| LC-MS/MS is a qualitative and quantitative analysis method for sulfonamides in fish products.High resolution mass spectrometry technology has high quality accuracy and resolution.It can be used for quantitative and qualitative analysis of trace components in complex matrix,and its advantages are remarkable.Because sulfonamides bind to fish plasma albumin,the recovery rate is low.This study analyzed the interaction between protein macromolecules and sulfonamides in fish,and explored the ways to dissociate and eliminate the interaction,so as to improve the recovery of sulfonamides in fish samples and achieve the purpose of accurate quantification.A screening method was established for simultaneous determination of 24 antibiotic residues in fish,including quinolones,tetracyclines,chloramphenicols,sulfonamides and macrolides.A screening method was established for simultaneous determination of 24 antibiotic residues in fish,including quinolones,tetracyclines,chloramphenicols,sulfonamides and macrolides.This paper is divided into the following four parts:In the first part,based on the current situation of fish food safety,the interaction between sulfonamides and protein macromolecules in fish and the necessity of eliminating them were reviewed.The general situation of screening and analysis of common antibiotic residues in fish food was discussed from three perspectives:common antibiotic residues,sample pretreatment methods and detection methods of common antibiotic residues.The second part,in order to solve the problem of low recovery rate of sulfonamides in fish,the aim is to dissociate drugs interacting with protein macromolecules in fish.BSA carrier proteins were selected and analyzed by high performance liquid chromatography-Q-TOF-MS with sulfamethoxazole and sulfadoxine as representative drugs.BSA and sulfonamide drug complex ion peak response intensity and sulfonamide drug recovery rate in incubation system were used to investigate the interaction model and characteristics of protein macromolecules and sulfonamides in fish.By optimizing incubation conditions and LC-MS parameters,BSA forms a protein-sulfonamide complex with a stoichiometric ratio of 1:1 when the concentration ratio of BSA to sulfamethoxazole and sulfadoxin is 1:3(v/v).At the same time,the recovery of sulfamethoxazole and sulfadoxine in incubation system decreased to 61.4%and53.7%,respectively.By optimizing the incubation system,a sulfonamide-protein macromolecule interaction model was constructed.The third part,when 0.3%acetic acid was added to the BSA and sulfonamide incubation system,the pH value of the system was adjusted to3.50+0.1,and the complex peaks disappeared in the mass spectrometry.At the same time,the incubation system was centrifuged and the supernatant was taken for detection and analysis.The results showed that no BSA was detected in the supernatant,while the recovery of sulfamethoxazole and sulfadoxine increased to 90.2%and 96.9%.The results showed that the interaction between BSA and sulfonamides was eliminated,and the bound sulfonamides were converted into free state,thus improving the recovery of sulfonamides in fish and achieving the purpose of accurate quantitative analysis.The fourth part,based on the interaction dissociation method of BSA and sulfonamides,a method for the determination of 24 antibiotic residues in fish meat was established by dispersed solid phase extraction and ultra-high performanceliquidchromatography-quadrupoletime-of-flightmass spectrometry.The results showed that in the linear range of 1μg/kg~500μg/kg,the matrix effect of 24 antibiotics was in the range of-11.81~16.34,while the matrix effect was weak.The correlation coefficients R~2 of 24 compounds were all greater than 0.97,the detection limit and quantitative limit were 0.31μg/kg~16.37μg/kg and 1.03μg/kg~54.57μg/kg.After the establishment of the method,37 fish samples were tested and 3 positive samples were detected,including tetracycline,chlortetracycline and florfenicol.The detection rate was8.11%. |
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