Construction And Application In Milk Of Ciprofloxacin Hydrochloride Molecularly Imprinted Electrochemical Sensor

As a food with increasing demand,the safety of milk has been the focus of public concern.In the process of feeding dairy cows,some breeding units will feed ciprofloxacin hydrochloride（CPFX）and other antibiotics to reduce the probability of death of dairy cows due to infection and pathogen,so as to improve milk yield.However,the intake of milk containing antibiotics will cause certain harm to human health,so it is very important to monitor CPFX.Studies have confirmed that CPFX is difficult to degrade and easy to remain in dairy cows.The Ministry of Agriculture of China has clearly stipulated that the residual amount of CPFX in animal food should not exceed 100μg kg^-1～300μg kg^-1.Therefore,it is extremely important to develop a sensitive and efficient method for the detection of residual CPFX in milk.In this study,two kinds of sensors were prepared by using molecularly imprinted electrochemical technology to detect CPFX in milk.The specific contents are as follows:（1）The glassy carbon electrode（GCE）surface was polymerized with AuNPs by electrochemical cyclic voltammetry（CV）,and then Cs-CoFe-Mo Fs was dripped onto the AuNPs/GCE surface.The CoFe-Mo Fs was fixed on the AuNPs/GCE surface by the film-forming property of chitosan（Cs）,and CS-CoFe-Mo Fs/AuNPs/GCE was obtained.Then CV was used for electrochemical polymerization of molecular imprinted polymers（MIPs）with Py as functional monomer and CPFX as template molecule on the surface of modified electrode.The MIPs/Cs-CoFe-MOFs/AuNPs/GCE sensors were obtained by elution of template molecules.Due to the high specific surface area and porosity of Cs-CoFe-MOFs,the area of the polymerized imprinted film can be extended,so more imprinted sites can be obtained after elution by the sensor.Compared with MIPs/AuNPs/GCE,the detection limit of MIPs/GCE can be reduced several times.This sensor constructing process of SEM,electrochemical differential pulse voltammetry（DPV）and impedance spectroscopy（EIS）analysis showed that after the success of the sensor to build,through optimizing the experiment got the optimum parameters of sensors to build,at the same time,the sensor also has good selectivity,stability and repeatability,the detection limit of 3.3 pg m L^-1,The linear range was 0.05～500 ng m L^-1,and the recoveries were in the range of 2.89%～5.50%,which was feasible compared with the HPLC method.（2）After AuNPs was deposited on the surface of GCE by potentiostatic method,ZIF-67-Nafion/AuNPs/GCE modified electrode was obtained by dropping ZIF-67-Nafion/AuNPs/GCE modified electrode.The good film formation of perfluorinated sulfonic acid（Nafion）firmly fixed ZIF-67 on the electrode surface.Then,the modified electrode was potentiostatic polymerization using m-phenylenediamine（m PD）as the functional monomer and CPFX as the template molecule of MIPs to obtain the MIPs/ZIF-67-Nafion/AuNPs/GCE sensor.Because the m-phenylenediamine has two aromatic amino groups with relatively independent spatial structure,the MIPs obtained by its polymerization has a stronger spatial structure than Py and CPFX,resulting in a longer elutions time of template molecules.MIPs/ZIF-67-Nafion/AuNPs/GCE obtained by this method also had a low detection limit of 0.023 ng m L^-1and a linear range of 0.005～5μg m L^-1.After successfully characterizing the construction process of the sensor by applying CV,EIS and SEM,the optimal experimental parameters are obtained by optimizing the sensor.Performance tests showed that MIPs/ZIF-67-Nafion/AuNPs/GCE sensor had good selectivity,stability and reproducibility,and the spiked recoveries in milk ranged from 95.86 to 104.06%with RSD ranging from 1.89 to 4.82%,which was also feasible compared with HPLC method.