Iodide‐Selective Electrode Based on Copper Phthalocyanine

Copper phthalocyanine was used as ion carrier for preparing polymeric membrane selective sensor for detection of iodide. The electrode was prepared by incorporating the ionophore into plasticized poly(vinyl chloride) (PVC) membrane, coated on the surface of graphite electrode. This novel electrode shows high selectivity for iodide with respect to many common inorganic and organic anions. The effects of membrane composition, pH and the influence of lipophilic cationic and anionic additives and also nature of plasticizer on the response characteristics of the electrode were investigated. A calibration plot with near‐Nernestian slope for iodide was observed over a wide linear range of five decades of concentration (5×10^?6?1×10^?1 M). The electrode has a fast response time, and micro‐molar detection limit (ca. 1×10^?6 M iodide) and could be used over a wide pH range of 3.0–8.0. Application of the electrode to the potentiometric titration of iodide ion with silver nitrate is reported. This sensor is used for determination of the minute amounts of iodide in lake water samples.     

PVC膜修饰电极上零电流示波电位滴定法测定硼的研究

以氯化十六烷基吡啶（ＣＰＣ）和氟硼酸钠形成的离子缔合物为活性物质，制成ＰＶＣ膜涂层石墨电极，提出了一个快速测定硼的零电流示波电位滴定法。以ＣＰＣ为滴定剂，用ＰＶＣ膜电极为指示电极，甘汞电极为参比电极，利用阴极射线示波器荧光屏上荧光点的突然位移来指示ＣＰＣ滴定硼的终点，具有灵敏、准确、快速等特点，用该法测定玻璃中的硼，结果良好。     

Novel Potentiometric PVC‐Membrane and Coated Graphite Sensors for Lanthanum(III)

Preliminary theoretical studies revealed the selective complexation of bis (2‐mercaptoanil) diacetyl (BMDA) with La³⁺ over several alkali, alkaline earth and heavy metal ions. Thus, novel PVC‐based membrane (PBM) and coated graphite membrane (CGM) sensors for La(III) based on BMDA were prepared. The electrodes display Nernstian behavior over wide concentration ranges (i.e., 1.0×10^?5–1.0×10^?1 M for PBM and 1.0×10^?6–1.0×10^?1 M for CGM). The potential response of sensors was pH independent in the range of 4.0–8.0. The sensors possess satisfactory reproducibility, fast response time (<15 s), and specially excellent discriminating ability for La³⁺ ions with respect to most of the cations. The membrane sensor was used as an indicator electrode in potentiometric titration of lanthanum ions with EDTA. The coated graphite membrane electrode was applied in determination of fluoride ions in mouth wash preparations.     

1,3,4-Trisubstituted-2-azetidinone Derivatives as Novel Receptors for Bismuth(III) Ion-Selective Electrodes: Application in Pharmaceutical and Glass Samples

Abstract

Polymeric membrane electrodes (PMEs) and coated graphite electrodes (CGEs) containing 1,3,4-trisubstituted-2-azetidinone derivatives as ion carriers are reported here for bismuth(III) ion selectivity. These electrodes exhibited Nernstian response for Bi³⁺ ions over a wide concentration range (5.0 × 10^?7 M to 1.0 × 10^?1 M for CGE) with a lower detection limit of 3.98 × 10^?7 M (for CGE) and wide pH range (1.3–5.0). Compared to polymeric membrane electrode, the coated graphite electrode has shown better selectivity for Bi³⁺ ions with respect to common metal ions. Proposed electrodes have been used for the estimation of Bi³⁺ ions in pharmaceutical and glass samples.     

Uranyl-selective PVC membrane electrodes based on some recently synthesized benzo-substituted macrocyclic diamides

Four different recently synthesized macrocyclic diamides were studied to characterize their abilities as uranyl ion carriers in PVC membrane electrodes. The electrodes based on macrocycle 1,18-diaza-3,4;15,16-dibenzo-5,8,11,14,21,24-hexaoxacyclohexaeicosane-2,17-dione resulted in a Nernstian response for UO(2)(2+) ion over wide concentration ranges. The linear concentration range for the polymeric membrane electrode (PME) is 3.0x10(-6)-8.2x10(-3) M with a detection limit of 2.2x10(-6) and that for the coated graphite electrode (CGE) is 5.0x10(-7)-1.5x10(-3) M with a detection limit of 3.5x10(-7) M. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations.     

