Study On The Novel Detection Methods Of Veterinary Drug Residues Based On Sample Pretreatment Technologies Of Polyaniline Nanofibers Mat

Nowadays,food safety and environmental pollution have become an urgent problem concerning the national economy and people’s livelihood.The rapid development of national economy and the continuous improvement of people’s living standards have greatly increased the demand for animal-derived food such as meat,eggs and milk.The safety of animal-derived food is the top priority of food safety.However,the improper use of veterinary drugs,such as the abuse of antibiotics and illegal addition of banned drugs,will cause the veterinary drug residues in food of animal origin.The large-scale use and continuous discharge of veterinary drugs enable them to enter environment through runoff,infiltration or other forms.Therefore,the monitoring of veterinary drug residues in food and environmental samples is of important social significance.The matrix of food and environmental samples is complex,and the content of target substances is very low.Thus,the samples must be pretreated before testing.Solidphase extraction(SPE)technology is one of the mainstream sample pretreatment methods and nanofibers based SPE has become the forefront and hotspot of analytical chemistry.In this paper,combined with nanofibers based SPE and ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)detection technology,analytical methods were established to provide approaches and new ideas for the separation and detection of veterinary drug residues in environmental samples and animal-derived foods.The main research contents of this paper are as follows:(1)Non-steroidal anti-inflammatory drugs(NSAIDs)are one kinds of the most widely used pharmaceuticals in the world.NSAIDs are of high polarity and good hydrophilicity.Considering the low extraction efficiency of adsorbents,the complex treatment process,large time and organic solvents consumption of the current SPE methods for NSAIDs,polyaniline nanofibers mat(PANI NFsM)with suitable molecular structure and morphology were developed.The surface functional groups and morphologies of the nanofibers were characterized by infrared spectroscopy,scanning electron microscope and other methods.The adsorption and desorption properties of PANI NFsM on NSAIDs were investigated by adsorption isotherm,adsorption thermodynamics and adsorption/desorption kinetics.Finally,PANI NFsM was used as SPE adsorbent to enrich and purify NSAIDs in environmental water samples.The results show that PANI NFsM has high adsorption capability and high mass transfer efficiency for NSAIDs.The maximum static adsorption capacity was 33.1 mg/g,36.9 mg/g and 49.8 mg/g at 298 K,318K and 338 K,respectively,and both the adsorption and desorption equilibriums could be completed within 5.0 min.Compared with other methods,lower detection limit(0.2-5.0 ng/L)and better recoveries(85.0%-99.7%,1.4%<RSD<11.1%,n=6)were obtained with only 3.0 mg of PANI NFsM and 0.7mL of organic solvent.It is time-saving,24 samples can be handled simultaneously and the average preparation time per sample is less than one minute.PANI NFsM can be used at least 20 times without any reduction in extraction efficiency.Finally,the proposed method was applied to the analysis of hospital wastewater,water source water(lake water,river water)and factory water,proving the practical application feasibility of the method.(2)Fluoroquinolone(FQs)drugs are synthetic antibacterials widely used in the treatment of various bacterial infections.The monitoring of FQs residues in environmental water is of great significance in food safety and environmental protection.The sulfonated polyaniline nanofiber mat(SPANI NFsM)was prepared by one-step synthesis.By density functional calculation and comparison of adsorption capacity of PANI NFsM and SPANI NFsM for FQs,the interaction mechanisms between the adsorbent and adsorbates were investigated.The adsorption/desorption properties of SPANI NFsM for FQs were investigated by adsorption isotherm,adsorption thermodynamics and adsorption/desorption kinetics.The results show that SPANI NFsM has high adsorption capability and high mass transfer efficiency for FQs.The maximum static adsorption capacity was 6.02 mg/g,7.21 mg/g and 8.01 mg/g at 298 K,318 K and 338 K,respectively,and both the adsorption and desorption equilibriums could be completed within 5.0 min.Combined with SPANI NFsM based SPE and UPLC-MS/MS,the detection method for FQs in environmental water samples was established and applied in actual water samples.Compared with the methods reported in the literatures,the new method has the advantages of shorter time(2.0 min),less consumption of adsorbent(4.0 mg),lower detection limit(0.5-1.5 g/L),excellent reusable performance(>20 times),and good recoveries(83.7%-109.0%)and precision(<12.1%).(3)In the practical food safety monitoring,the number of samples to detect tends to be huge.96-well plate micro-solid phase extraction(μ-SPE)technology based on SPANI NFsM was established for high-throughput detection of FQs in animal-derived foods.By comparing with the literature methods and the national standard method(No.1025 of the ministry of agriculture),the new method was evaluated thoroughly and comprehensively.The results show that the new method is suitable for more kinds of samples(animal muscle,pig liver,pig kidney,egg and milk)and the required sample amount(0.50 g),adsorbent dosage(5.0 mg)and organic solvent(0.7 mL)were relatively small.96 samples can be handled simultaneously and the average sample preparation time per sample is less than 0.2 min.The extraction solvents of most of the existing methods were organic solvents,while EDTA-McIlvaine’s buffer used in the new method is green,efficient and can be subjected to μ-SPE directly.Finally,the new method was applied to the analysis of real samples,providing reference data for the FQs residues in animal derived foods.(4)In view of the multiple pretreatment steps and large organic solvent consumption of the present sample preparation methods for paracetamol(PCM)and chloramphenicol(CAP)in animal derived food samples.EDTA-McIlvaine’s buffer was firstly used as extraction solvents for PCM and CAP,and PANI NFsM was choosen as SPE adsorbent for purification and enrichment of the targets.Combined with UPLC-MS/MS,the simultaneous detection method of the two classes of drugs in meat was eatablished.The methodological effectiveness of the method was evaluated.Compared with the national standard methods(GB 29683-2013、No.781 of the ministry of agriculture)and the reported methods,the new method was simplified greatly with much fewer sample preparation procedures(four steps).Besides,the new method needs only 40% weight of the sample in the national standard methods.In addition,a much lower consumption of sorbent(6.0 mg),handling time(less than 2.0 min)and organic solvent(0.7 mL)were achieved,reducing the cost and improving the work efficiency.Finally,the new method was applied to the analysis of real samples to verify the feasibility and practical application of the method.The results of this paper show that PANI NFsM has the advantages of fast mass transfer efficiency,large adsorption capacity and reusability.Based on the SPE of PANI NFsM,only a few milligrams of adsorbent and hundreds of microliters of eluent were needed while achieving efficient extraction of target analytes in various practical samples.The methods presented good analytical performance including detection limit,linearity,precision,recovery,etc.At the same time,it overcomes the shortcomings of the conventional SPE,such as low extraction efficiency of adsorbents,large consumption of organic solvent and long-time treatment.With the advantages of high sensitivity,simple and fast operation,the method is in conformity with the trend of the “Green Chemistry”.