Preparation of PDMAEMA Hydrophilic Interaction Chromatographic Stationary Phase by Atom Transfer Radical Polymerization and Its Chromatographic Properties

Surface-initiated atom transfer radical polymerization (SI-ATRP) technique is an attractive polymer grafting, in which the polymer chains with controlled molecular weight and molecular weight distribution can be obtained. The graft density is controlled by the surfaces density of the initiator, and the graft chain length by the ratio of monomer to initiator or the polymerization time. It plays an important role in the preparation of functional materials in the field of separation science. In this paper, SI-AIRY of dimethylaminoethyl methacrylate (DMAEMA) was conducted on the surface of 5 mu m silica using 2-bromoisobutyryl bromide as the initiator and CuBr/1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA) as the catalytic system, a novel P-DMAEMA chromatographic stationary phase was obtained in DMF medium at 60 degrees C. The three stationary phases with different chain lengths of the grafted DMAEMA were tried by manipulating the polymeric conditions. The Concentrations of DMAEMA were changed but the polymerization time kept the same for three DMAEMA-grafted silica. For the first one named as ATRP1, [DMAEMA]/ [initiator]/[CuBr]/[PMDETA] ratios were selected as 50 : 2 : 1 : 2, the second (ATRP2), [DMAEMA]/[initiator]/[CuBr]/ [PMDETA] ratios as 75 : 2 : 1 : 2, and the third (ATRP3), [DMAEMA]/[initiator]/[CuBr]/[PMDETA] ratios as 100 : 2 : 1 : 2. Three stationary phases were characterized by means of elementary analysis. The synthesized stationary phases were evaluated in detail to determine its separability, effect of the content of water and the salt concentration in the mobile phase on the retention of solutes. The stationary phases can effectively separate seven nucleosides in HILIC mode, and the retention time of nucleosides have a positive relationship with increasing the chain lengths of the grafted poly(DMAEMA). It was used for separation and determination of some nucleoside compounds in Ningxinbao Capsule. Compared with NH2 hydrophilic interaction chromatographic column for separation of these compounds under the same chromatographic conditions, the separation efficiency is better. The results showed that the retention of solutes was controlled by partitioning between mobile phase and a water-rich layer immobilized on the stationary phase. The stationary phase has good chromatographic properties for separation of polar compounds.