Study On The Improvement Method Of Sensitivity By Miniaturized Electrophoresis Coupled With Electrochemical Detection

1.IntroductionDue to its advantages of high separation efficiency,small amount of sample required etc.,capillary electrophoresis,as one of the most widely-used separation technologies after liquid chromatography,has been widely applied in biological analysis,food analysis,pharmaceutical analysis and so on.This chapter introduces the principles and devices of capillary electrophoresis,sample derivation techniques and the progresses of new type carbon materials used in this field.In this paper,the methods of improving the sensitivity of amperometric detection have been discussed on the basis of predecessors.On the one hand,based on the mechanism of electrochemical derivatization,2-thiobarbituric acid with strong electroactivity was used as the derivation reagent to react with weak electroactive N-acetylneuraminic acid,and the moving chemical reaction boundary technology was also used for analyte preconcentration to achieve the sensitive electrochemical detection of N-acetylneuraminic acid in salivary.On the other hand,from the perspective of the working electrode,graphene-gold nanocomposite was prepared for the sensitive detection of small molecule amine compounds.2.Electrochemical determination of salivary N-acetylneuraminic acid by miniaturized capillary electrophoresis coupled with sample stackingDue to their important biological role as markers for different pathologies,sialic acid analyses are of great significance in clinical research,in which N-acetylneuraminic acid(NANA)is the main form in human body.In this work,a miniaturized capillary electrophoresis with amperometric detection(mini-CE-AD)was developed for the determination of N-acetylneuraminic acid on the basis of electrochemical derivatization.NANA was first oxidized by periodic acid in an acidic solution,and then the oxidation product ?-formyl pyruvic acid was derived with electroactive 2-thiobarbituric acid(TBA)to form an electroactive NANA-TBA adduct,which could be readily determined by mini-CE-AD after appropriate dilution with NaOH solution.The LOD of NANA-TBA could achieve 0.50?g/mL(1.6?M,S/N=3)based on an online enrichment approach of moving chemical reaction boundary.The proposed method was successfully applied for the analysis of NANA in human saliva,and the recoveries were in the range of 91.8-109%with RSDs of 1.8-3.9%.Due to its simple design and construction,low cost and portability,the mini-CE-AD device should lead more practicability in more field work as an alternative to conventional and microchip CE approaches.3.Electrochemical determination of small molecules amines by miniaturized capillary electrophoresis base on graphene-gold nanoparticle composite electrodeIn this work,a novel graphene-gold nanoparticle composite was prepared by using sodium citrate as a reductant with the in situ chemical reaction.It was mixed with paraffin oil and packed into one end of a fused silica capillary to fabricate composite working electrodes for the sensitive detection of amines.The morphology and structure of the graphene-gold nanoparticle composite were investigated by scanning electron microscopy,X-ray diffraction,and Fourier transform-infrared spectroscopy.The results indicated that gold nanoparticles with an average diameter of 12.8 nm were successfully deposited on graphene to form a well interconnected hybrid network.The analytical performance of these graphene-gold nanoparticle composite working electrodes was demonstrated by separating and sensing two biogenic amines coupled with mini-CE-AD system.The advantages of the composite detectors include higher sensitivity,satisfactory stability and surface renewability,which can be applied in more fields.