Deuterium nuclear magnetic resonance spectroscopy as a probe for reversed-phase liquid chromatographic bonded phase solvation. 2. Aqueous solvation in methanol and acetonitrile binary mobile phases

Abstract

Using the inversion/recovery method, deuterium (2H) longitudinal relaxation times, (TO, of deuterium oxide were measured for binary solutions of methanol and D20 and acetonitrile and D20 and for these mixtures in contact with two different reversed-phase liquid chromatographic stationary phases. Changes in the D20 Ti for the solutions in contact with the stationary phase compared to those observed for the solutions alone give a qualitative understanding of the degree of association of water with the stationary phase. The results for two stationary phases with greatly different Ci8-bonding densities are reported and discussed. The results are also compared and contrasted to our previous work, which examined changes in 2H T\ for deuterated methanol and acetonitrile in the same binary hydroorganic solutions as well as for these mixtures in contact with the same two stationary phases.

Investigating the Location of Propyl Gallate at Surfaces and Its Chemical Microenvironment by 1H NMR

“…The portion of PG that is solubilized in the different micelles (f sol ) was determined by ultra filtration method described by Stöckmann and Schwarz [2] and found in CTAB micelles of about 0.989, in Brij micelles of about 0.893, and in SDS micelles of about 0.735. Provided that the free mobility is the same for the portion of PG in the aqueous phase of the micellar solution as for PG in buffer solution T 1,sol the relaxation rate for PG solubilized in the micellar phase (T 1,eff ) was calculated by [41][42][43][44][45] 1…”

Chromatographic activity of residual silanols of alkylsilane derivatized silica surfaces

“…The retention of DETA is sensitive towards silanol activity, while anthracene retention behavior is assumed to be solely determined by hydrophobic interactions. The use of 100% acetonitrile as mobile phase may be advantageous to our purpose, as acetonitrile solvates C18 alkyl chains rather well [33,34]. Solvation of the alkylsilane layer is assumed to facilitate access of solutes to residual silanol sites [11] and therefore eluents with a high acetonitrile content will show a RP-column's worst behavior towards basic analytes.…”

Evaluation of column characteristics in RPLC using linear solvation energy relationships (LSERs)

“…Firstly, spectroscopic studies have shown distinctly different reversed-phase solvation characteristics of methanol-water compared with acetonitrilewater. Increased solvation of the bonded ligands in the latter mobile phase may allow greater penetration of components to the silanols [83,84]. Recent studies of the excess adsorption of eluent components on RP phases suggest that acetonitrile molecule interact mostly with the alkyl groups of the bonded phases with negligible influence on residual silanol groups [85] and the silanols may be more available for interaction with the solutes [86].…”

“…the extent of polar interactions between the stationary phase and the solutes, decreases considerably with increasing water content, that is increasing polarity of the mobile phase. The explanation of this phenomenon is that by increasing polarity of the mobile phase the polar sites on the stationary phase are more and more masked and are less available for polar interactions [83,84,85,86]. Comparing the two Figures it can be seen that the secondary interactions, the polar properties of the stationary phase are significantly more suppressed with methanol than with acetonitrile, resulting in smaller polar selectivity factors.…”