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Chaotropic salts: Novel modifiers for the capillary electrophoretic analysis of benzodiazepines
Author(s) -
Su HsiuLi,
Lan MinTsu,
Lin KuanWen,
Hsieh YouZung
Publication year - 2008
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200800073
Subject(s) - chaotropic agent , chemistry , lithium (medication) , hexafluorophosphate , imide , ion , trifluoromethanesulfonate , inorganic chemistry , chromatography , organic chemistry , ionic liquid , medicine , endocrinology , catalysis
This paper describes a CE method for analyzing benzodiazepines using the chaotropic salts lithium trifluoromethanesulfonate (LiOTf), lithium hexafluorophosphate (LiPF 6 ), and lithium bis(trifluoromethanesulfonyl)imide (LiNTf 2 ) as modifiers in the running buffer. Although adequate resolution of seven benzodiazepine analytes occurred under the influence of each of the chaotropic anions, the separation efficiency was highest when bis(trifluoromethanesulfonyl)imide (Tf 2 N − ) was the modifier. We applied affinity CE in conjunction with linear analysis to determine the association constants for the formation of complexes between the Tf 2 N − anion and the benzodiazepines. According to the estimated Gibbs free energies, the interactions between this chaotropic anion and the benzodiazepines were either ion–dipole or ion–induced dipole interactions. Adding chaotropic salts as modifiers into CE buffers is a simple and reproducible technique for separating benzodiazepines.