共查询到20条相似文献,搜索用时 78 毫秒
1.
用电化学聚合方法制备肉桂酸(CA)修饰的玻碳电极(PCA/GC),研究多巴胺(DA)和抗坏血酸(AA)在修饰电极上的电化学行为.结果表明,在DA和AA共存体系中,DA、AA在PCA/GC电极上氧化峰电流增大且氧化峰电位相差200 mV,据此可同时检测DA和AA.在pH 7.0磷酸盐缓冲液中,DA和AA的氧化峰电流与其浓... 相似文献
2.
丙烯酸十八酯共聚物的结晶和熔融行为研究 总被引:1,自引:0,他引:1
合成了丙烯酸酯(AAn,n为侧链碳原子数)均聚物(PAAn)以及AA18与其同系物的无规共聚物((P(AA18-co-AAn)),并研究了P(AA18-co-AAn)的结晶和熔融行为.结果表明,在AA18与结晶同系物AAn(n=10,12,14,16)的共聚物中,结晶度(Xc)随AA18含量的增加而增大,相应的熔程先增加后下降,存在一个最大值;P(AA18-co-AA14)和P(AA18-co-AA16)的相对结晶度(Xc/Xcmax)受AA18含量影响不大,而P(AA18-co-AA10)和P(AA18-co-AA12)的Xc/Xcmax随AA18含量增加先下降后上升;随着AA18与共聚组份侧链碳原子数差别的增大,熔程的最大值明显增加.在AA18与非结晶同系物AAn(n=4,6,8)的共聚物中,Xc和Xc/Xcmax值随AA18含量的增加而增大,而Xc/Xcmax值随AAn侧链碳原子数的增加而减少,共聚物熔程的最大值差别不大. 相似文献
3.
《分析科学学报》2015,(5)
本研究利用氮掺杂三维石墨烯/血红蛋白(3D N-RGO/Hb)修饰的玻碳电极,实现对食品中丙烯酰胺(AA)的电化学快速检测。以3D N-RGO作为玻碳电极上电子传递材料,利用其疏松多孔、吸附能力强及电子传输通道多等优势,增强了AA与Hb的相互作用,从而降低Hb的电化学信号,实现对AA的响应。实验采用示差脉冲伏安法(DPV)检测AA,所测得氧化还原峰电位为-350mV,峰电流值随AA浓度增大而逐渐减小。在AA浓度为1.4×10-12~1.4×10-4 mol/L范围内,峰电流强度与AA浓度呈现良好的线性关系(R2=0.9799),检出限(S/N=3)为1.0×10-12 mol/L。研究表明该方法制备的涂层厚度均一且不易脱落,能够实现对实际样品中AA的检测。 相似文献
4.
抗坏血酸和尿酸在胶束体系中的电化学行为及选择性测定的应用 总被引:16,自引:0,他引:16
以玻碳电极为工作电极,在PBS中用循环伏安法研究了抗坏血酸(AA)和尿酸(UA)在胶束体系中的电化学行为。在溴化十六烷基吡啶(CPB)胶束体系中,AA和UA的氧化峰电流增加,峰电位负移;在十二烷基苯磺酸钠(SDBS)胶束体系中,AA和UA的氧化峰电流减小,峰电位正移。在CPB中,AA和UA的氧化峰电位相差约270 mV,以此建立了AA和UA的同时测定方法。用微分脉冲伏安法测定AA和UA的氧化峰电流分别在1.0×10-6~1.0×10-2mol/L和5.0×10-7~1.0×10-3mol/L的范围内与各自的浓度范围呈良好的线性关系。在200倍AA共存时UA的检出限为5.0×10-6mol/L。此方法可应用于人体尿样中UA的测定,结果令人满意。 相似文献
5.
