Preparation of Carboxybetaine-based Hydrophilic Interaction Chromatographic Column and Its Performance Exploration / 分析化学

2-(Dimethylamino)ethyl methacrylate and sodium monochloroacetate were employed to synthesize [2-(Methacryloyloxy)ethyl] dimethyl ammonium acetate (CBMA) functional monomer.CBMA was grafted on the surface of silica by surface initiated atom transfer radical polymerization (SI-ATRP) to obtain silica-CBMA hydrophilic interaction stationary phase.Three silica-CBMA stationary phases with different grafted density of CBMA monomer were synthesized in SI-ATRP progress by changing the concentration of CBMA under the same conditions.The ability to separate organic acid compounds of the synthesized silica-CBMA stationary phases was evaluated under different conditions, including effects of pH value, salt concentration and content of water of mobile phase on retention of solutes.The results showed that the stationary phases could effectively separate organic acid compounds in HILIC mode, which followed a mixed mode of chromatography of ion exchange and hydrophilic interaction.The retention of solutes decreased with the increases of salt concentration of mobile phase, which consistent with the characteristics of ion exchange;the pH value of mobile phase had significant influence on ionization of the stationary phase and solutes, i.e., the retention of solutes increased as the increasing of pH value of mobile phase.However, the retention of solutes decreased with the increasing of the content of water in mobile phase, which was the typical characteristic of HILIC.The method of hydrophilic interaction chromatography combined with silica-CBMA stationary phases could conveniently determinate the content of vitamin C and rutin in rutin tablets, providing a new method for the separation and determination of strong polar samples.

Preparation of Polyacrylamide Resin and Its Adsorption Properties on 2,4-Dichlorophenoxyacetic Acid / 分析化学

Polyacrylamide resin was synthesized via surface-initiated atom transfer radical polymerization ( SI-ATRP) method. Acrylic amide ( AM) was grafted onto the surface of the chloromethyl polystyrene resin via SI-ATRP in the CuBr/2, 2'-bipyridine ( Bpy) system as catalyst at room temperature. The compositions of polyacrylamide resin were determined by means of elementary analysis, FT-IR analysis and scanning electron microscopy ( SEM) . The adsorption properties, the parameters of kinetics and the thermodynamics of the resin were evaluated in details, respectively. As the results, adsorption capacity of 2,4-dichlorophenoxyacetic acid (2,4-D) increased with the initial concentrations of solution increasing at room temperature, and its highest adsorption capacity was 111. 0 mg/g with solution concentration of 8 mmol/L. Adsorption isotherm at room temperature was determined and modeled with Langmuir and Freundlich equations. The thermodynamic equilibrium functions were calculated to be ΔG0, hence, the adsorption was spontaneous, endothermic and entropy increasing. The kinetics fitted the pseudo-second-order well. The polyacrylamide-chloromethyl polystyrene (PAM-CMCPS) resin was used for the adsorption of 2,4-D in orange sample, and good results were obtained.