碳糊电极的吸附／萃取行为及电化学测定美托托宁

报道了碳糊电极测定吲哚类神经化学物质美拉托宁（ＭＬＴＮ）的灵敏电化学分析方法。该经物在电极上开路吸附／萃取预富集后,进行阳极溶出伏安测定,在０．７０Ｖ附近显示了氧化溶出峰。ＭＬＴＮ在２．０＊１０＾－６－１．０＊１０＾－２ｇ／Ｌ范围内峰电流与浓度呈线性关系,检测限可达１．５＊１０＾－７ｇ／Ｌ。该法具有较强的抗干扰能力,在适当条件下ＶＢ６不干扰ＭＬＴＮ的测定。直接测定片剂中的ＭＬＴＮ含量,平均回收率为９８％。本文了探讨了有机化合物在碳糊电极上的富集和溶出机理,发现碳糊电极对有机药物具有强烈的萃取和吸附作用,计时库仑法研究表明萃取在富集过程中起着主要作用。     

金在碳糊电极上的静电吸附及溶出伏安测定

阳极溶出伏安法测定金具有灵敏度高,操作简便等优点,但共存金属往往干扰测定,影响该方法的应用。为减少干扰,已有阴极溶出伏安法的报道。 作者曾采用修饰了三烷基叔胺的碳糊电极,通过开路萃取富集和介质交换,测定矿样中的金,并且发现,碳糊电极本身能在正电位下直接富集微量金,在阴极溶出伏安法中显示了     

1—（2—吡啶偶氮）—2—萘酚修饰的铅笔芯电极上铜的阳极溶出伏安特性

１引言我们曾用２Ｂ型铅笔芯制成电极并经实验证明它具有与玻碳电极类似的良好伏安特性。也曾用它作为基体电极，修饰８－羟基喹啉，研究了铜和锌的阳极溶出特性。本文研究了ｌ－（２－吡啶偶氮）－２－萘酚（ＰＡＮ）修饰的铅笔芯电极上铜的阳极溶出伏安特性，并用以测定了人发中的微量铜。探讨了铜在此电极上的预富集与溶出机理。２实验部分２．１仪器与试剂ＭＥＣ－１２Ａ型电化学分析仪，以ＰＡＮ修饰电极为工作电极，饱和甘汞电极为参比电极，铂电极为辅助电极，组成三电极体系。所有试剂均为分析纯试剂。水为二次去离子水。２．２电极…     

碳糊电极阳极吸附伏安法测定洛美沙星

报道了碳糊电极阳极吸附伏安法测定洛美沙星的新方法。在0.096mol L的KHP NaOH(pH5.4)缓冲液中,用碳糊电极为工作电极,在0.3V(vs.SCE)富集一定时间,然后从0.3～1 3V以300mV s扫速线性扫描,记录其在1 02V的二次导数阳极溶出峰。溶出峰电流与洛美沙星浓度在8.0×10-9～8.0×10-8mol L(富集90s)和8.0×10-8～8.0×10-7mol L(富集30s)范围内呈良好的线性关系,相关系数分别为0.9844和0.9967,检出限为9.0×10-10mol L(S N=3)。探讨了洛美沙星在碳糊电极上的伏安性质和电极反应机理,并且成功地应用于人体尿液中洛美沙星的测定,结果与紫外光度法基本吻合。     

芦荟大黄素在碳糊电极上的吸附催化伏安法研究

提出了一种以溶解氧为氧化剂，在碳糊电极（CPE）上吸附催化伏安法测定含蒽醌基药物的新方法。用线性扫描伏安法、循环伏安法和恒电位电解等手段研究了该催化伏安峰产生的机理。实验表明，芦荟大黄素能够有效地吸附富集在CPE表面上。在阴极化电位扫描过程中，芦荟大黄素被还原成蒽氢醌化合物，然后又立刻被溶液中的溶解氧氧化为芦荟大黄素，接着又在电极上被还原，从而形成一个催化循环。而在汞电极上芦荟大黄素产生一个可逆的氧化还原反应，观察不到其催化反应。在0.56 mol/L NH3-NH4Cl（pH8.9）缓冲溶液中，芦荟大黄素在CPE上于－0.60 V（ns.SCE）产生一灵敏的催化伏安峰。所述方法应用于中药大黄中的芦荟大黄素的测定，结果与高效液相色谱法基本一致。有机化合物在CPE和其它固体电极上的吸附催化伏安法灵敏度高,且电极无毒，显示出与汞电极不同的反应机理。它对于药物药理、药效、药物毒性、临床医学和生物化学有重要的意义。     

