success, few studies have been directed at providing a mechanistic description of their operation. Recent reviews (1-3) have aptly covered the current uses of bonded stationary phases in liquid chromatography. In a previous paper we have presented a detailed study on a polar bonded phase prepared by reacting Corasil II with 1-trimethoxysilylchloromethylphenylethane (4). Novotny and his co-workers (5) started with a similar material, but proceeded to hydrolyze the terminal chlorine to a hydroxyl group before studying its properties. Knox and Vasvari's (6) work on polymeric bonded phases presents one of the first systematic approaches of studying retention mechanism in bonded phases.Although much remains to be learned about the behavior of bonded phase systems, useful information has already been determined. Kirkland (7) has found that with polymeric phases adsorption on the polymer and interaction with stagnant pockets of mobile phases are important in determining chromatographic parameters. Little and his co-workers (8) have shown that in brush systems residual silanol groups play an important part in the separations. There are reasons to believe that this also holds true for liquid chromatographic systems.Karger and Sibley (9) have shown that in gas chromatography, when employing a nonpolar bonded brush system, the type of bonded phase determines the retention characteristics of the system. A recent study by Majors and Hopper (10) suggests that in reverse phase systems the retention increases as the length of the bonded phase increases. They did not find, however, a correlation between surface coverage and retention time. Locke (11) has demonstrated that the retention order, in reverse phase chromatography, is a function of the solutes solubilities in the mobile phase. In a study of in situ bonded stationary phases, Gilpin and his co-workers (12) have shown that increasing the length of the bonded phase from ethyl to oct...

Evidence for solute-brush interactions on nonpolar chemically bonded stationary phases in gas chromatography

“…Mass spectra (23 eV, emission 30 µ ) were recorded with a JMS-100 (Jeol, Japan) instrument equipped with a JGC-20K gas chromatograph. For MS measurements the SP-2340 column was used and the separation was carried out under identical conditions except that helium, at inlet pressure 98.1 kPa, was used as a carrier gas.…”

“…Many researchers have investigated the separating abilities and efficiencies of some bonded phases (2,3,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Much of this work has been done in high pressure liquid chromatography (9,10,13,19,21,23).…”

“…Many researchers have investigated the separating abilities and efficiencies of some bonded phases (2,3,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23). Much of this work has been done in high pressure liquid chromatography (9,10,13,19,21,23). Although bonded phases may be structurally identical in gas and liquid chromatography, differences in properties exist due to mobile phase solvation in HPLC.…”

Multi-step derivatization and analysis of the surface of nonporous silicate glass

“…For example, they have been used to tailor silica support materials in the field of chromatography [2][3][4][5][6][7]. When the -R group itself has not provided the specific adsorption characteristics needed, further derivatization of the -R group has been conducted to achieve the desired adsorption characteristics [8,9].…”

Temperature Effects on Retention in Reversed-phase Liquid Chromatography of Nucleosides and Their Bases Using Water as the Mobile Phase

“…The hydrophobicity and the morphology of ODS stationary phases are known to be extremely dependent on the temperature [7][8][9][10][11][12][13][14] and a variation in the temperature can result in altered retention times, separation efficiencies, and/or separation selectivities. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] In other words, a change in temperature can result in variation of the properties of an RP-LC system.…”