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R E Waltermire

Publications and source records attributed to R E Waltermire.

3 recordsLinked to original sources
PubMed2001

The role of modifiers in high selectivity chiral separations on Pirkle-type columns.

Atypically high selectivity (alpha > 2) chiral separations have been observed on Pirkle type supports. These separations were examined in terms of their response to various modifiers, thermodynamic behavior and LSER modeling. Atypical thermodynamic and LSER results were observed along with large changes in selectivity between modifiers. The use of bulky modifiers gave increased selectivity resulting from dramatic increases in the retention of the second eluting enantiomer. These findings lead to the conclusion that increased retention is due to an inability of bulky modifers to penetrate a tight complex between selector and this enantiomer.

Journal Article↗
PubMed1999

Empirical relationship between chiral selectivity and mobile phase modifier properties.

An empirical relationship was derived which relates properties of the mobile phase modifier to the chiral selectivity factor for a given analyte/chiral selector combination. Using carbon dioxide and heptane-based mobile phases, the effect of various mobile phase modifiers on Pirkle-type stationary phases may be accurately modeled using a two-parameter equation. Similar results are obtained using cellulosic stationary phases with carbon dioxide-based mobile phases. Modeling separations performed using heptane-based mobile phases with cellulosic stationary phases were not successful. The predictive ability of this modeling approach was demonstrated using novel modifiers and chiral analytes.

Chromatography, Liquid↗