DA和AA在CPB现场修饰碳糊电极上的电化学行为及电分析方法

研究了多巴胺(Dopamine,DA)和抗坏血酸(Ascorbic acid,AA)在裸碳糊电极(Carbon Paste Electrode,CPE)和溴化十六烷基吡啶(Cetylpyrid bromide,CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为。与CPE相比,DA在CPB/CPE上与CPB产生了静电排斥作用,氧化峰电流减小,氧化峰电位正移;AA和CPB产生了静电吸引作用,氧化峰电流增大,氧化峰电位负移。循环伏安法研究表明,在DA和AA共存体系中,DA和AA的氧化峰电位相差约340 mV,以此建立了DA和AA的电化学同时测定方法。微分脉冲伏安法研究结果表明,DA和AA氧化峰电流和其相应浓度在1.0×10-5~5.0×10-3mol/L的范围内呈良好的线性关系。本方法也可用于DA和AA共存体系中选择性测定DA。在100倍AA共存时DA的检出限为2.0×10-6mol/L,CPB修饰碳糊电极直接用于市售针剂中DA含量的测定,所得结果令人满意。     

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

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。     

尿酸和抗坏血酸在CPB现场修饰碳糊电极上的电化学行为

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。     

聚亚甲基蓝修饰金电极对过量抗坏血酸存在下尿酸的测定

研究了亚甲基蓝(MB)聚合物膜修饰金电极(PMB/Au)的电化学行为,通过电化学阻抗谱图对其进行了表征,并研究了抗坏血酸(AA)和尿酸(UA)在PMB/Au上的电化学行为.研究结果表明,在PBS水溶液中AA和UA在PMB/Au上的氧化峰电位均负移,峰电流增大,表明PMB/Au对AA和UA电化学氧化反应均产生了催化作用.微分脉冲伏安法(DPV)研究结果表明,在AA和UA共存体系中,AA和UA的氧化峰电位相差约430 mV．以此建立了AA和UA的电化学选择性测定方法.在1.0 mmol·L-1AA共存体系中UA氧化峰电流与其浓度在5.0×10-6～8.0 × 10-3mol·L-1范围内呈良好的线性关系.在500倍AA共存时UA检出限为1.0 靘μmol·L-1,PMB/Au可直接应用于人体尿样中UA的测定,结果令人满意.     

电还原柠嗪酸修饰电极对多巴胺和尿酸的电化学性质研究

采用循环伏安法制备了电还原柠嗪酸膜修饰碳糊电极(ECA/CPE),研究了多巴胺(DA)在该修饰电极上的电化学行为。在pH 7.0的磷酸盐缓冲溶液中,ECA/CPE对DA具有明显的电催化作用,且DA呈现出一对准可逆的氧化还原峰,其氧化峰电流与DA浓度在3.7×10-7~8.2×10-5mol/L和1.04×10-4~9.34×10-4mol/L范围内呈良好的线性关系,检出限为1×10-7mol/L(S/N=3)。使用微分脉冲伏安法,DA和尿酸(UA)在ECA/CPE上的氧化峰能完全分离,且峰电流与浓度呈良好的线性关系。该电极可用于盐酸多巴胺针剂中DA的测定以及人体尿液中UA的检测。     

多巴胺在聚钙羧酸膜修饰碳糊电极上的电催化及与尿酸的同时测定

采用循环伏安法(CV)制备了聚钙羧酸(PCCA)膜修饰的碳糊电极(CPE)。考察了电极对多巴胺(DA)、尿酸(UA)的电氧化催化性能。结果显示,聚钙羧酸膜修饰碳糊电极(PCCA/CPE)对DA有良好的电催化效果,DA呈现出一对准可逆的氧化还原峰,氧化峰电流与DA浓度在3.0×10-7～1.0×10-4mol/L范围内呈线性关系,检出限为1×10-7mol/L(S/N=3)。使用微分脉冲伏安法(DPV),DA和UA在PCCA/CPE上的氧化峰能完全分离(ΔEp=192 mV),且峰电流与浓度均呈现良好的线性关系,可实现对DA和UA的同时测定。实验还进行了实际样品测定。     

PCA/GC电极同时测定尿酸(UA)和抗坏血酸(AA)

制备聚肉桂酸(PCA)修饰电极(PCA/GC),研究尿酸(UA)和抗坏血酸(AA)在该电极上的电化学行为.结果表明,在UA和AA共存体系中,UA、AA在PCA/GC电极上氧化峰电流增大且峰电位分别负移至50mV、330mV,二者相差280mV,据此可同时检测UA和AA.在pH6.0磷酸盐缓冲液中,UA、AA的氧化峰电流与其浓度分别在2.0×10-6～1.0×10-4mol·L-1、2.0×10-5～6.0×10-4mol·L-1范围内呈线性关系.该电极重现性好,适用于尿样中UA的检测.     

