Construction Of Rapid Detection Methods For Drug Residues Based On Functionalized Nanofiber Membranes

Food safety and environment safety are related to not only the individual health,but also the national economy development and social stability.However,the food safety and environment safety situation are unsatisfactory in our country.In recent years,food safety incidents have occurred frequently,and environmental pollution in some areas has become increasingly serious.Therefore,food safety and environment safety have become hot issues of public concern.Faced with the large variety and quantity of samples and targets,it is of great significance to develop rapid detection methods for drug residues in various food and environment samples.Focusing on this problem,this paper explored a rapid detection system based on one basis,three techniques and four methods.The basis is the functionalized nanofiber mat(NFM).Three types adopted techniques refer to high-throughput sample pretreatment technique,atmospheric pressure ionization technique,and photochemical sensing technique.Accordingly,four methods are established including high-throughput sample pretreatment method,rapid screening method,fluorescence sensing detection method,and naked-eye colorimetric detection method.Specifically,according to the properties of targets and their testing requirements,a series of new functionalized NFM were designed and prepared.The functionalized NFM were further used as the 96-well plate solid-phase extraction(SPE)adsorbent to achieve high-throughput sample pretreatment,as the sampling module of direct analysis real time mass spectrometry(DART-MS)to achieve rapid screening;as the solid-phase carrier of fluorophore pyrene to achieve fluorescence sensing detection,as the solid-phase carrier of copper(?)to achieve naked-eye colorimetric detection.The rapid detections of ?-agonist residues in pork,illegally adulterated sulfonylureas in antidiabetic health-care tea,nitroaromatic compounds in environmental water,and tetracycline residues in milk are taken as examples to verify the feasibility of the novel method system.The main research contents of this paper are as follows:(1)Sodium 4-styrenesulfonate functionalized polyacrylonitrile NFM(SS-PAN NFM)was prepared through thiol-ene “click” reaction and applied as 96-well plate SPE adsorbent for highthroughput sample pretreatment of seven ?-agonists residues in pork samples.The functional modification endowed SS-PAN NFM with superior adsorption performance for target ?-agonists.The proposed sample preparation process required only 3.0 mg of SS-PAN NFM and less than 0.3 min for per sample.The adsorption kinetics,adsorption isotherms and adsorption thermodynamic experiments indicated that the adsorption process was spontaneous(?G<0),the initial adsorption rate can reach 6.03~9.09 mg/(g·min),and the maximum adsorption capacity was calculated to be 48.3 mg/g at 298 K.Moreover,SS-PAN NFM can be reused for12 times without degradation in adsorption capability.Combined with UPLC-MS/MS,the limits of detection(LOD)can reach 0.006~0.24 ?g/kg,the recoveries ranged from 87.2% to111% and the relative standard deviations(RSD)of intra-day and inter-day precisions were in the scope of 1.75%~11.6% and 5.08%~13.5%,respectively.Compared with the existing methods,the SS-PAN NFM-based 96-well plate SPE can process 96 samples at the same time,which greatly improves the efficiency of sample pretreatment.(2)Ionic liquid functionalized PAN NFM(IL-PAN NFM)-based SPE was combined with DART-MS to rapidly detect illegal added sulfonylureas drugs in antidiabetic health-care tea samples.Due to its excellent adsorption performance,IL-PAN NFM can adsorb trace-level targets from complex sample matrix within tens of seconds.After absorbing targets,IL-PAN NFM can be directly used as the sampling module of DART-MS.The targets concentrated on IL-PAN NFM were rapidly desorbed and ionized by excited carrier gas,and then detected by MS.The results indicated that the sensitivity was in the level of 50.0~250 ng/g,while total analysis time did not exceed 1.0 min per sample.Moreover,the stability expressed as RSD varied from 1.70% to 17.3%.Compared with the existing methods,after extracting and enriching targets through SPE,IL-PAN NFM can be directly used as the sampling module of DART-MS,which realized the seamless connection of sample pretreatment and subsequent instrument analysis.A new rapid screening method was thus established.