Study On Rapid Detection Of Capsaicin On Gutter Oil Based On Surface Enhanced Raman Spectroscopy Technique

Edible oil is a necessity in daily life.However,many illegal businessmen mix gutter oil into edible oil in order to make huge profits,which not only seriously disrupt the market orders,but also directly threaten the life and health of consumers.Gutter oil contains aflatoxin,benzopyrene and other strong carcinogens,which could cause cancers in many parts of the body with long-term consumption.Pepper is one of the most widely used seasonings in the catering industry,and capsaicin,existing in peppers,is the main chemical component that causes spicy taste.Capsaicinoids have the characteristics of strong fat solubility,good stability and high boiling point,which is difficult to completely remove from gutter oil with existing technologies.And almost all kitchen waste oils that have been in contact with capsicum will contain this ingredient.Therefore,capsaicin could be used as an important exogenous characteristic index to identify gutter oil.Although the instrumental detection methods of capsaicin（chromatography,mass spectrometry）have high accuracy and are used as national standard detection methods,they have some disadvantages,such as high price,complex operations,time-consuming,professional technicians need,and toxic reagents addition.Meanwhile,they cannot meet the requirements of quick and simple detection of waste oil in the market.Therefore,it is necessary to study the rapid detection method of capsaicin,so as to quickly identify gutter oil.In recent years,the Surface Enhanced Raman spectroscopy（SERS）technology has been widely used in the quantitative analysis of toxic and hazardous substances in agricultural products due to its advantages of high sensitivity,short signal response time,small amount of samples required,and insensitivity to water.Therefore,this study developed a series of rapid and sensitive detection methods for identifying capsaicin in gutter oil based on SERS technology,in order to make up for the lack of existing detection technologies.The specific content is as follows.A‘two-step’magnetic molecular imprinting-SERS specific detection system was constructed.Magnetic halloysite nanoparticles（MHNTs）were prepared by loading magnetic nanoparticles on the surface of purified natural halloysite nanotubes（HNTs）.Taking MHNTs as a support carrier,capsaicin as a template molecule,acrylic acid（MAA）as a functional monomer,azo Diisobutyronitrile（AIBN）as the initiator,ethylene glycol dimethacrylate（EGDMA）as the cross linker,magnetic molecularly imprinted polymer（MHTs-MIPs）with specific recognition function for capsaicin were synthesized by surface imprinting technique using N,N-Dimethylformamide（DMF）as the solvent.The capsaicin detection system was established by applying MHNTs-MIPs as a material for capsaicin specific separation and taking the synthesized silver nanoparticles and gold nanoparticles as Raman enhancement materials.The results showed that the detection range of this system for capsaicin was 0.05～100μM,and the detection limit was 67.7 n M,and the recovery of capsaicin in simulated gutter oil and actual gutter oil samples were 95.5%～101.3%and 96.3%～100.46%respectively.Moreover,the detection results of this method were in good agreement with the result obtained by HPLC,which indicated that this detection system can be used for the quantitative determination of capsaicin in gutter oil.A colorimetric/SERS dual-modal capsaicin detection system was constructed.The sea cucumber-like Au@Pt nanoparticles were used as the hydrogen peroxide mimic enzyme for colorimetric detection and the Raman enhancement material for SERS analysis.H₂O₂-TMB with obvious color change was used as the colorimetric detection system,and the oxidation product ox-TMB characteristic ultraviolet absorption spectrum and SERS spectrum were used for quantitative analysis with different capsaicin concentrations.The results showed that the colorimetric detection range was1～10000μM,and the detection limit of the quantitative analysis using ultraviolet-visible absorption spectroscopy was 3.48μM,and the detection range of SERS spectroscopy was 10^-9～10^-5 M,and the detection limit was 7.38 n M.This detection system was applied for the detection of capsaicin in simulated gutter oil samples and actual gutter oil samples,of which showed the recoveries of capsaicin were96.48%～102.93%and 91.47%～101.16%by colorimetry,and 95.78%～100.78%and98.75%～102.05%by SERS,respectively.The test results were in good agreement with the result obtained by HPLC,which indicated that this detection system can be used for the quantitative detection of capsaicin in gutter oil.A capsaicin detection system based on diazo coupling reaction and SERS was constructed.4-ATP was used as the diazo coupling material to form an azo intermediate with sodium nitrite in acidic conditions,and then azo intermediate reacted with capsaicin in alkaline condition to form azo compound.The seed growth method was used to synthesize gold nanorods with regular shapes and uniform sizes.The generated azo dye and gold nanorods were mixed and incubated,then was dropped on a pure silicon wafer to collect SERS spectra.The analysis results of collected SERS spectrum showed that the detection range of this system for capsaicin was 10^-4～10^-11 M,and the detection limitation was 3.24×10^-11 M.This method was applied to determine the capsaicin in simulated gutter oil and gutter oil.The recoveries were range from98.44%～103.32%and 97.63%～100.41%,respectively.Moreover,the results were in good agreement with the result obtained by HPLC,which indicated that the detection system can be used for the quantitative detemination of capsaicin in gutter oil.