Sensitive Determination Of Several Anticoccidial Drugs By Surface-enhanced Raman Spectroscopy

Coccidiosis is a common and serious parasitic disease in aquaculture.This parasitic disease brings huge economic losses to the aquaculture industry every year,so breeders regularly add a large number of anti-coccidiosis drugs to animal feed to prevent coccidiosis.However,non-standard drug addition methods will cause coccidia drug residues in animals to cause harm to the health of eaters.The traditional detection methods of anti-coccidial drugs are time-consuming and laborious,so we need a new detection method to detect anti-coccidial drug residues in meat products.Surface-enhanced Raman spectroscopy（SERS）is an analytical method with the advantages of high sensitivity,rich spectral information,easy operation and fast detection speed.Based on the SERS principle,we have successfully studied several SERS sensors for the determination of anti-coccidial drugs in meat samples.The specific research contents are as follows:Two surface-enhanced Raman spectroscopy methods based on silver nanoparticles were established for the sensitive detection of dinitolmide and toltrazuril.The nanoparticles were characterized by ultraviolet spectroscopy and scanning electron microscope,and it was inferred that the enhancement mechanism of two new surface enhanced Raman systems was chemical enhancement.The content of nanoparticles,p H,ionic strength and mixing time of nanoparticles and drugs in the system were optimized.Under the best experimental conditions,there was a good linear relationship between the drug concentration and the Raman signal when the concentration range of dinitolmide was 3.33～33.30 nmol L^-1(I_SERS=1470.06 c+28676.39,c:nmol L^-1,R²=0.998)and the concentration range of toltrazuril was 3.33～66.70 nmol L^-1(I_SERS=1327.46 c+46556.59,c:nmol L^-1,R²=0.999).In these two systems,the detection limit of dinitolmide（LOD）（S/N=3）was 0.95 nmol L^-1,and the detection limit of toltrazuril was 1.04 nmol L^-1.It was calculated that the enhancement factors（EF）of the two systems in the detection of dinitolmide and toltrazuril are 1.76×10^-5 and 1.27×10^-5 respectively.The effects of different interfering substances(K⁺,Mg²⁺,Zn²⁺,Ca²⁺,Cu²⁺,glucose and monensin)on the determination of dinitrotropide and totrazuril were studied.No drug residues were found in the determination of dinitrotropide and toltrazuril in duck and chicken samples by two SERS methods.In the recovery experiment,the recovery of dinitolmide was 98.09%～105.39%and the relative standard deviation（RSD）was between 1.78%～4.47%（n=5）.The recovery rate of toltrazuril was 96.94%～98.35%and the RSD was between 1.45%～5.99%（n=5）.A new type of Au/γ-Al₂O₃ nanoparticles was synthesized and used as a substrate for the determination of trimethoprim in samples by surface-enhanced Raman spectroscopy.The newly prepared Au/γ-Al₂O₃ nanoparticles were characterized by ultraviolet spectroscopy,infrared spectroscopy and scanning electron microscopy.The experimental conditions such as the number of Au/γ-Al₂O₃ nanoparticles,p H,ionic strength and mixing time of nanoparticles and drugs in the system were optimized.Under the optimal conditions,the concentration range of trimethoprim has a good linear relationship(I_SERS=107.99c+44870.51,c:nmol L^-1,R²=0.992)in the range of 3.33～300.00 nmol L^-1.The detection LOD（S/N=3）was 2.35 nmol L^-1.The EF of the system in the detection of trimethoprim was 4.23×10⁶.The effects of several common interfering substances on the determination of trimethoprim were studied(K⁺,Mg²⁺,Zn²⁺,Ca²⁺,Cu²⁺,glucose and monensin).No trimethoprim was detected in chicken and duck samples.In the recovery experiment,the recovery of trimethoprim samples was between 97.90%and 102.91%.The RSD was 1.38%～4.41%（n=5）.A new type ofβ-cyclodextrin/Au NPs/γ-Al₂O₃ nanoparticles was synthesized and used as the substrate of surface-enhanced Raman spectroscopy for the determination of nitrofurazone.Theβ-cyclodextrin/Au NPs/γ-Al₂O₃ nanoparticles were characterized by ultraviolet spectroscopy,infrared spectroscopy and scanning electron microscopy.The amount ofβ-cyclodextrin/Au NPs/γ-Al₂O₃ nanoparticles,p H,ionic strength and mixing time of nanoparticles and drugs in the system were optimized.Under the optimal conditions,the concentration range of nitrofurazone has a good linear relationship(I_SERS=508.96c+31987.87,c:nmol L^-1,R²=0.996)in the range of 3.33～667.00nmol L^-1.The detection LOD（S/N=3）was 0.373 nmol L^-1.The EF of the system in the detection of nitrofurazone was 2.86×10⁶.The effects of several common interfering substances on the determination of nitrofurazone were studied(K⁺,Mg²⁺,Zn²⁺,Ca²⁺,Cu²⁺,glucose and furazolidone).When the SERS method was used to determine the content of nitrofurazone in chicken and duck samples,no drug residues were found in the samples.In the recovery experiment,the recovery of nitrofurazone samples was between 95.11%and 104.51%.The RSD was between 2.41%and 4.83%（n=5）.