Establishment Of The Electrochemical Methods For Capsaicinoids And Their Applications

Objective:1.Toestablishasimple,cost-effectiveandunmodified electrochemical method for the determination of capsaicinoids.2.To establish a highly sensitive electrochemical method for the detection of capsaicinoids based on the gold nanoparticle/magnetic ferroferric oxide?AuNPs/Fe₃O₄?nanocomposites and azo reaction,the capsaicinoids were enriched on the surface of screen printed carbon electrode?SPCE?.This method was used to detect the content of capsaicinoids in the illegal cooking oil?ICO?and identify the ICO.Methods:1.Cyclic voltammetry?CV?and differential pulse voltammetry?DPV?were used to analyze capsaicinoids qualitatively and quantitatively.The unmodified SPCE was used,including a graphite working electrode with the diameter of 2.5 mm,a graphite auxiliary electrode and an Ag/AgCl reference electrode.2.The AuNPs/Fe₃O₄ nanocomposites were prepared by high-energy electron beam irradiation.The 4-Aminothiophenol?4-ATP?was immobilized on AuNPs by the Au-S covalent binding to form AuNPs/Fe₃O₄-ATP complex.The illegal cooking oil sample was reacted withAuNPs/Fe₃O₄-ATPbyazoreactiontoform AuNPs/Fe₃O₄-ATP-azo-Caps complex after liquid-liquid extraction.The complex was washed twice with ultra-pure water and then redispersed with supporting electrolyte.An external magnet was used to enrich capsaicinoids in the working area of SPCE.DPV method was used to detect capsaicinoids.Three positive ICO samples and three negative control samplesweredeterminedbyestablishedmethodandliquid chromatography-mass spectrometry?LC-MS?,the results of the two methods are consistentResults:1.Under the optimal experimental conditions,the linear range of capsaicinoids was from 0.16 to 16.37?mol/L,the regression equation was I??A?=0.5737 c+0.5375?R²=0.9978?.The limit of quantification?LOQ?for capsaicinoids was 0.15?mol/L and the limit of detection?LOD?was0.05?mol/L?S/N=3?.The intra-day and inter-day variations were lower than 5.0%and 8.6%,respectively.The average recoveries were ranged from 95.5%to 107.7%.The method was applied to determine the contents of capsaicinoids in five kinds of chilli peppers purchased from the supermarket.2.A highly sensitive electrochemical method for the detection of capsaicinoids was established based on AuNPs/Fe₃O₄ nanocomposite and azo reaction.The linear range of capsaicinoids was from 0.10 to 10.00ng/mL,the regression equation was I??A?=0.8508 c+0.8169?R²=0.9947?.The LOQ for capsaicinoids was 0.05 ng/mL and the LOD was0.02 ng/mL?S/N=3?.The intra-day and inter-day variations were lower than 5.7%and 7.7%,respectively.The average recoveries were ranged from 92.8%to 103.9%.Conclusions:1.A simple,rapid and cost-effective electrochemical method was developed successfully with disposable unmodified SPCE for the quantitation of capsaicinoids.As the SPCE has the potential for miniaturization detections,the developed method provides a promising tool in food industry sector.2.A highly sensitive electrochemical method was developed for the quantitation of capsaicinoids in ICO sample based on AuNPs/Fe₃O₄nanocomposites and azo reaction.This method can identify the ICO and provide a sensitive and inexpensive method for food hygiene.It is of great significance to safeguard the food safety and health of the people.