The performance of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ionic liquid as mobile phase additive in HPLC‐based lipophilicity assessment |
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Authors: | Costas Giaginis Anna Tsantili‐Kakoulidou |
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Institution: | Department of Pharmaceutical Chemistry, School of Pharmacy, University of Athens, Panepistimiopolis, Zografou, Athens 157 71, Greece |
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Abstract: | Ionic liquids have been widely used as green alternative mobile phase additives to shield the residuals silanols groups and modify the stationary/mobile phase HPLC systems. The present study aimed to evaluate the performance of the ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIM]BF4]) in producing extrapolated logkw indices suitable to substitute for octanol–water logP or logD values. The effect of EMIM]BF4] was investigated for a set of basic and neutral drugs using two different columns, BDS and ABZ+. EMIM]BF4] was added simply alone or in combination with n‐octanol and was compared with the conventional masking agent n‐decylamine. EMIM]BF4] reduced the retention by suppressing silanophilic interactions, althoug to a lower extent than n‐decylamine. Addition of n‐octanol further decreased the retention by shielding silanol sites on BDS and/or interacting with polar groups through hydrogen bonding on ABZ+. Logkw/logD7.4 relationships proved moderate compared with those derived upon addition of n‐decylamine. They were considerably improved upon the introduction of protonated fraction F+ in the correlation, reflecting ion pair formation between the chaotropic anion BF4]‐ and the protonated basic compounds. In this aspect, the ionic liquid EMIM]BF4], although efficient as a masking agent, cannot be recommended as mobile phase additive to reproduce octanol–water partitioning. Copyright © 2010 John Wiley & Sons, Ltd. |
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Keywords: | reversed‐phase liquid chromatography ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate n‐octanol lipophilicity |
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