Preparation and Evaluation of 3,5-Dinitrobenzoyl-Bonded Silica Gel Stationary Phase for HPLC

Column packing materials are always a key factor influencing the development of high-performance liquid chromatography (HPLC). In this paper, a new preparation method of 3,5-dinitrobenzoyl-bonded silica gel stationary phase (DNB) for HPLC was developed by using N-(β-aminoethyl)-γ-aminopropyl-methyldimethoxy silane as coupling reagent. Its structure was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy, and thermal analysis. The surface concentration of 3,5-dinitrobenzoyl ligand is 2.082 μmol m−2, according to the carbon content of elemental analysis. The chromatographic performance of new packing was evaluated by using different solute probes, such as alkylbenzenes, polycyclic hydrocarbons (PAHs), phenols, naphthalene derivatives, nitrophenol positional isomers, and sulfonamides. The results show that DNB was of the reversed-phase packing kind with weak hydrophobicity and versatile chromatographic property compared with octadecyl silane. The charge transfer between the dinitrobenzoyl ligand and the analytes plays a significant role in the separation of phenols and naphthalene derivatives. In addition, electrostatic, hydrogen-bonding, and dipole-dipole interactions are responsible for the above separations, which improve the selectivity of DNB for solutes. An advantage of DNB is that it is suitable for the separation of the basic compounds containing nitrogen atoms without a capped process because the spacer containing nitrogen atoms can shield the residual silanols from DNB.