食用油粘合剂碳糊电极的制备及其应用

碳糊电极制作容易,应用电位范围广,重现性好。我们研制了植物油粘合剂碳糊电极,并用于药物等有机物的测定。硝基安定(Nitrazepam)是一种镇静剂,在欧洲广泛用作催眠剂,也可以用作外科手术的麻醉剂。它的分析方法有色谱法、分光光度法及极谱法。本文研究硝基安定在食用油粘合剂碳糊电极上的伏安特性。1　硝基安定的阴极溶出伏安曲线在pH3.00的乙酸乙酸钠缓冲溶液中,硝基安定在金龙鱼油甘油混合粘合剂碳糊电极上产生一阴极溶出伏安峰,峰电位在-1.15V左右,KCl影响峰电流和波形。硝基安定浓度在1.0×10-7～1.0×10-5molL范围内,峰高与浓度成良…     

碳糊电极测定甲硝唑的研究

报道了用碳糊电极测定甲硝唑的方法。在ｐＨ３．２的ＬｉＣｌ－ＨＣｌ电解溶液中，用二次导数阴极溶出伏安法测定甲硝唑。在碳糊电极上开路富集甲硝唑６０ｓ，然后记录其在－０．５８Ｖ的二次导数阴极溶出峰。溶出峰电流ｉｐ与甲硝唑浓度在３．０×１０－７～３．０×１０－６ｍｏｌ／Ｌ和３．０×１０－６～１．０×１０－４ｍｏｌ／Ｌ范围内呈良好的线性关系，相关系数分别为０．９９８６和０．９９９７，检出限为１．７×１０－７ｍｏｌ／Ｌ，相对标准偏差为６．０％（ｎ＝１０）。本方法直接用于甲硝唑片剂的测定，并用多种方法对甲硝唑在碳糊电极表面的反应机理进行了探讨。     

双向溶出伏安法同时检测金和铜

本文首次提出双向溶出伏安法 ,并将该方法用于同时检测水溶液中的Au(Ⅲ )和Cu(Ⅱ ) .采用细菌修饰的碳糊电极做工作电极 ,于阳极富集 ,阴极溶出测定Au(Ⅲ ) ,同时在碳糊电极上再修饰上一层超细微粒金膜 .然后 ,在金电极上进行阴极富集 ,阳极溶出检测Cu(Ⅱ ) .该法仪器设备简单、操作简便 .Au(Ⅲ )与Cu(Ⅱ )的检测信号分别在阴极、阳极两个方向显示 ,分辨率高 .Au(Ⅲ )在 0 .2～ 1μg/mL、Cu(Ⅱ )在 2～ 10ng/mL浓度范围内 ,均有良好线性关系 ,其检测限依次为 2 0ng/mL和 0 .5ng/mL ,8次平行测定RSD小于 3%     

金在脱乙酰壳多糖学修饰电极上的电化学行为及分析应用

用脱乙酰壳多糖化学修饰电极为工作电极，阳极溶出伏安法测定痕量金。在ｐＨ１￣２的ＫＣｌ－ＨＣｌ底液中，超始电位０．２０Ｖ，终止电位１．３０Ｖ，富集时间５ｍｉｎ，以－０．１／ｓ扫速阳极溶出，峰电位在１．００Ｖ（ｖｓ．ＳＣＥ），Ａｕ（Ⅲ）浓度在０．１０ｍｇ／Ｌ￣１０ｍｇ／Ｌ范围内与峰高呈线性关系。在富集１０ｍｉｎ时，可检测０．２５ｍｉｇ／ＬＡｕ，大大提高了测定灵敏度，用于矿样测定，无需分离，结果满意。用     

碳糊电极吸附／萃取伏安法测定氯氮平

本文提出了测定抗精神病新药氯氮平的碳糊电极开路富集/介质交换/溶出伏安法模式,该药物在0.45 V附近显示了氧化溶出峰,在1×10~(-6)～1×10~(-8)g/mL范围内峰电流与浓度成线性关系,检测限为4×10~(-9)g/mL,比紫外光度法提高约100倍。研究表明,碳糊电极对该药物具有强烈的萃取和吸附作用,并且萃取在富集过程中起着主要的作用。该法具有很强的抗干扰能力,可以直接测定片剂和尿样中的药物含量。     

