Study On Electrochemical Detection Of Rutin,Neurotransmitter,Folic Acid And Other Small Biological Molecules Using Carbon And Carbon-Doped Nanomaterials

Monitoring the content of active ingredients in drugs and neurotransmitters in biological fluids is closely related to human life and health.The common content determination methods are used in the Pharmacopoeia of the People’s Republic of China（2020 edition）including gravimetric analysis,titration analysis,electrochemical analysis,spectrophotometry,and various chromatographic methods.However,due to time-consuming and complicated operation in the actual sample pretreatment process,the application of traditional analytical methods in the field of real-time analysis is limited.Electrochemical analysis is widely applied in drug analysis,medical diagnosis,food safety evaluation,environmental analysis,and other fields due to its advantages of low instrument cost,simple pretreatment operation,sensitivity and fast response.In the process of electrochemical analysis,the part of the sensor is indispensable.The carbon electrode,the sensor platform involved,endows with the merits of the wide potential window,easy availability,and accessibility,including graphite electrode,carbon paste electrode,glass carbon electrode（GCE）,screen printing carbon electrode（SPCE）and carbon fiber electrode（CFE）.The most commonly used working electrode is GCE.GCE has been concentrated for a long time because of its good conductivity and chemical stability,hard texture,and wide polarization range.With the continuous development of science,the appearance of SPCE will integrate the three-electode system of the sensor,simplify and shrink it,so it just needs a slight number of samples to realize real-time analysis.Based on this,the microelectrode can be further reduced,which not only realizes the detection of biomolecules in the external environment,but also can be directly inserted into the cell to realize the monitoring of some secretions in the body.In addition,with the development of materials science,a variety of modified materials have been widely used in the field of electrochemical analysis due to their excellent physical and chemical properties.Carbon materials such as graphite and multiwalled carbon nanotubes（MWNTs）are widely used in electrochemical analysis,contributing to low cost,excellent electrical conductivity,high chemical stability and outstanding biocompatibility.In addition,metal materials with electrocatalytic activity,including lithium cobalt phosphate（LCP）and bismuth oxide,have been focused on enriching electrochemical sensors.Olivine-shape LCP has impressive thermal stability,electrocatalytic activity,and high working potential.The cobalt metal center also provides catalytic sites for electroactive substances.Bismuth oxide nanowires also have the advantages of large surface area and good biocompatibility.According to these,aiming at the detection of electroactive substances in drugs and biological fluids,this paper prepared rapidly and slightly activated graphite electrode and nano carbon doped material modified electrode,and carried out the following three parts of research work:1.Nanometer lithium cobalt phosphate modified electrode for the electrochemical detection of 5-hydroxytryptamine（5-HT）In the experiment,nanoscale LCP was directly used as electrode material,which was supported on the surface of GCE to prepare LCP/GCE,which realized the highly sensitive response to 5-HT.The morphology and structure of LCP were characterized,indicating LCP was successfully prepared.At the same time,the LCP/GCE realized the rapid and sensitive detection of 5-HT in the presence of ascorbic acid（AA）,dopamine（DA）,and uric acid（UA）with the well cathodic peaks separated among them via the differential pulse voltammetry（DPV）cathodic detection method.The cyclic voltammetry（CV）curves of 5-HT was recorded on LCP/GCE surface at different scanning rates,the reaction kinetics of 5-HT on LCP/GCE surface was further studied according to Laviron theory,indicating that the electrooxidation of5-HT on LCP/GCE surface is mainly controlled by adsorption.Kinetic parameters were estimated including electron transfer number（n）and electron transfer rate constant（k_s）.The effect of p H of the background electrolyte on the electrochemical response,the reproducibility and selectivity of the electrode were also investigated.The limit of detection（LOD）of 5-HT was as low as 0.57 nM（3σ/S）under optimal experimental conditions,which was lower than the LOD obtained by reported sensors,and the linear range was from 5 nM～0.2μM.Therefore,the application of LCP/GCE in the highly sensitive determination of 5-HT in practical samples has a certain development prospect.2.Study on the electrochemical response of dopamine,rutin（RT）and paracetaminophen（APAP）by rapidly activated graphite modified electrodeIn this experiment,G/GCE was prepared by fixing graphite powder（G）on the surface of GCE,which was activated with sodium peroxide solution for a few minutes to obtain OG/GCE.The electrochemical response of OG/GCE to DA,RT,and paracetaminophen was significantly improved,and the anode peaks current of OG/GCE was increased by 2.4,4.0 and 2.6 times compared with G/GCE,respectively.The redox peaks of DA,RT and APAP on OG/GCE were well separated.Meanwhile,the electrooxidation kinetics of the three analytes on the OG/GCE surface was studied.The results showed that the electrooxidation of the three analytes on the OG/GCE surface was mainly controlled by diffusion,and the kinetic parameters such as charge transfer coefficient（α）,saturated adsorption capacity（Γ*）and catalytic rate constant(k_cat)were calculated.The linear ranges of DA,RT and APAP were 10.0 nM～10.0μM,1.00 nM～150 nM,and 20.0 nM～30.0μM,respectively.The LODs of DA,RT and APAP were 6.23 nM,0.360nM,and 13.1 nM（3σ/S）,respectively.The content of RT and APAP in the drug were determined by standard addition method,which were consistent with the marked amount.The recoveries of DA in human serum and human sweat were 91.0%～107%,indicating that OG/GCE was a reliable sensor for DA detection in biological samples.In order to verify the practicability of the method,G/SPCE was prepared by loading G on the surface of SPCE,and OG/SPCE was prepared by activation of sodium peroxide.The recovery of DA in human sweat was 91.3%.3.Bismuth oxide nanowires combined with carbon nanotubes modified single carbon fiber electrode for the electrochemical detection of folic acid（FA）The micro-electrochemical device Bi O@CNW/CFE was prepared by in-situ co-electrodeposition of bismuth oxide nanowires（Bi NWs）and multiwalled carbon nanotubes（MWNTs）on the surface of a single carbon fiber electrode（CFE）.In the process of bismuth deposition at-1.1 V,the nanostructure of Bi NWs combine with the MWNTs on the surface of CFE to form Bi O@CNW,and the pine needle nanostructure improve the specific surface area and electrochemical activity of the microelectrode.Based on electrochemical reduction by square wave voltammetry（SWV）,Bi O@CNW/CFE has lower background noise and higher sensitivity for the detection of FA.The linear range of FA was 5.00 nM～200 nM,and the LOD was 0.630 nM（3σ/S）under optimal experimental conditions.The recoveries of FA in human serum and artificial cerebrospinal fluid ranged from 99.0%to 103%,indicating that Bi O@CNW/CFE was a reliable sensor for the detection of FA in biological samples.