Effect of concentration of ionic liquid 1-butyl-3-methylimidazolium, tetrafuoroborate, for retention and separation of some amino and nucleic acids

In this paper, three nucleic acids such as cytosine, cytidine, and thymine and two amino acids, such as D-tryptophan and N-carbobenzyloxy-D-phenylalanine, were chromatographed using ionic liquid as an additive for the mobile phase in high performance liquid chromatography (HPLC). Ionic liquid, 1-butyl-3-methylimidazolium tetrafuloroborate ([BMIm](+) [BF4](-) ), was used. The nucleic acid eluent was 5 vol. % of the modifier (methanol:acetonitrile = 95:5 (vol. %)), in 10 mM of sodium phosphate monobasic, with addition of 0.5, 2.0, and 4.0 mmol/L of ionic liquid. Separation of nucleic acids was obtained on a commercially available octadecyl silica column (4.6 x 150 mm i.d., and particle size 5 mu m). In the case of D-amino acids, the mobile phase was 65% methanol in water, with additions of 0.5, 1.0, 2.0, 8.0, 12.0, and 15.0 mmol/L of ionic liquid. The experiments were performed on a stainless steel column, 3.9 x 300 mm i.d., and particle size 15 mu m, packed with octadecyl-bonded silica at the laboratory. Effects of the concentration of ionic liquid for retention and separation of some nucleic and amino acids were discussed. The results showed the potential application of ionic liquid as a mobile phase additive in liquid chromatography.