Facile Separation And Identification Of Food Pollutant Using TLC-SERS On Diatomite Thin Layer Chromatography

Surface Enhanced Raman spectroscopy(SERS)is a sensitive and instant sensing technique that has been widely used in analytical chemistry,environmental protection and food safety.However,the samples in real world usually contain many different components,which makes the identification of analytes from mixed samples very difficult for SERS sensing.The food pollutant was firstly separated by TLC and the corresponding spots of analyte are visualized by iodine colorimetry or fluorescence,and then the analytes were qualitative and quantitative identified by SERS.The main work of this experiment is as follows:1.The combination uses of on-site thin layer chromatography and surface enhanced Raman scattering(SERS)spectroscopy was used to identify polycyclic aromatic hydrocarbons(PAHs)from edible oil samples.Diatomite which is a kind of porous biosilica was used to construct stationary phase on TLC plate,the photonic crystal feature of diatomite is beneficial for SERS enhancement.The highly-porous stationary phase composed of porous diatomite with void shell structure could promote mobile phase interaction with the stationary phase,which leading to improved mass transfer,uniformity and analyte resolution compare with the conventional silica gel plate.The edible oil(1?L)was directly applied to the diatomite plate without pretreatment,and subjected to TLC separation.The polarity of target analytes was calculated for eluent optimization,on which four compounds of PAHs(benzo[a]pyrene,pyrene,anthracene and indeno[1,2,3-cd]pyrene)were successfully separated by using hexane/chloroform(15/1,v/v)as eluent,including compounds with similar polarity(benzo[a]pyrene 0.0477,indeno[1,2,3-cd]pyrene 0.6545,pyrene and anthracene are 0).2?L of Au colloid at 2.4×10^-7 M were transferred onto the diatomite plate for the SERS measurement.The limit of detection was found to be nearly at 0.001 mg/m L.The obtained results can easily identify the four compounds of PAHs in edible oil by their own characteristic Raman peaks.This proposed method provides a simple,instant and effective strategy for on-site identification PAHs from food samples.2.In order to isolate and detect pesticide(carbendazim)residue in real food samples:orange juice and kale leaves.The combination of on-chip thin layer chromatography(TLC)and surface enhanced Raman scattering(SERS)spectroscopy was used for the separating and detecting of carbendazim(MBC)from the complex food sample.The porous stationary phase composed of diatomite biosilica is beneficial for SERS enhancement and eluent migration.The experiments exhibited that the diatomite chip was suitable for TLC separation and has not shown SERS background and provided excellent separation efficiency,10^-8 M silver colloids were appropriate for the SERS measurement on TLC chip.The food sample was directly spotted onto the diatomite chip for TLC separation without any pretreatment.The separation and detection process were finished in less than 5 min,the mixture of pyrimethanil,pymetrozine and MBC could be distinguished simultaneously by TLC-SERS at one diatomite chip.The MBC in orange juice and kale were successfully detected,and a limit of detection(LOD)less than 0.002 mg/m L could be achieved.