The antagonistic role of chaotropic hexafluorophosphate anions and imidazolium cations composing ionic liquids applied as phase additives in the separation of tri-cyclic antidepressants

Magda Caban , Piotr Stepnowski


The main advantage of alkylimidazolium cation-based ionic liquids (ILs) as phase additives in RP-HPLC is believed to be the suppression of deleterious residual free silanols in chemically modified silica stationary phases. However, up to now, the influence of ILs was usually evaluated having in mind a particular IL salt as one compound, not as a specific mixture of cations and anions. This in fact led to some misinterpretation of observed results, very often related to the suppression effect, while in fact caused by the nature of IL anions, which contribute to the elevated chaotropicity of the separation phases.In the present study, we have attempted to consider the effect gained due to the presence of both ionic liquid entities in the mobile phase used for the separation of basic compounds. Tri-cyclic antidepressants (TCAs) were taken as representative analytes. The effect of ILs on the chromatographic separation of TCAs was investigated in comparison to common mobile phase additives and by the presentation of retention factors, tailing factors and theoretical plates. In addition, an overloading study was performed for the IL-based phases for the first time. In general, it was found that the effect of chaotropic hexafluorophosphate anions in ILs is much stronger and opposite to that caused by imidazolium cations. The overloading study gives interesting information on how imidazolium cations affect the separation of cationic analytes. Finally, the usefulness of imidazolium-based ILs as mobile phase modifiers in the RP-HPLC separation of basic compounds was discussed.
Author Magda Caban (FCh / DEA / PAiMŚ)
Magda Caban,,
- Pracownia Analityki i Monitoringu Środowiska
, Piotr Stepnowski (FCh / DEA / LChER)
Piotr Stepnowski,,
- Laboratory of Chemical Environmental Risks
Other language title versions
Journal seriesAnalytica Chimica Acta, ISSN 0003-2670, (A 45 pkt)
Issue year2017
Publication size in sheets0.5
Keywords in Englishionic liquid, chaotropic ions, mobile phase additives, tri-cyclic antidepressants, overloading study, mechanism of retention
ASJC Classification1607 Spectroscopy; 2304 Environmental Chemistry; 1303 Biochemistry; 1602 Analytical Chemistry
Languageen angielski
Score (nominal)45
Score sourcejournalList
ScoreMinisterial score = 45.0, 03-04-2020, ArticleFromJournal
Publication indicators Scopus Citations = 5; WoS Citations = 3; Scopus SNIP (Source Normalised Impact per Paper): 2017 = 1.302; WoS Impact Factor: 2017 = 5.123 (2) - 2017=4.837 (5)
Citation count*6 (2020-04-03)
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