Preparation And Adsorption Properties Of Molecularly Imprinted Polymers Based On The Determination Of Norfloxacin Residues In Food

Norfloxacin(NOR)is a fluoroquinolones(FQs)antibiotic.It could be widely used in prevention and treatment of infectious diseases in animal,owing to its better antibacterial effect,long half life,and lower price.However,the abusing of NOR antibiotics in livestock and poultry breeding would cause the residue of NOR in animal derived food.It could indirectly threaten human health,and even causes drug resistance.At present,the detection of NOR antibiotics has been gradually simplified.Thus,the pretreatment of sample is becoming the key to the determination of NOR residues in complex matrix of animal derived foods.Molecular imprinting technology(MIT)refers to the process of preparing molecularly imprinted polymers(MIPs)with specific recognition for template molecules.This techniques has become one of the hot research topics at home and abroad since it can provide molecular combinations with desired structure and unique physical and chemical properties,and has been widely used in food safety inspection and other fields.In recent years,several researchers have begun to establish molecular models to simulate the design of MIPs.Here,using the quantum chemistry LC-WPBE/6-31G(d,p)method,the self-assembly system of NOR with different functional monomers was simulated,and the best functional monomer with stable complex configuration was selected.In this work,NOR was chosen as the template molecule;methacrylic acid(MAA),4-vinyl pyridine(4-VPy),and2-vinyl-4,6-diamino-1,3,5-triazine(VDAT)were selected as the functional monomers;trihydroxymethylpropyl trimethylacrylate(TRIM),ethylene glycol dimethacrylate(EDMA),and pentaerythritol triacrylate(PETA)were used as the cross-linking agents;methanol(MT),acetonitrile(ACN),chloroform(CAS),water(H₂O),and toluene(TL)were taken as the solvents.The cross-linking agents and solvent were optimized by binding energy and solvation energy,respectively.The nature of imprinting interaction between NOR and MAA was revealed based on the atom in molecule theory(AIM).Meanwhile,the selectivity of stable NOR-MAA complex was simulated.The calculated results revealed that,when the interaction ratio between NOR and MAA was 1:6,TRIM was as cross-linking agents,and ACN was as solvent,the hydrogen bond interaction between NOR and MAA was strongest and the configuration energy was the lowest.The stable NOR-MAA complex showed good selectivity for NOR,and the order of its selective adsorption capacities for its structural analogues and phenol were ciprofloxacin(CIP),ofloxacin(OFL),phenol.On the basis of the guidance of theoretical calculation,NOR-MIPs were synthesized using the precipitation polymerization,when the MAA was as the functional monomer,TRIM was used as the cross-linking agent,and ACN was as the solvent.Then,their properties and morphology had been characterized.The experiment results indicated that,when the imprinting ratio between NOR and MAA was 1:6,the prepared NOR-MIPs samples were spherical,with an average particle diameter of 105 nm.The dissociation equilibrium constant(K_d)and the maximum apparent adsorption capacity(Q_max)were K_d1=90.91 mg/L and Q_max1=92.25 mg/g,and K_d2=266.67 mg/L and Q_max2=197.48 mg/g,respectively.The adsorption of NOR-MIPs to NOR was exothermic process.The adsorption capacity was largest at p H=6,and the coexisting ions in the solution had different degrees of inhibition on the adsorption of MIPs.The study of selectivity property indicated that MIPs have relatively satisfactory adsorption ability for the analogues of NOR.On the other hand,the adsorption ability of MIPs is poor,when the structure of sample is large different from NOR.Finally,the NOR-MIPs were used as specific adsorption materials to enrich and separate the NOR from the spiked chicken samples.The results of four cycles showed that the saturated adsorption capacity of NOR-MIPs was 21.89 mg/g,and the adsorption rate was 82.67?96.52%.