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The performance of 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ionic liquid as mobile phase additive in HPLC‐based lipophilicity assessment
Author(s) -
Giaginis Costas,
TsantiliKakoulidou Anna
Publication year - 2011
Publication title -
biomedical chromatography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 65
eISSN - 1099-0801
pISSN - 0269-3879
DOI - 10.1002/bmc.1491
Subject(s) - chemistry , ionic liquid , lipophilicity , tetrafluoroborate , phase (matter) , high performance liquid chromatography , octanol , protonation , ion , chromatography , partition coefficient , organic chemistry , catalysis
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 log k w indices suitable to substitute for octanol–water log P or log D 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 + . Log k w /log D 7.4 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.