| Nowadays,people need more animal origin foodstuffs every day,so the residue of veterinary drugs in our foods become one of the most noticeable problems for security,which causes acute or chronic disease to public health,and bacteria tolerance to the drug,also causes many potential harm indirectly to health by circumstance and food chain.More and more researchers are studying on the determination of veterinary drug residues.We also need to develop some simple,sensitive and exact methods.Solid-phase microextraction?SPME?has been widely used for the extraction of various samples due to the advantages of using the minimum or completely elimination the use of organic solvent,and integrating sampling,extraction,concentration,and sample introduction into a single step in 1990 s.However,most of the commercial coatings have no selectivity towards targets.In this paper,through modifying the molecularly imprinted materials and aptamer on the solid-phase microextraction fiber to improve the selectivity and sensitivity of detection method.1.In this section,a quick and specific pretreatment method based on a series of extraction clean-up disks,consisting of molecularly imprinted polymer monoliths and C18 adsorbent,was developed for the specific enrichment of salbutamol and clenbuterol residues in food.The molecularly imprinted monolithic polymer disk was synthesized using salbutamol as a template through a one-step synthesis process.It can simultaneously and specifically recognize salbutamol and clenbuterol.The monolithic polymer disk and series of C18 disks were assembled with a syringe to form a set of tailor-made devices for the extraction of target molecules.In a single run,salbutamol and clenbuterol can be specifically extracted,cleaned,and eluted by methanol / acetic acid / H2 O.The target molecules,after a silylation derivatization reaction were detected by gas chromatography-mass spectrometry.The parameters including solvent desorption,sample pH,and the cycles of reloading were investigated and discussed.Under the optimized extraction and clean-up conditions,the limits of detection and quantitation were determined as 0.018-0.022 and 0.042-0.049 ng?g-1 for salbutamol and clenbuterol,respectively.The assay described was convenient,rapid,and specific;thereby potentiated as efficient in the high-throughput analysis of ?2-agonists residues in real food samples.2.This study aimed to simultaneously determine three ?2-agonists?clenbuterol,salbutamol,and ractopamine?in pork samples using novel stir bar array sorptive extraction coupled with gas chromatography–mass spectrometry.Pencil refill was employed as the substrate of stir,which was covered with carboxyl graphene sheets and polyluminol coating.The coating was simply prepared by electrochemical deposition of luminol at a voltage of 0–0.6 V.Then,an automatic device with the stir bar array for extraction was used.The conditions for the extraction were optimized.Under the optimum extraction conditions,with toluene as the extraction solvent,the extraction and desorption times were 20 min.A good linearity of three ?2-agonists was obtained in the range of 0.5–100 ng/g by gas chromatography–mass spectrometry detection.The recovery of clenbuterol,salbutamol,and ractopamine in spiked pork samples ranged from 88.7% to 93.2%,85.5% to 94.2%,and 85.7% to 93.9%,respectively,with the relative standard deviations less than 10%.The detection limits were in the range of 0.022–0.091 ng/g for pork samples.The extraction coating with high extraction capacity was simply fabricated by the electrochemical method,which could simplify the pretreatment procedures.Moreover,the array could extract several samples simultaneously and improve the pretreatment efficiency.3.In this paper,a novel three dimensional?3D?M×N type aptamer-functionalized stir bars array was developed for selective enrichment of multiplex antibiotic residues,with three chloramphenicols?CAPs?as models,from several food samples.Firstly,gold nanoparticles were electrodeposited on gold wire??=0.2 mm?which was wound around a conductive indium tin oxide glassy stir bar.Then,the stir bar was immersed into thiol-functionalized aptamers solution which can specifically recognize three CAPs.The aptamer can be covalently immobilized on AuNPs through Au-S bonds.Thus a 3D aptamer-functionalized stir bar interface was built up,it was employed for specifically sorptive extraction CAPs from the food samples with matrix complex based on the high affinity of aptamer for the targets.Finally,several similar stir bars were assembled together into an array for simultaneous enrichment of three CAPs from 12 samples in one run.Afterwards,the adsorbed targets were washed away by p H 8.5 0.1M Tris-HCl buffer,then detected by high performance liquid chromatography?HPLC?-Diode Array Detector?DAD?.Under the optimized conditions,the limits of detection?LOD?and quantitation?LOQ?were determined as 0.462-1.46 and 1.52-4.22 ng g-1 for several CAPs,respectively.The stir bars array can be applied in replicate batch-extraction at least for 60 extraction cycles with recovery over 80%.The SBASE assay coupled with HPLC detection possessed advantages of high-throughput,high selectivity and adsorption capacity in one run.Furthermore,it is environmentally friendly without using organic solution during the whole extraction process.Thus,the method is a universal platform which can be extended to selective extraction of other organic pollutants residues if changing the modified aptamers. |
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