(3)Pyrene functionalized PAN NFM(Py-PAN NFM)was prepared via a green approach based on deep eutectic solvents.The Py-PAN NFM was further employed as solid-state fluorescent sensors for determining 2,4,6-trinitrotoluene(TNT)and 2,4-dinitrotoluene(DNT)in environment water samples.In order to adapt to the hydrophobicity of Py-PAN NFM surface,the water samples were extracted by dichloromethane,and then the extraction solvents were directly dropped onto the Py-PAN NFM.Because of the conversion of sample polarity,Py-PAN NFM does not need to be immersed in the water samples for a long time.The LOD of TNT and DNT can reach 8.81×10–9 M and 2.74×10–8 M,respectively.The Stern-Volmer plots for fluorescence quenching by TNT and DNT displayed an overall linearity in the entire tested concentration range with quenching constants of 2.57×106 M-1 and 3.15×105 M-1,respectively.In addition,the selectivity study indicated that other nitro compounds have an insignificant effect on the fluorescence sensing detection of TNT and DNT.Due to good chemical stability of NFM,Py-PAN NFM can be reused at least 6 times without degradation in fluorescent sensing performance.The theoretical calculations demonstrated that photoinduced electron transfer was involved in the quenching process and the fluorescence lifetime measurements revealed that a static quenching mechanism was suitable to explain the quenching behavior.Compared with the existing methods,the conversion of sample polarity ensured that the targets can immediately interact with the pyrene fluorophores on surface of Py-PAN NFM,thus accelerating the detection speed.Additionally,because the targets were also enriched through the conversion process,the sensing sensitivity has been significantly improved.(4)A new solid-state colorimetric sensor for tetracycline(TC)was developed by directly immobilizing copper(?)on surface of chitosan/polyethylene oxide NFM(Cu@CS/PEO NFM).Due to the complexation between Cu2+ and amino groups of CS,Cu2+ can be immobilized and densely distributed on surface of CS/PEO NFM.After immersing in different concentration of TC solutions,the Cu@CS/PEO NFM can show a color change easily identified by the naked eye from light blue to light green or yellow within 5.0 min,and smartphones can be used for quantitative analysis of the concentration-dependent color changes.Moreover,because the designed colorimetric sensing process relied on the interaction between Cu2+-CS complex and TC,Cu@CS/PEO NFM possessed a more sensitive response to TC and the colorimetric sensing detection will not be interfered by other drugs.The reversible combination of Cu2+ and chitosan ensured that the colorimetric sensing ability of Cu@CS/PEO NFM can be regenerated even after being reused 4 times.The recoveries range from 91.5% to 109%,which are comparable with the results obtained by chromatography method,demonstrating the accuracy of the established method.The relative standard deviations of the intra-day and inter-day precisions are 6.75% and 10.2%,respectively.In addition,the naked eye detection limit of the Cu@CS/PEO NFM-based colorimetric sensing is 65 ?g/kg,which does not exceed the maximum residue limit in milk samples in China(100 ?g/kg).Compared with the existing methods,Cu@CS/PEO NFM,as a solid-state colorimetric sensor,can achieve rapid qualitative and quantitative detection of targets with the naked eye and a smart phone,which has more advantages in convenience,portability and usability.The obtained research results show that due to the excellent adsorption performance,when acted as 96-well plate SPE adsorbent,the functionalized NFM can efficiently isolate and enrich trace-level targets from complex sample matrices,which is the foundation for the successful realization of high-throughput sample pretreatment.The functionalized NFM,as a kind of monolithic membrane,can be used as the sampling module of DART-MS after adsorbing targets through SPE process.The direct combination of sample pretreatment and subsequent instrument analysis guarantees the establishment of a rapid screening method.Moreover,as a solid-phase support,the large specific surface area and abundant functional groups on surface of functionalized NFM can provide a large number of attachment sites for fluorescent/colorimetric probes.The prepared NFM fluorescent/colorimetric sensors are proved to be used for visual rapid detection.