用同轴静电纺丝制备了含有稀土铕配合物(Eu(TTA)3AA)的芯-壳结构的丁腈橡胶/聚乙烯吡咯烷酮(NBR/PVP)超细荧光纤维。考察了在外层PVP纺丝参数不变的情况下,改变芯层丁腈橡胶纺丝液的纺丝速度、Eu(TTA)3AA含量等对纤维形貌的影响。通过研究Eu(TTA)3AA-NBR/PVP同轴超细纤维中Eu(TTA)3AA微观结构、含量与纤维的荧光性能之间的关系,发现在同轴纤维形成过程中由于溶剂的快速挥发可使Eu(TTA)3AA形成无定形结构,进而在纤维中形成分子簇级别的分散,在Eu(TTA)3AA含量为30%时,同轴纤维比Eu(TTA)3AA粉末的荧光强度提高了2倍。 相似文献
6.
研究了尿酸(UA)和抗坏血酸(AA)在裸碳糊电极(CPE)和溴化十六烷基吡啶CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为,研究结果表明在PBS(pH=6.8)缓冲溶液中,UA和AA在CPE和CPB/CPE电极上的氧化均为一不可逆过程,在CPB/CPE上UA和AA的氧化峰电位负移,氧化峰电流增大,CPB/CPE对UA和AA的电化学氧化产生了促进作用。用电化学方法测得了UA和AA在CPE和CPB/CPE上的动力学参数如电荷转移系数α,扩散系数D,反应级数和反应速率常数k1。 相似文献
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过氧化氢-亚甲蓝动力学光度法测定亚硝酸根 总被引:6,自引:0,他引:6
1 引 言亚硝酸盐作为食品添加剂以及工业废弃物进入生物圈 ,与仲胺反应生成具有致癌作用的亚硝胺。过多地摄入亚硝酸盐 ,会引起正常血红蛋白 (Fe2 + )转变成铁血红蛋白 (Fe3+ )而失去携氧功能 ,导致组织缺氧。因此 ,卫生和环保部门对亚硝酸盐的使用和排放都作了严格规定。测定亚硝酸盐的常用方法为Griess法。近来研究过的方法还有荧光光度法、重氮化偶联光度法、试剂与亚硝酸根亚硝化光度法、催化褪色法、流动注射法、压电频移法以及双波长叠加分光光度法和化学发光法等。我们在实验中观察到 ,在盐酸介质中 ,亚硝酸根对亚甲蓝… 相似文献
9.
结合金属有机多面体的高催化活性和抗坏血酸的还原性建立了一种简单、高灵敏的抗坏血酸(AA)可视化检测方法。采用铜离子-有机多面体纳米棒(Copper metal-organic polyhedra nanorods,Cu-MOP)作为类辣根过氧化物酶,在H2O2存在下,Cu-MOP催化氧化3,3′,5,5′-四甲基联苯胺(TMB),检测液中存在的AA使Cu-MOP中的Cu2+还原,类辣根过氧化物酶催化活性大大降低,抑制Cu-MOP对TMB的催化氧化,因此,可以利用检测液颜色及其吸光度实现对AA的特异性检测。AA的浓度在1.0~30.0μmol/L及40.0~200μmol/L范围内与体系452 nm的吸光度(A452 nm)呈线性关系,检出限(S/N=3)为0.68μmol/L。本方法简单、快速、无需复杂仪器,将其应用于药品中AA的测定,结果令人满意。 相似文献
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11.
The effect of cationic (cetylpyridinium bromide and cetylpyridinium chloride) anionic (sodium dodecyl sulfate and lithium
dodecyl sulfate) and non-ionic (Brij-35 and Triton-X-100) micelles on the acid-catalyzed hydrolysis of N-phenylbenzohydroxamic
acid in 20 vol.% dioxane medium has been investigated. The kinetic results are explained by both pseudo-phase and Piszkiewicz
cooperativity models. 相似文献
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From relative integrated intensity measurements of the symmetric stretching vibration of nitrate ion in nitric acid solutions (both HNO
3
/H
2
O and DNO
3
/D
2
O), the mass law concentration quotients, Q
were obtained as functions of concentration. By extrapolation the limiting dissociation constants were estimated to be 24.4 and 15 respectively at 25°C. It is shown that this constant refers to a process in which the ion pair H
3
O+ NO
3
–
is in equilibrium with the dispersed, solvated H
3
O+ and NO
3
–
ions. 相似文献
15.