亚硫酸盐在乙酰二茂铁修饰碳糊电极上的电催化氧化及其电化学动力学性质研究

研究了亚硫酸盐在乙酰二茂铁(AFc)修饰碳糊电极(AFc/CPE)上的电催化行为。研究结果表明,其在裸碳糊电极(CPE)上的行为比亚硫酸盐在AFc/CPE上的氧化峰电流增加约3倍,氧化峰电位负移360 mV,表明AFc/CPE对亚硫酸盐的电化学氧化具有良好的催化作用。用循环伏安法、计时电流法测定了亚硫酸盐在AFc/CPE上的电极过程动力学参数,测得电荷传递系数α为0.70,电催化氧化反应速率常数k为(4.91±0.05)×104(mol/L)-1.s-1。催化氧化峰电流与亚硫酸盐在5.0×10-4~1.1×10-2mol/L浓度范围内呈良好的线性关系,线性回归方程为Ipa(μA)=1.345 7.956c(10-3mol/L),R=0.9988,检出限为2.0×10-5mol/L。可用于亚硫酸盐的电化学定量测定方法。     

羟苯磺酸钙在溴代十六烷基吡啶自组装膜现场修饰碳糊电极上的电化学行为及应用

研究了羟苯磺酸钙(Calcium Dobesilate,CD)在溴代十六烷基吡啶(Cetylpyridinium Bromide,CPB)自组装膜现场修饰碳糊电极(CPB/CPE)上的电化学行为和电化学动力学性质。实验结果表明,在磷酸盐缓冲液(PBS)中CD在CPB/CPE上的氧化还原峰电流增加,氧化峰电位正移,还原峰电位负移,CPB/CPE对CD电化学氧化还原过程产生促进作用。用方波伏安法(SWV)考察了氧化峰电流与CD浓度的关系,结果表明CD氧化峰电流与其浓度在1.8×10-7~1.0×10-4 mol·L-1范围内呈良好的线性关系,相关系数r为0.9955,检出限(S/N=3)为8.0×10-8 mol·L-1,相对标准偏差(RSD)为1.9%~2.2%,回收率为99.4%~102%。     

芦丁在多壁碳纳米管修饰碳糊电极上的电化学行为及其与DNA的相互作用

采用循环伏安法、微分脉冲伏安法研究了芦丁在多壁碳纳米管修饰碳糊电极(MWCNTs/CPE)上的电化学行为。实验发现,在pH=3.21的Na_2HPO_4-柠檬酸缓冲溶液中,芦丁在0.508V和0.438V产生一对明显的氧化还原峰,氧化峰电流与芦丁浓度在5.0×10~(-7)~2.0×10~(-4) mol/L内呈良好线性关系,检出限为2.0×10~(-7) mol/L。进一步的研究发现芦丁在修饰电极上的反应是受吸附控制的2质子、2电子反应过程;当DNA加入到芦丁溶液后,引起芦丁电化学信号逐渐降低,峰电位逐渐正移,表明两者是通过嵌插作用相结合。     

Electrosynthesis of lactic acid and 2,3-dimethyltartaric acid from pyruvic acid on lead cathode in aqueous medium

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.     

在线扫集-胶束毛细管电动色谱法测定扛板归中的阿魏酸、咖啡酸和原儿茶酸

采用在线扫集-胶束毛细管电动色谱法(sweeping-MEKC)分离测定扛板归中的阿魏酸、咖啡酸和原儿茶酸。采用未涂层熔融石英毛细管(50 cm×50μm,有效柱长36 cm);环境温度25℃;缓冲体系为20 mmol/L NaH2PO4-80mmol/L十二烷基磺酸钠(SDS)-12.5%乙腈(V/V)(pH 2.20),紫外检测波长为216 nm,运行分离电压-20 kV,进样时间100 s。在优化条件下,3种有机酸均在20 min内出峰,峰面积RSD均小于5%。检出限分别达到98.52,118.73和27.27μg/L。     

Convenient and chromatography-free partial syntheses of maslinic acid and augustic acid

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%).     

