發(fā)布時(shí)間：2018-09-11 14:33

【摘要】：維生素C(抗壞血酸,簡(jiǎn)稱Vc),是維持機(jī)體正常生命活動(dòng)所必需的一種生物因子。它能夠參與生物體內(nèi)的許多反應(yīng)如促進(jìn)體內(nèi)膠原合成、神經(jīng)遞質(zhì)合成、類固醇及有機(jī)物質(zhì)的羥化。適量的Vc,有助于滿足人體的需要、增強(qiáng)抵抗疾病的能力及降低癌癥發(fā)病率。人體缺乏Vc或攝入過量Vc都會(huì)對(duì)機(jī)體造成不良的影響。同時(shí),Vc含量的變化可以作為判斷果蔬新鮮程度和耐儲(chǔ)藏性的重要指標(biāo)之一,Vc作為抗氧化劑被廣泛用于工業(yè)生產(chǎn)中。因此,建立快速有效的Vc檢測(cè)方法具有重要意義。本研究基于Vc能在電極表面直接發(fā)生氧化反應(yīng)的原理,構(gòu)建電化學(xué)方法用于食品中Vc的快速檢測(cè)。其主要研究?jī)?nèi)容如下:1.電極的選擇:利用玻碳電極(GCE)、自制鉑絲微電極(ME)及自制嵌入式粉末微電極(PME)為工作電極。為提高工作電極的電化學(xué)性能,在電極表面引入經(jīng)混酸液相氧化法處理的納米材料多壁碳納米管(MWCNTs),利用不同的分散劑H2O、N,N-二甲基甲酰胺(DMF)分別制備出不同的修飾電極water/MWCNTs/GCE、DMF/MWCNTs/GCE、DMF/carboxyl/MWCNTs/GCE、water/MWCNTs/ME、DMF/MWCNTs/ME、DMF/carboxyl/MWCNTs/ME。通過形貌表征和電化學(xué)性能測(cè)試優(yōu)選DMF/carboxyl/MWCNTs/GCE、DMF/carboxyl/MWCNTs/ME為最佳電極。在此研究基礎(chǔ)上,將carboxyl/MWCNTs嵌入經(jīng)腐蝕的ME中,制成carboxyl/MWCNTs/PME。2.檢測(cè)條件的優(yōu)化與探究:利用DMF/carboxyl/MWCNTs/GCE、DMF/carboxyl/MWCNTs/ME作為工作電極,對(duì)DMF/carboxyl/MWCNTs修飾液濃度進(jìn)行優(yōu)化。結(jié)果表明,其最優(yōu)修飾液濃度均為1.0×10-3 g/mL。基于循環(huán)伏安法,對(duì)pH的影響進(jìn)行考察,分別得出三種電極DMF/carboxyl/MWCNTs/GCE、DMF/carboxyl/MWCNTs/ME、carboxyl/MWCNTs/PME最優(yōu)pH環(huán)境分別為pH7.0、pH5.0、pH6.0。對(duì)Vc在三種電極表面的反應(yīng)狀態(tài)進(jìn)行探究,結(jié)果表明Vc在DMF/carboxyl/MWCNTs/GCE、DMF/carboxyl/MWCNTs/ME電極表面均受吸附控制影響,在carboxyl/MWCNTs/PME電極表面受擴(kuò)散控制影響。3.在以上研究結(jié)果的基礎(chǔ)上,分別利用DMF/carboxyl/MWCNTs/GCE、DMF/carboxyl/MWCNTs/ME及carboxyl/MWCNTs/PME作為工作電極。其中DMF/carboxyl/MWCNTs/ME、carboxyl/MWCNTs/PME作為工作電極可簡(jiǎn)化三電極系統(tǒng)為兩電極系統(tǒng),對(duì)樣品中的Vc含量進(jìn)行檢測(cè)研究。結(jié)果表明,基于DMF/carboxyl/MWCNTs/GCE電極,Vc的線性響應(yīng)范圍為1.0×10-6~1.0×10-3mol/L,線性方程為Ipa(10-5 A)=0.226c(10-4 mol/L)+1.351,R=0.999,檢出限為2.50×10-7 mol/L,回收率為99%~105%;基于DMF/carboxyl/MWCNTs/ME電極,Vc的線性響應(yīng)范圍為1.0×10-4~2.0×10-1 mol/L,線性方程為Ipa(A)=4.197×10-8+1.273×10-5c,R=0.998,檢出限為1.0×10-5 mol/L,回收率97%~113%;基于carboxyl/MWCNTs/PME電極,Vc的線性響應(yīng)范圍為5.00×10-6~9.50×10-4 mol/L,線性方程為Ipa(μA)=3.259×10-2+1.801×102c,R=0.997,檢出限為4.89×10-7 mol/L,回收率96%~105%。
[Abstract]:Vitamin C (ascorbic acid, abbreviated as Vc),) is a biological factor necessary to maintain normal life activities. It is involved in many reactions in vivo, such as promoting collagen synthesis, neurotransmitter synthesis, steroids and hydroxylation of organic substances. Moderate amount of Vc, helps to meet human needs, increase resistance to disease and reduce the incidence of cancer. Lack of Vc or excessive intake of Vc can cause adverse effects on the body. At the same time, the change of VC content can be used as an important index to judge the freshness and storability of fruits and