Study On Methods Based On Surface-enhanced Raman Scattering For Detection Of Benzo[a]pyrene And Acrylamide In Foods

Benzo[a]pyrene and acrylamide are highly toxic substances in food,with strong carcinogenicity,mutagenicity,teratogenicity,neurotoxicity,osseotoxicity,embryonicity and genetic toxicity,and can cause great damage to human body after ingestion.Therefore,many countries and organizations have set strict limits for benzo[a]pyrene and acrylamide content in foods.In order to realize the trace detection of benzo[a]pyrene and acrylamide in food,it is urgent to develop convenient,fast and sensitive detection methods.Surface-enhanced Raman scattering（SERS）is a vibration spectrum technique that achieves high sensitive detection of low concentration analytes through electromagnetic field generated by local surface plasmon excitation.The SERS technology has unique advantages in the field of food detection,such as fast analysis speed,high detection sensitivity and without interference from water phase.In this study,two different composite SERS substrates were used to establish two highly sensitive SERS sensor methods for benzo[a]pyrene and acrylamide in foods,respectively.The main research contents and results are as follows:（1）A SERS method for detecting benzo[a]pyrene based on gold nanostars@reduced graphene oxide（Au NS@rGO） In this study,a simple and sensitive SERS sensor based on Au NS@rGO was successfully developed for the detection of benzo[a]pyrene in foods.The detection strategy is to adsorb benzo[a]pyrene onto the RGO and bring it close to gold nanostars,Then the abundant electromagnetic fields generated by the gold nanostars under laser irradiation,which greatly amplified the Raman signals of benzo[a]pyrene,very high sensitivity for the target analyte was achieved.Different from the traditional methods of detecting benzo[a]pyrene,this SERS mode does not need to modify the functional groups adsorbing benzo[a]pyrene molecules on the surface of SERS substrates,avoiding the phenomenon of the SERS signal of benzo[a]pyrene may overlap with the SERS signal of the introduced functional moieties.Moreover,the particle size,morphology,ultraviolet absorption peak and structures for materials were characterized by ultraviolet-visible absorbance spectrum,Raman spectrum,Fourier-transform infrared spectrum and transmission electron microscope.The synthesis of Au NS@rGO,volume ratio of Au NS@rGO to benzo[a]pyrene standard solution and incubation time were optimized.Under optimized conditions,the SERS sensor exhibited a wide linear detection range(0.1-10000μg L^-1)for benzo[a]pyrene,with the low limit of detection(0.0028μg L^-1).In the anti-interference test,the Raman intensities of benzo[a]pyrene at 611 cm^-1 were 92.23%-99.28%of those in the absence of interferences.The recoveries of chicken samples spiked with benzo[a]pyrene were 89.20%-100.8%.The contents of benzo[a]pyrene in roast mutton and wheat flour samples were determined by SERS sensor and RP-HPLC with similar results,indicating that the SERS sensor method had a good applicability.（2）A SERS method for the detection of acrylamide based on Au@AgNPsIn this work,core-shell Au@Ag nanoparticles was prepared to construct SERS sensor for detecting acrylamide in food.The Au@AgNPs SERS substrate had more uniform particle size and better SERS activity than silver nanoparticles of the same size.The particle size,morphology,ultraviolet absorption peak and elementary composition for materials were characterized by ultraviolet-visible absorbance spectrum,transmission electron microscope and energy-dispersive X-ray spectrum.The synthesis of Au@AgNPs and the volume ratio of Au@AgNPs to acrylamide standard solution were optimized.Under optimized conditions,SERS sensor had a wide linear detection range(10^-8 mol L^-1-10^-3 mol L^-1),and the limit of detection was 1.27×10^-9 mol L^-1 for the acrylamide.In addition,the reproducibility and anti-interference performance of the method were evaluated.The relative standard deviation of the Raman intensities of acrylamide at 1272 cm^-1 was 3.70%in six-times repeated experiments,and the variation in Raman intensities in the presence of interferences was less than 9%.The recoveries of cookies spiked with acrylamide were 85.68%-102.50%using the Au@AgNPs sensor.The SERS sensor method and HPLC method were used to quantify the content of acrylamide in potato chips,fried dough twist and instant coffee samples.There was no significant difference between the results of the two methods.