Isa. Degirmenci Tugba Furuncuoglu Ozaltın Ozlem Karahan Veronique Van Speybroeck Michel. Waroquier Viktorya Aviyente 《Journal of polymer science. Part A, Polymer chemistry》2013,51(9):2024-2034
In this study, the relative rate of polymerization of acrylic acid (AA) versus methacrylic acid (MAA) and the effect of water on the polymerization kinetics are investigated within a combined static and molecular dynamics set of computational tools. Experimentally the relative rate of propagation of AA versus MAA is around 35 in bulk and 31 in water. Classical Molecular Dynamics calculations have been carried out to determine the location of the solvent molecules in the proximity of the dimeric poly(AA) and poly(MAA) units. A combined implicit/explicit solvent model was used for the evaluation of the kinetics of the dimeric polymer chains. We show that the rate acceleration of both polymers in water is mainly due to entropic rather than electrostatic effects and is in agreement with experimental findings. Moreover the slower propagation rate of MAA versus AA is ascribed to additional steric effects present in MAA due to the methyl group at the α position of the monomer. Among the functionals used, the M06‐2X/6‐311+G(3df,2p)//B3LYP/6‐31+G(d) methodology reproduces the experimental rate constants quantitatively the best. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
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Derivatization yields of different esters (methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl) of citric, malic and isocitric acids with various acylating agents, such as acetic anhydride, propionic anhydride, trifluoroacetic anhydride and heptafluorobutyric anhydride, were investigated. The formation of acylated malic and isocitric acid esters is rapid and quantitative whereas the acylation of citric acid esters was slow and partial in most instances. It was found that selective analytical conditions can be achieved with the O-heptafluorobutyryl n-butyl esters. The analytical applicability of the separation and determination of the malic, isocitric and citric acid contents of model solutions and of pressed lemon juice is discussed. Concentrations of 1.2 × 10?3 ?9.0 × 10?3g per 100 g of isocitric acid and 4.2 × 10?3 ?3.5 × 10?2 g per 100 g of malic acid in the presence of 9.3 × 10?1 g per 100 g of citric acid were measured with relative standard deviations of 7.5 and 4.2%, respectively. 相似文献
18.
A convenient and chromatography-free 4-step synthesis of analytically pure maslinic acid (1, 41.2%) from oleanolic acid has been developed. Slight variations in the final steps gave an excellent yield of isomeric augustic acid (7, 71.9%). 相似文献
19.
C. Martin 《Tetrahedron letters》2006,47(20):3459-3462
Lactic and 2,3-dimethyltartaric acids have been synthesized from pyruvic acid by changing the nature of the supporting electrolyte and the electrode potential of lead cathode. 相似文献
20.
The present work reports a quercetin-modified wax-impregnated graphite electrode (Qu/WGE) prepared through an electrochemical oxidation procedure in quercetin-containing phosphate buffer solution (PBS), for the purpose of detecting uric acid (UA) in the presence of ascorbic acid (AA). During modification quercetin was oxidized to the corresponding quinonic structure, and in the blank buffer solution the electrodeposited film exhibits a voltammetric response anticipated for the surface-immobilized quercetin. Retarding effect of the film towards the reaction of anionic species was found; therefore the pH of sample solutions was selected to ensure the analyte in molecular form. At suitable pHs the Qu/WGE shows excellent electrocatalytic effect towards the oxidation of both AA and UA, and separates the voltammetric signal of UA from AA by about 280 mV, allowing simultaneous detection of these two species. A linear relation between the peak current and concentration was obtained for UA in the range of 1-50 μM in the presence of 0.5 mM AA, with a detection limit 1.0 μM (S/N = 3). This sensor was stable, reproducible and outstanding for long-term use. 相似文献