vegetables. As an antioxidant, VC is widely used in industrial production. Therefore, it is of great significance to establish a fast and effective Vc detection method. Based on the principle that Vc can directly oxidize on the electrode surface, an electrochemical method was constructed for the rapid detection of Vc in food. The main research contents are as follows: 1: 1. Electrode selection: the platinum wire microelectrode (ME) and the self-made embedded powder microelectrode (PME) were used as working electrodes using glassy carbon electrode (GCE),) as the working electrode. In order to improve the electrochemical performance of the working electrode, the multiwalled carbon nanotube (MWCNTs), which was treated by mixed acid solution phase oxidation method, was introduced on the electrode surface to prepare different modified electrode water/MWCNTs/GCE,DMF/MWCNTs/GCE,DMF/carboxyl/MWCNTs/GCE,water/MWCNTs/ME,DMF/MWCNTs/ME,DMF/carboxyl/MWCNTs/ME. by using different dispersant H _ 2O _ N _ (N) N _ (N-dimethylformamide) (DMF). DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME was selected as the best electrode by morphology characterization and electrochemical performance test. On the basis of this research, carboxyl/MWCNTs is embedded in the corroded ME to make carboxyl/MWCNTs/PME.2.. Optimization of detection conditions: DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME was used as working electrode to optimize the concentration of DMF/carboxyl/MWCNTs modified solution. The results showed that the optimal concentration of the modified solution was 1.0 脳 10 ~ (-3) g / mL. Based on the cyclic voltammetry, the influence of pH was investigated. The results showed that the optimal pH environment for DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME,carboxyl/MWCNTs/PME of three electrodes was pH7.0,pH5.0,pH6.0.. The reaction states of Vc on three kinds of electrode surfaces were investigated. The results show that Vc is controlled by adsorption on the surface of DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME electrode and by diffusion control on the surface of carboxyl/MWCNTs/PME electrode. Based on the above results, DMF/carboxyl/MWCNTs/GCE,DMF/carboxyl/MWCNTs/ME and carboxyl/MWCNTs/PME are used as working electrodes respectively. DMF/carboxyl/MWCNTs/ME,carboxyl/MWCNTs/PME as a working electrode can simplify the three-electrode system to a two-electrode system. The content of Vc in the sample is determined. The results show that 鍩轟簬DMF/carboxyl/MWCNTs/GCE鐢墊瀬,Vc鐨勭嚎鎬у搷搴旇寖鍥翠負(fù)1.0脳10-6~1.0脳10-3mol/L,綰挎，

本文編號(hào)：2236967