Rapid Detection Of Paraquat In Fruits And Vegetables Based On SERS Technology

In recent years,Surface-Enhanced Raman Scattering(SERS)technology has been widely used in rapid detection of food safety.Its detection capabilities cover items such as abuse of food additives,pesticide residues/animal residures,and illegal addition of Western medicine in health products.A number of local and industrial standards have been issued.This study reviewed the accuracy and practicality of the detection method in"SN/T4698—2016 Raman Spectroscopy for the Determination of Paraquat in Exported Fruits and Vegetables".Although there is something worth learning,the industry-standard method still has the status quo of complicated operation,poor practicability,and large interference from the sample matrix.Grassroots food and drug testing institutions and industrial enterprises have always had a strong demand for rapid detection of pesticide residues such as paraquat.Therefore,based on a rapid sample pretreatment technology for agricultural products detection(QuEChERS)and an improved Solid Phase Extraction(SPE)technology,this paper made a revolutionary optimization of the pretreatment method.Combining with the above two technologies,a new sample pretreatment technology was proposed,and a rapid detection method for paraquat in import and export vegetables and fruits based on Raman spectroscopy technology was established.The handheld Raman spectrometer was used in the actual sample detection process,which can detect batches of samples quickly without the aid of external power supply.The main content of this research is the following 4 parts:1.The industry standard test method of paraquat was reviewed and demonstrated.According to the detection method in "SN/T Raman Spectroscopy for the Determination of Paraquat in Exported Fruits and Vegetables",the detection results of several fruits and vegetables declared in the standard were rechecked.The results showed that the detection limit of paraquat in cabbage,cucumber,pear,apple,and grape was 0.5 mg·kg-1,while the detection limit of paraquat in tomato,lettuce,and orange was 1 mg·kg-1,which could not reach the detection limit of 0.01 mg·kg-1,indicating that the practicability of the standard method needs to be optimized.2.Rapid detection of paraquat based on SPE technology.Three pretreatment methods of SPE column with ENVC18,C18,and Oasis WCX reported in literatures were reviewed to detect paraquat in samples.The results showed that the detection limit of paraquat in different kinds of vegetables and fruits was 0.5 mg·kg-1 using the SPE column pretreatment method of ENVC18 and C18.Using the SPE column of Oasis WCX,according to the pretreatment method described in the industry standard SN/T 0293-2014,the detection limit of paraquat is the lowest,which can reach 0.1 mg·kg-1 after the sample was extracted,activated,passed through the column,eluted and tested on the machine.The sensitivity of the results from SPE technology combined with SERS method used to measure paraquat in samples was high,and the detection results were more accurate and feasible than the standard method3.Rapid detection of paraquat based on QuEChERS technology.Based on QuEChERS technology,the pretreatment conditions such as extraction solvent,purification tube formula,and solid-liquid ratio were optimized.The results showed that the optimal pretreatment conditions were as follows:acetonitrile as extraction solvent,Octadecyl Silane(C18):Primary Secondary Amine(PSA)ratio of 1:1,and solid-liquid ratio of 1:5.The optimized method was used to pretreat and detect five kinds of fruits,such as lettuce,apple,cabbage,banana,and pitaya.The sample matrix had little effect on the detection.The detection limit of paraquat in the selected fruits and vegetables could reach 0.01 mg·kg-1.indicating that the detection results were ralatively ideal.Compared with the industry standard method and SPE technology,the rapid detection method of paraquat using QuEChERS technology combined with SERS method has lower detection limit,higher sensitivity,and more accurate and feasible4.Establishment of an on-site rapid detection method for paraquat.A simplified pretreatment method based on QuEChERS technology was proposed,using acetonitrile as the extraction solvent,a Cis:PSA ratio of 1:1 as the purification filter tube,and using disposable syringe and organic filter head for filtration.The results showed that the detection limit of paraquat reached 0.01 mg·kg-1,which reached the same level as the detection limit of QuEChERS technology.Three concentration samples were selected for verification,and the quantitative error was less than 5%.This method can extract the extract quickly,and the sample does not need to be centrifuged,which saves time-consuming and power consuming operations such as centrifugation.It can realize the rapid detection of paraquat in a variety of substrates in the field,and has strong practicability.