The Effect of 1-Methyl-3-butylimadazolium Tetrafluoroborate Ionic Liquid as a Mobile Phase Additive on the Retention Behavior of Nitroaromatic Explosives and Related Compounds

In this study, the use of the ionic liquid 1-butyl-3-methylimidazolium terafluoroborate (BMIM[BF4]) as an additive in the separation of mixtures containing nitroaromatic explosives and related compounds in reversed-phase high performance liquid chromatography is reported. The analytes used are: 1,3-DNB, 1,3,5-TNB, 2-A-4,6-DNT, 2,4-DNT, HMX, NB, RDX, TNT, 2NT, 3NT, 4 NT, tetryl, 2,6-DNT and 4A-2,6-DNT. The effects of the concentration of the ionic liquid on the retention, capacity factors and resolution of these analytes were studied. Mobile phases containing of 10% methanol with 0, 5, 10 and 20 mM BMIM[BF4], 20% methanol with 0, 5 and 20 mM BMIM[BF4] and 100% of 20 mM BMIM[BF4] were used for this study. All the mobile phases containing ionic liquids gave smaller capacity factors for the analytes and a run time that is smaller by 10-20 minutes compared to mobile phases containing methanol as a modifier. The number of compounds that have full or partial resolution is affected also by the concentration of the ionic liquid in the mobile phase. The elution order of the analytes was not affected by the addition of ionic liquids. These results show the potential application of ionic liquid BMIM[BF4] as a mobile phase additive to improve the resolution, decrease the analysis time and to reduce the organic solvent consumption in the HPLC analysis of the nitroaromatic explosives and related compounds.