| Potassium ion(K+)is essential for healthy physiology and is involved in a variety of physiological and pathological activities,and many diseases such as diabetes and heart disease are significantly associated with imbalances in potassium ion concentrations.In addition,the amount of potassium content in the soil is directly related to the normal growth of plants.Potassium compounds are present in additives in food and beverages,nutrients,and food packaging materials such as cigarette paper in the form of combustion aids.Traditional detection methods such as atomic absorption,ion chromatography,etc.,usually require expensive and bulky equipment that is not convenient for rapid on-site detection.Therefore,developing a small portable sensing platform for potassium detection is important.Ion-selective electrode(ISE)has the advantages of simple fabrication,low cost,and portability,especially the all-solid-state ion-selective electrode(SC-ISE),which is easier to realize the miniaturization and integration of the sensor and has become the development trend of the next generation of sensors.The solid-state conduction layer material of the ion-electron transducer,which is its core part,generally exhibits double-layer capacitance and redox capacitance properties to overcome the ion-electron transport barrier between the conduction layer and the membrane.Currently used to improve the performance of the conductive layer material mainly through two aspects:first,structural regulation,the material has a good conductivity based on a larger specific surface area and hydrophobic properties,which is conducive to the formation of a large double-layer capacitance and try to avoid the appearance of the water layer.Second,component doping,by doping metal nanoparticles,metal oxides,etc.in the matrix material to obtain more electrochemical active sites,gives the material greater capacitive properties or increases its redox properties,so that the sensor performance can be improved.Based on this,a series of allsolid polymer membrane potassium ion-selective electrodes based on hollow carbon nanospheres and their composites were prepared and developed in this paper and applied to the rapid and accurate determination of potassium content in cigarette paper,which is superior to the traditional ionic chromatography and commercial potassium electrodes.The main studies are as follows.1.Construction of hollow carbon nanospheres based on all-solid polymer membrane potassium ion-selective electrodePhenolic resin balls were synthesized from 3-aminophenol and formaldehyde,and after selective removal of inhomogeneous components inside the resin balls using acetone,Hollow carbon nanospheres(HCNS)were obtained after high-temperature carbonization.The hollow carbon nanospheres were uniformly dispersed in tetrahydrofuran,a novel all-solid potassium ion-selective electrode(GC/HCNS/K+-ISM)was made by taking an appropriate amount of HCNS suspension and applying it dropwise on the glassy carbon electrode(GC)and then covering it with a polymeric potassium ion-selective membrane.The microstructure and morphology of the materials were investigated by various characterization experiments.the performance of the GC/HCNS/K+-ISM electrode was verified by electrochemical tests.The experimental results showed that hollow carbon nanospheres(HCNS)are an excellent conductive layer material,and the linear response range of the prepared GC/HCNS/K+-ISM electrode was 5.0×10-6～1.0×10-2 mol/L,the lower limit of detection reached 1.4×10-6 mol/L.The sensor has a fast response speed,high sensitivity,good stability,and reproducibility.In the performance test of the electrode for up to 4 months,the response slope of the electrode decreased by 4.34%compared with the initial value,indicating that the electrode has a long service life,which can reduce the frequent replacement and maintenance during use and reduce the use cost.In the test of actual cigarette paper samples,the average relative deviation from ion chromatography was 4.89%(n=6),indicating that the electrode can be used for the detection of actual samples and has important application prospects.2.Construction of an all-solid-state polymer membrane potassium ion-selective electrode based on ZnCo2O4@HCNSBased on the research foundation of the first work,a simple one-pot method was used to successfully synthesize zinc cobaltate/hollow carbon nanosphere composites(ZnCo2O4@HCNS)using hollow carbon nanospheres as the carrier material.The microstructure and properties of the material were studied through various experimental characterization technques,and a new all-solid-state electrode was successfully prepared by placing the ZnCo2O4@HCNS material between a polymer potassium ion-selective membrane and a glassy carbon electrode conductive substrate(GC/ZnCo2O4@HCNS/K+-ISM).The experimental results of the electrode test show that under optimal conditions,the electrode exhibits a linear response in the range of potassium ion concentration of 1.1×10-6～1.0×10-2 mol/L,and the lower detection limit reaches 5.3 7×10-7 mol/L.The electrode has a fast response speed,good selectivity,and stability.In the electrode performance test experiment for 3 consecutive months,the electrode response slope decreased by 4.01%,indicating that the electrode has good stability.In the test of actual cigarette paper samples,the average relative deviation from ion chromatography was 4.02%(n=6),indicating that the electrode can be used for the detection of actual samples and has important application prospects.3.Construction of an all-solid-state polymer membrane potassium ion-selective electrode based on Mn/Ni-MOF@HCNSBased on the research basis of the first work,Mn/Ni bimetallic organic framework/hollow carbon nanospheres(Mn/Ni-MOF@HCNS)composites were successfully synthesized using hollow carbon nanospheres as the carrier material,and the microscopic characteristics and properties of the materials were explored by characterization.And a new all-solid-state electrode(GC/Mn/Ni-MOF@HCNS/K+-ISM)was successfully prepared by using the Mn/NiMOF@HCNS material as the solid-state conduction layer of the all-solid-state polymer membrane potassium ion-selective electrode,and the performance of the electrode was investigated.The results showed that the electrode exhibited a linear response in the range of 1.0×10-6～1.0×10-2 mol/L of potassium ion concentration under the optimal conditions,and the lower limit of detection reached 3.80×10-7 mol/L.The electrode has a fast response,good selectivity,and stability.In the electrode performance test experiment for 2 consecutive months,the electrode response slope decreased by 2.55%,indicating that the electrode has good stability.In tests on actual cigarette paper samples,the average relative deviation from the ion chromatography method was 3.87%(n=6),indicating that the electrodes can be used for the detection of actual samples and have important application prospects.4、Optimized and realized the rapid detection of potassium content in cigarette paperIn this chapter,a simple and rapid method for the determination of potassium content in cigarette paper was developed using the pK-1-01 potassium ion-selective electrode.By comparing the pretreatment methods of cigarette paper samples,it was found that the extraction of potassium ions by ultrasonic extraction with 1%dilute acetic acid for 30 min was fast,simple,and environmentally friendly.By comparing the potential response behavior of the potassium ion-selective electrode in different buffer solutions,it was found that it has excellent response performance in lithium acetate buffer solution(0.1 mol/L,pH=7.0),with a linear response range of 1.0×10-5～1.0×10-2 mol/L for K+,a linear response slope of 55.79 mV/dec(25℃),and a lower limit of detection up to 2.14×10-6 mol/L.The average relative standard deviations of the K+selective electrode on cigarette paper samples were 0.55%for the intra-day test and 2.8%for the inter-day test,both less than 5%.The test results of the electrode method were in good agreement with that of ion chromatography,with an average relative deviation of 4.1%(n=10)and recoveries between 95.0%and 101.9%.It showed good timeliness during the continuous one-week test,indicating that the method can be well applied to the rapid detection of potassium content in cigarette paper samples.It showed good timeliness during the continuous one-week test,indicating that the method can be well applied to the rapid detection of potassium content in cigarette paper samples.In addition,the three prepared all-solid-state polymer membrane potassium ion-selective electrodes were compared with the pK-1-01 potassium ion-selective electrode,which showed that the performance of the prepared three solid-state potassium electrodes was better than that of traditional potassium electrodes,and has important application value. |
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