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ILs have been used in liquid chromatography as both mobile phase modifiers [11-13] and structural components of the stationary phase [10, 13-15]. Also, some work has been done on the study of the interaction of ILs with various stationary phases and their potential retention mechanisms, mainly using reversed-phase high performance liquid chromatography (RP-HPLC) [16, 17]. It has been shown that in RP-HPLC, mobile phases with large aqueous fractions decrease miscibility of certain ILs, especially those with bis(triluoromethylsulfonyl)imide anions [18]. In the other hand, the use of columns with mixed stationary phases or hydrophilic interaction liquid chromatography (HILIC) can provide better retention and selectivity for ILs. Besides, the use of mobile phases containing a large fraction of organic solvent is also helpful because it improves the miscibility of certain ionic liquids and facilitates the use of chromatography in conjunction with such techniques as mass spectrometry [18]. However, most reports dealing with the separation of ionic liquids from other compounds after their use as extraction solvents have focused on non polar or moderately polar analytes, such as aromatic compounds and pesticides [7, 9, 20, 21]; there are few reports for polar or hydrophilic analytes [22, 23]. It is worth noting that the majority of these reports do not address whether ILs affect chromatographic separations or pose other difficulties for proper identification and quantification of analytes; in fact, many these works do not even present any chromatogram. Our research group has observed an important influence on chromatography when ILs are present. This behavior has also been reported by Berton et al. [24] while using ionic liquids as extraction solvents. These researchers observed a significant variation in analyte retention when the sample contained an ionic liquid [24].