Polybenzoin Based Sensor for Determination of 2thiouracil in Biological Fluids and Pharmaceutical Formulations

A carbon paste electrode was modified by electropolymerisation of benzoin using voltammetric technique. A novel polybenzoin modified carbon paste electrode (PB‐CPE) was developed for use as a detector in cyclic voltammetry and differential pulse adsorptive stripping voltammetry for the sensitive determination of 2thiouracil (2TU). The atomic force microscopy was applied to characterize the surface morphology of PB‐CPE. The modified electrode showed excellent electrocatalytic activity for the oxidation of 2TU. The oxidation process was irreversible over the pH range studied and exhibited a diffusion controlled behavior. All experimental parameters have been optimized. The peak current for the stripping of 2TU was found to be linear over the concentration range of 0.2–1.2 µM, with a detection limit of 2.21 nM. The practical application of the PB‐CPE in the determination of 2TU in human biological fluids and pharmaceutical samples were demonstrated that it has high sensitivity and good selectivity.     

Working Electrodes from Amalgam Paste for Electrochemical Measurements

Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA‐PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA‐PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA‐PE is high, and the electrode allows measurements at highly negative potentials. AgA‐PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2′‐bipyridine) can be performed on AgA‐PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes.     

A sensitive determination of dopamine in the presence of ascorbic acid using a nafion-coated clinoptilolite-modified carbon paste electrode

A selective dopamine determination using a nafion-coated clinoptilolite-modified carbon paste electrode in the presence of ascorbic acid was studied. Both cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) were used for measurements of dopamine. To improve the selectivity of the clinoptilolite-modified carbon paste electrode in presence of a high concentration of ascorbic acid, the electrode surface was coated with nafion membrane. Experimental parameters affecting the determination of dopamine, including the clinoptilolite ratio, nafion membrane thickness, preconcentration time, preconcentration solution pH, stripping solution pH and interferences are discussed. The developed sensor has a wide linear range, a low detection limit, and good stability and reproducibility. The sensor offers a good alternative to existing analytical methods for dopamine, permits a relatively short analysis time, and is simple, selective and inexpensive.     

Differential Pulse Adsorptive Stripping Voltammetric Determination of Chlorpyrifos at a Sepiolite Modified Carbon Paste Electrode

Abstract

An adsorptive stripping voltammetric (AdSV) method for the determination of organophosphorus insecticide chlorpyrifos at a bare carbon paste electrode (CPE) and clay modified carbon paste electrode (CMCPE) was developed. A systematic study of various experimental conditions, such as the pH, accumulation variables and composition of a modifier on the adsorptive stripping response, were examined by using differential pulse voltammetry. A significant improvement was observed in the sensitivity by using the present method with CMCPE. When CMCPE was used, a linear response was obtained over the concentration range 0.0001–2.0 ppm with lower detection limit of 0.00008 ppm, at an accumulation time of 80 s. The interference from other herbicides and ions on the stripping signal of the compound was also evaluated. The described method was applied to estimate the chlorpyrifos in environmental samples.     

L'electrode a Pate de Carbone Modifiee Son Utilisation en Voltammetrie par Redissolution Anodique a Impulsions Differentielles en Presence d'Un Film de Mercure

Abstract

The various problems which are associated with the use of carbon paste electrode as thin mercury film electrode (TKFE) for anodic stripping voltammetry (ASV) can be overcame in a very easy and rapid way. The procedure consists to coat the carbon paste surface by spraying a graphite based conductive solution. For example, the dispersion of colloidal graphite in a mixture of methyl polymethacrylate with butyl acetate (as solvent) gives interesting results. Such a surface is easily renewable and the electrode does not require any pretreatment procedure like cleaning or polarization cycles…, after coating. The technique offers the advantage to limit the risk of sample contamination and memory effects. After pulverisation, a hard, uniform and compact layer is formed after evaporation of the solvent excess.

The resulting electrode, electrochemically coated with mercury, exhibits a good stability as shown for the differential pulse anodic stripping voltammetry (DPASV) for cadmium ions. Replicate measurements were carried out in two different buffers at pH 8.5 and 5.0. Compared to the originally carbon paste electrode, a marked improvement of the reproducibility of the peak currents is observed. Calibration curves obtained by using the method of standard additions show a good linear relationship between cadmium ions concentration and peak current (down to 4×10^?10 M.L^?1).

After a deposition time of 10 minutes, the detection limit for cadmium is 1×10^?10 M.L^?l in both media).     

