Determination Of Phenols And Aldehydes On Electro-activated Electrode

Phenols and aldehydes involued in honey’s flavor and used as repellants,accurate detection of phenols and aldehydes in honey,therefore,are of great significance to ensure honey’s quality and authenticity.Phenol molecules and aldehyde molecules contain electroactive groups—hydroxyl（-OH）and carbonyl（-C=O）respectively,which can be reacted and generated current signals under certain potentials.Electro-analysis as a sensitive,simple-operated,cost-effective and eco-friendly method,has shown great potential in food detection.To improve the detection performance of analytes,the modification of working electrode has always been a research hotspot and difficulty.Electro-activation has attracted the attention of researchers due to its mild operating conditions and good reproducibility.However,at present,the research on the change of the sensing interface structure of the electro-activated electrode is lack.Therefore,this paper analyzed the changes of the electrode surface after electroactivated,then studies its influence on the molecular detection of phenols and aldehydes,and finally developed a detection method for phenols and aldehydes in honey.The main research contents and conclusions are as follows:（1）Electroactivate the glassy carbon electrode（GCE）and gold electrode（Au E）in different electrolytes,and analyze the changes in the surface morphology and impedance of the electroactivated electrode by XPS,EDS,XRD and EIS,etc.The effect of activation on the electrode surface and the effect of changes in the electrode surface on analyte detection.The results show that the R_ct of GCE and Au E decreases from 193.9Ω（bare GCE）and191.3Ω（bare Au E）to 32.01Ω（Na OH/GCE）and 39.64Ω（bare Au E）;their surface areas from 0.11 cm²（bare GCE）and 0.14 cm²（bare Au E）increase to 0.49 cm²（Na OH/GCE）and0.15 cm²（KOH/Au E）;the metal ions in the electrolyte such as Na⁺and K⁺will be adsorbed on the electrode surface;C=O increased from 3.78%（bare GCE）to 13.91%（Na OH/GCE）,and the thickness of the oxide layer on the Au E increased by 3.82 times.In addition,the crystal phase of the Au E surface changed significantly,resulting in active sites with crystal defects.（2）Investigating the signal responses of phenols on electro-activated GCE and Au E,so as to develop the electro-activated electrode for detecting phenols.Then,studying the effects of different activation methods,incubation times,and electrolyte p H values on the detection of phenols.The results show that the electro-activated Au E leads to the decrease of the catechol（CC）response signal due to the generation of the surface oxide layer,while the GCE activated in Na OH improves the detection signal of CC most obviously,and available for detecting gallic acid,protocatechuic acid and caffeic acid.After 1 min of incubation,CC performed well in SWV detection technique and p H 7.0 electrolyte.The linear range of Na OH/GCE for CC detection is 0.01-1000μmol/L.The repeatability of electrode preparation is good;the detection limit is 46.23 nmol/L.Under the influence of Na⁺,Cl^-,SO₄^2-,Ca²⁺,Fe³⁺and glucose.The recoveries of Na OH/GCE used for CC detection in honey ranged from 84.00 to 96.54%.（3）Prepare electroactive GCE and Au E in different activation solutions,investigate the the detection signals of aldehydes on electro-activated electrodes,develop an electroactive electrode for detecting aldehydes,and further study aldehydes under different electrochemical detection conditions,such as detection mode,incubation time and electrolyte p H.The results showed that both Au E and GCE activated in alkaline solution responded well to methylglyoxal（MGO）.Compared with bare Au E and bare GCE,the MGO signal after electroactivation increased by 7-fold and 4.5-fold,respectively.Both KOH/Au E and Na OH/GCE have good detection performance for MGO at SWV and p H 9.0,and the linear range of MGO detection with KOH/Au E is 1×10^-6～5×10^-2 mol/L.The detection reproducibility is good;the detection limit is 0.67μmol/L.Under the influence of Na⁺,Cu²⁺,Zn²⁺,Ni²⁺,Mg²⁺and glucose,the response signal of MGO to KOH/Au E remains relatively stable.The recovery rate of MGO in honey detected by KOH/Au E was 86.81～114.72%.The linear detection range of MGO using Na OH/GCE is 5×10^-6～1 mol/L,and the detection limit is 0.41μmol/L.Finally,the recovery rate of MGO in honey detected by Na OH/GCE was 82.84～99.55%.