食品中苯甲酸和山梨酸的气相色谱法分离分析

用毛细管气相色谱法对食品中的防腐剂苯甲酸和山梨酸进行了分离分析。样品用乙醚萃取，萃取物蒸发至干，残渣用氯仿溶解后直接进行色谱分析，FFAP石英毛细管柱，柱温220℃，邻苯二甲酸二甲酯为内标物。两种化合物在0.25mg/mL-4.00mg/mL范围内具有良好的线性关系。     

HPLC法测定脂质体松萝酸中松萝酸的含量

建立了HPLC测定脂质体松萝酸中药物松萝酸的方法。以Kromasil C18反相色谱柱(250 mmⅹ4.6 mm,5μm)为分离柱,流动相组成为V(甲醇)∶V(磷酸盐缓冲液(pH 5.0))=7∶3,流速1 mL/min,紫外检测,波长284 nm。松萝酸在10~50μg/mL的范围内有很好的线性关系(r=0.9994)。加样回收率为100.1%±0.6%,RSD为0.54%±0.07%。本方法适用于脂质体松萝酸中药物松萝酸的测定。     

Determination of oleanolic acid and ursolic acid in cornel by cyclodextrin-modified micellar electrokinetic chromatography

A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was established for the determination of oleanolic acid and ursolic acid in cornel. The two components were separated in the running buffer of 40 mmol/L sodium borate containing 5% methanol, 25 mmol/L SDS and 15 mmol/L hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The applied voltage was 24 kV. The wavelength of detection was 200 nm. The temperature was kept at 25 C. Cinnamic acid was used as the internal standard. The analytical performance of the method was tested with respect to linearity, precision and recovery. The calibration curves were linear in the range of 10.15-243.6 microg/mL, r=0.9993 (oleanolic acid) and 10.07-241.7 microg/mL, r=0.9994 (ursolic acid); the intra-day precision (RSD) was less than 3.7% (oleanolic acid) and 4.1% (ursolic acid); the inter-day precision (RSD) was less than 4.2% (oleanolic acid) and 4.9% (ursolic acid). The limits of detection were 1.6 microg/mL for both components. The method proved to be sensitive, rapid, accurate and suitable for the determination of oleanolic acid and ursolic acid in cornel.     

Synthesis and identification of dinitro- and diaminoterephthalic acid

Dinitroterephthalic acid(DNTPA) and diaminoterephthalic acid(DATPA) were prepared in 85%and 75%yields,respectively. These compounds were characterized by using FTIR and ~1HNMR.DATPA can be used as a monomer for the preparation of polyesters and polyamides.     

Stereoselective synthesis of malyngic acid and fulgidic acid

A new stereoselective total synthesis of malyngic acid has been achieved from a known oxazolidinone derivative via eight steps involving the Evans asymmetric alkylation as the chirality-inducing step and chelation-controlled Zn(BH₄)₂ reduction of an α-hydroxy ketone intermediate for the installation of the 12,13-anti stereochemistry. Fulgidic acid, the C12-epimer of malyngic acid, has also been synthesized in eight steps from the same starting material by using syn-selective K-Selectride reduction of an α-alkoxy ketone intermediate.     

Synthesis and characterization of poly(succinimide-co-6-aminocaproic acid) by acid-catalyzed polycondensation of L-aspartic acid and 6-aminocaproic acid

The polycondensation of L -aspartic acid ( ASP ) with 6-aminocaproic acid ( ACA ) using o-phosphoric acid produced poly(succinimide-co-6-aminocaproic acid). The yield of the MeOH-insoluble copolymer decreased from 99 to 52% and that of the MeOH-soluble one increased from 9 to 47%, with increasing molar ratio of ACA in the monomer feed. The compositions of the succinimide ( SCI ) unit in the MeOH -insoluble and -soluble copolymers tended to be higher than those of ASP in the monomer feed. The copolymers with the 35 mol % SCI units or above were soluble in DMSO , DMF , and conc- H₂SO₄ , but those with the 20 and 21 mol % SCI units were soluble only in conc-H₂SO₄. The melting temperature appeared for the copolymers with less than 76 mol % SCI units. Poly(succinimide-co-6-aminocaproic acid) was easily hydrolyzed to yield poly(aspartic acid-co-6-aminocaproic acid), and it exhibited biodegradability toward activated sludge. © 1997 John Wiley & Sons, Inc.     

Peroxidase based biosensors for the selective determination of D,L-lactic acid and L-malic acid in wines

A novel bioelectrochemical method for the direct determination of D(−) L(+) lactic acid and of L(−) malic acid in wines is presented. Multienzymatic biosensors were realized for the selective determination of the three analytes: D(−) and L(+) lactic acid were measured by a trienzymatic biosensor based on the catalytic activities of the enzymes L(+) lactate oxidase (LOD), D(−) lactate dehydrogenase (D-LDH) and horseradish peroxidase (HRP); L(−) malic acid was measured by a bienzymatic electrode, realized by coupling the enzymes L(−) malic dehydrogenase (L-MDH) and horseradish peroxidase (HRP). In both cases the enzymes were immobilized on an oxygen selective Clark electrode.The simultaneous determination of the two organic acids can be accomplished either in batch or in a flow injection analysis apparatus using the same biosensors as detectors. The analytical performance of the method, tested in standard aqueous solutions and on real samples of wines, showing high repeatability, short response times and reduced cost of analysis, suggest that the experimental approach here described could be followed to monitor the progress of malolactic fermentation.