ABSTRACT
To improve the sensitivity of molecularly imprinted electrochemical sensors, a Pd nanoparticles-modified molecularly imprinted polymer (MIP) film for the determination of trimethoprim (TMP) was developed by thermal polymerization with N, N′-methylene diacrylamide as a functional monomer, Pd nanoparticle as a dopant and ethylene glycol maleic rosinate acrylate as a crosslinking agent.The morphologies and chemical structures of the Pd nano-materials and the imprinted films were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively.The electrochemical properties of the nano-doped and undoped MIP sensors were investigated by cyclic voltammetry and electrochemical impedance spectroscopy.Results showed that the morphologies and chemical structures and the electrochemical properties of the doped molecularly imprinted sensor were remarkably different from those of the undoped imprinted sensor.Linear responses of the imprinted sensor to TMP were observed for concentrations ranging from 5.0×10-7 mol/L to 4.0×10-3 mol/L (R=0.9995), with a detection limit of 3.2×10-8 mol/L (S/N=3).The Pd nanoparticle doped MIP sensors exhibited high selectivity.The chronoamperometry showed that no interference from potential interfering species such as sulfamethoxazole, sulfadiazine, glucose, and urea were noted.The proposed electrochemical sensor was used to determine TMP in actual samples, with average recoveries of 96.8%-102.0%.
ABSTRACT
Objective To explore the feasibility using aluminum tripolyphosphate as the synthesis of aspirin model instead of sulfuric acid catalyst. Methods The thermodynamic functions of the reaction system of salicylic acid and acetic anhydride were calculated according to the Benson group contribution method and Joback group contribution method.The enthalpy change,entropy and Gibbs free energy along with the change of temperature as well as the influence of the molar rate of reactants on the equilibrium conversation rate were also studied.Results In the temperature range of 298.15 K to 358.15 K,the reaction enthalpy was less than zero,and was exothermic reaction,and increase of temperature was not conducive to the reaction.The improvement of mole ratio of salicylic acid and acetic anhydride was helpful to improve the equilibrium conversation rate.The theoretical conversion rate could reach 99.58% when the mole ratio of salicylic acid and acetic anhydride was 3.Conclusion From the viewpoint of thermodynamics, the reaction is practical and feasible.