Study On Rapid Detection Method And System Development Of Thiabendazole Residues In Citrus Based On Surface-enhanced Raman Spectroscopy

Citrus is rich in nutrition and delicious.It is one of the cash crops with wide planting area and high consumption demand in China.Thiabendazole(TBZ),as a benzimidazole pesticide,is widely used in the control of fungal diseases in citrus,which ensures the yield and quality of citrus.However,the use of TBZ has caused problems with pesticide residues in citrus and has attracted national and social attention.Existing methods and systems for detecting pesticide residues suffer from deficiencies such as long detection time,expensive instrumentation,and inability to spot detection.Therefore,in this study,a rapid,sensitive and stable quantitative detection method for TBZ residues in citrus was constructed based on the surface enhanced Raman spectroscopy(SERS)technique,combined with chemometric,and the development of a rapid on-site detection system for TBZ residues in citrus was further carried out based on this method.The details of this study are as follow:1.Development of a rapid label free SERS detection method for TBZ residues in Citrus.In view of the problems of long time,complicated operation and need for biomarkers in traditional detection methods,we carried out a rapid label free SERS detection method for TBZ residues in Citrus based on metal nano SERS substrate combined with chemometrics.First,gold nanorods(Au NRs)were prepared as Raman enhanced substrates by a seed growth method.The prepared Au NRs were mixed with citrus extract at different TBZ concentrations,and their SERS spectra were collected.Then,baseline correction and spectral preprocessing were applied to reduce baseline drift and interference of the original spectrum.Immediately afterwards,a quantitative detection model of TBZ residues in citrus was constructed using different variable screening algorithms combined with partial least squares(PLS)method,respectively.Finally,the performance of the quantitative detection model is evaluated.The results show that the quantitative detection model established by GA variable selecting algorithm combined with PLS has the best performance with Rc~2=0.9834、RMSEC=0.0929、Rp~2=0.9737,RMSEP=0.1179 and RPD=5.85.The proposed method was validated by HPLC method using t-test(P>0.05)with no significant difference in detection result.The research shows that the detection method based on chemometrics combined with SERS technology can realize the rapid and accurate quantitative detection of TBZ residues in citrus,which provides a basis for subsequent field detection applications.2.Development of portable SERS detection system for TBZ residue.In view of the current SERS detection device carrying unchanged,difficult on-site detection and insufficient functions of operating software,based on the SERS detection method of TBZ residue in citrus,a portable SERS detection system is developed.The detection system consists of hardware system and software system.The hardware includes semiconductor laser transmitter,Raman probe,micro Raman spectrometer,control circuit board,Bluetooth serial port module and Android mobile phone.The software is an Android application developed based on Java language.The main functional modules include Bluetooth communication,spectrum acquisition and prediction,and data storage.The portable detection device is small in size,and the Bluetooth communication between software and hardware is normal.The stability of the spectrum collected by the system is analyzed,and the results show that the collected SERS spectra of citrus samples with the same concentration of TBZ(0.5μg/m L)by three times are basically consistent.The study shows that the developed portable SERS spectral detection system can be applied to the on-site detection of TBZ residues in citrus,which is easy to operate and has good stability.3.Construction of a SERS detection web cloud platform for TBZ residue.For the problems of low level of data sharing and difficult model maintenance in portable SERS detection system,a SERS detection Web cloud platform for TBZ residues in citrus was built by using browser/server(B/S)mode to platform management of field terminal devices.First,based on Vue.js,Element UI,Echarts designed the interactive management webpage of the web cloud platform,which can view spectral data and upload detection model through a browser.Then,the processing and storage of detection data were realized using Springboot,Tomact and My Batis.Finally,the wireless network connection of the portable terminal device and the web cloud platform is established through IP and port number,so as to construct a set of TBZ residue SERS detection system in citrus with high information sharing degree and convenient model maintenance.On this basis,10 independent citrus spiked samples were used to verify the performance of the detection system.The results showed that the maximum coefficient of variation(CV)of the 3-fold parallel predictions for the constructed system was found to be 4.96%<5%.The mean relative error between the values detected by the constructed system and HPLC was 2.52%,which was not significantly different.The Web cloud platform composed of portable device can realize the accurate and quantitative detection of TBZ residues in citrus.The research shows that the constructed SERS detection web cloud platform provides the basis for model sharing and spectral data management,reduces the difficulty of model modification and maintenance,and improves the informatization level of TBZ residue SERS detection system in citrus.