Determination of Paracetamol and Ibuprofen in reversed-phase liquid chromatography mixed-mode with π-interactions using stationary phase with N-alkyl substituted 2,4-dinitroaniline selector

For the first time, the possibility of running in a bimodal HPLC based on combination of the dispersion interactions and hydrophobic effect (reversed phase mode) and stacked parallel-displaced π-interactions (quasi-normal phase mode) for the developed stationary phase AWE-241 with an N-alkyl-substituted 2,4-dinitroaniline selector is demonstrated. Hydrophobic nature of the aromatic selector substituted with two nitro-groups allows it to run in reversed-phase mode, and its electron-deficient character provides additional retention due to stacking parallel-displaced π-interactions, as well as dipole-dipole interactions and interactions via hydrogen bonds. This combination of types of chemical interactions makes it possible to selectively determine substances containing an aromatic group, including polar ones, when operating in the reverse-phase HPLC mode, as well as simultaneously determine polar and hydrophobic compounds with an aromatic group without the need for gradient elution. This advantage of AWE-241 is demonstrated in comparison with commercially available analogues for reverse-phase liquid chromatography (octylsilyl and octadecylsilyl phases), as well as the most common phases containing aromatic groups (phenylhexyl, pentafluorophenyl and pyrenethyl), using the example of simultaneous determination of Paracetamol and Ibuprofen, the active ingredients of the two-component drug «Ibuklin». The metrological characteristics of the developed method for the determination of Paracetamol and Ibuprofen using the AWE-241 stationary phase were evaluated: the range of detectable concentrations was from 0.02 to 0.5 mg/mL, the detection limits were 0.3 and 0.7 μg/mL for Paracetamol and Ibuprofen, respectively. The trueness of the determination was confirmed by the spike solutions method