石墨烯/十二烷基硫酸钠复合物修饰碳糊电极测定氯霉素

以液体石蜡和硅油为混合粘合剂,与石墨粉混合制备了碳糊电极基底电极,将石墨烯/十二烷基硫酸钠复合物修饰在基底碳糊电极上,得到了基于石墨烯复合物的新型修饰碳糊电极。应用扫描电镜和循环伏安法分别研究了该电极的表面特性和电化学性质,结果表明,石墨烯和十二烷基硫酸钠修饰的碳糊电极增大了比表面积,有利于电子传递。在pH 3.0的HAc-NaAc缓冲溶液中,该修饰碳糊电极对氯霉素具有良好的电化学响应,氧化峰电位为0.194 V,氧化峰电流是基底碳糊电极的10倍。在最优实验条件下,该氧化峰电流与氯霉素的浓度在1.0×10~(-8)~5.0×10~(-4)mol/L范围内呈良好的线性关系,检出限为5.0×10~(-9)mol/L。该方法简便,重现性及选择性好,用于测定氯霉素滴眼液和虾中氯霉素残留,结果满意。     

电活化玻碳电极差分脉冲溶出伏安法测定磺胺嘧啶

采用线性循环溶出伏安法和差分脉冲溶出伏安法对磺胺嘧啶在电活化玻碳电极上的电化学行为进行了研究。玻碳电极在PBS溶液中(pH 7.0),用恒电位法在1.7 V阳极氧化400 s,在B-R缓冲溶液中,磺胺嘧啶在1.02V(vs.Ag/AgCl)处有一良好的氧化峰,在0.02～0.25 V/s范围内,其氧化峰电流与扫描速率呈良好线性关系,表明电极过程为受吸附控制的不可逆过程。差分脉冲溶出伏安法的氧化峰电流(Ipa)与磺胺嘧啶浓度1×10-6～1×10-4mol/L范围内呈良好的线性关系(r=0.9977),检出限为8.7×10-7mol/L(S/N=3)。方法已用于分析磺胺嘧啶片剂的分析。     

头孢氨苄在碳糊电极上的电化学行为及其分析研究

用循环伏安法和线性扫描伏安法研究了头孢氨苄在碳糊电极上的电化学行为,考察了不同电解质溶液、pH以及扫描速率等的影响。实验表明:在2.0 mol·L-1HCl支持电解质中,头孢氨苄的降解产物在-0.45 V(vs.SCE)处的电化学还原反应为2电子与2质子参加的受吸附控制的不可逆过程。还原峰电流与头孢氨苄的浓度的平方根在1.8×10-8～3.0×10-4mol·L-1范围内呈良好的线性关系,回收率在95.7%～101.5%范围,检出限(S/N=3)为1.0×10-8mol·L-1。并探讨了头孢氨苄在电极上的反应机理。     

Electrodeposition of mercury film on electrodes modified with clay minerals

A new type of carbon paste electrode modified with clay mineral and covered with a mercury film is presented in this work. Electrodeposition of the mercury film was performed on the carbon paste electrode modified with montmorillonite. The mercury film was deposited by both electrodeposition in situ and a preliminary electrodeposition. The pre-deposited film of mercury showed to be suitable for anodic stripping voltammetry. An open-circuit sorption of Cd, Pb, and Cu with subsequent anodic stripping voltammetry exhibited higher current responses of metals. Besides the enhanced sensitivity superior separation of the current responses during a simultaneous stripping of metals is expected to be achieved by means of the newly prepared electrode. Presented at the 57th Congress of Chemical Societies, Tatranské Matliare, 4–8 September 2005.     

Electrochemical determination of naproxen in the presence of acetaminophen using a carbon paste electrode modified with activated carbon nanoparticles

In this study, cyclic voltammetry and differential pulse voltammetry were used to determine the electrochemical properties and concentration of naproxen in pharmaceutical formulation and human serum samples by using a carbon paste electrode modified with activated carbon nanoparticles. Optimum conditions were obtained at an electrode with 0.005 g activated carbon nanoparticles in a phosphate buffer solution of pH 6 as a supporting electrolyte. Linear calibration curves were obtained in the range of 0.1–120 μM, and the detection limit of naproxen determined was 0.0234 μM. The modified electrode shows good selectivity for naproxen in the presence of some organic and inorganic interferences and very good precision in real samples. Finally, naproxen was measured in the presence of acetaminophen.