New Ion‐Pair Based All‐Solid‐State Surfactant Sensitive Sensor for Potentiometric Determination of Cationic Surfactants

Cationic surfactants of different types were determined using a few potentiometric sensors based on ion‐pair complexes (dodecyldimethylbenzylammonium dodecylsulfate, dodecylmethylbenzylammonium dodecylbenzensulfonate, tetrahexadecylammonium dodecylsulfate and Hyamine (benzethonium dodecylsulfate)) as sensing materials. The response of the all‐solid state surfactant sensitive electrode based on a Teflonized graphite conducting substrate, coated with a PVC membrane containing sensing material, was investigated in the solutions of Hyamine and hexadecyltrimethylammonium ion in the concentration range from 1 μM to 10 mM. Potentiometric surfactant cation titration has been performed using sodium dodecylsulfate as titrant and an ion‐pair‐based surfactant sensitive electrode as a potentiometric indicator. Several commercial surfactant products have also been titrated and the results were compared with those obtained with two‐phase standard titration method.     

Determination of SCN- in urine and saliva of smokers and non-smokers by SCN(-)-selective polymeric membrane containing a nickel(II)-azamacrocycle complex coated on a graphite electrode.

The construction, performance characteristics, and application of a novel polymeric membrane coated on a graphite electrode with unique selectivity towards SCN- are reported. The electrode was prepared by incorporating Ni(II)-2,2,4,9,9,11-hexamethyltetraazacyclotetradecanediene perchlorate into a plasticized poly(vinyl chloride) membrane. The influences of membrane composition, pH and foreign ions were investigated. The electrode displays a near Nernstian slope (-57.8 mV decade-1) over a wide concentration range of 1 x 10(-7)-1 x 10(-1) M of SCN- ion. The electrode has a detection limit of 4.8 x 10(-8) M (2.8 ng/cm3) SCN- and shows response times of about 15 s and 120 s for low to high and high to low concentration sequences, respectively. The proposed sensor shows high selectivity towards SCN- over several common organic and inorganic anions. The electrode revealed a great enhancement in selectivity coefficients and detection limit for SCN-, in comparison with the previously reported electrodes. It was successfully applied to the direct determination of SCN- in milk and biological samples, and as an indicator electrode in titration of Ag+ ions with thiocyanate.     

对电极材料对非贵金属电催化剂耐久性评价的影响

质子交换膜燃料电池(PEMFCs)环境友好,具有高的能量转换效率,已受到了广泛的关注.目前,铂基电催化剂广泛使用在 PEMFCs中,但铂的储量有限,活性低,耐久性差,成本高,急需开发高性能的非贵金属电催化剂替代铂基电催化剂.非贵金属电催化剂的电化学表征基本上都沿用了铂基电催化剂的评价体系和方法,不一定适用于非贵金属电催化剂的表征.
　　本文选用铂和石墨为对电极考察其对非贵金属电催化剂在酸性电解质中耐久性测试的影响.当使用铂对电极时,商业 Pt/C电催化剂的氧还原(ORR)活性随着耐久性测试圈数的增加而降低,而非贵金属电催化剂的氧还原活性在耐久性测试过程中的变化规律与商业 Pt/C不同,呈现先降低,后升高的规律.耐久性测试前后的透射电镜(TEM)分析表明非贵金属电催化剂经过耐久性测试后,在电催化剂表面生长了铂纳米颗粒.高分辨透射电镜(HRTEM)和能量色散 X射线光谱(EDX)进一步证明以铂为对电极的三电极体系,在进行非贵金属电催化剂耐久性测试的过程中,非贵金属电催化剂表面生长了铂纳米颗粒,使得非贵金属电催化剂的 ORR活性在耐久性测试后得到显著提高.耐久性测试前后,非贵金属电催化剂氧还原过程的电子转移数由3.7变为4.0,再次证明了耐久性测试过程中铂颗粒的生成.在三电极电化学体系中,当工作电极发生阴极反应时,对电极为阳极反应,反之亦然,即在工作电极上发生的任何电化学过程,都会在对电极上完成相反的电化学过程.在循环电位扫描过程中,当铂对电极的电压高于1.0 V (vs RHE)时,开始发生铂的溶解现象,并且当电压高于1.2 V (vs RHE)时,铂的溶解量会急剧增加,部分溶解的铂会扩散到工作电极附近,并在工作电极的非贵金属电催化剂表面发生沉积作用.随着扫描圈数的增加,沉积的铂纳米颗粒的数量增加,颗粒变大,从而使非贵金属电催化剂的表观 ORR活性显著提高.该现象使得非贵金属电催化剂在酸性电解质中无法表现出其真实的耐久性.当选用石墨棒为对电极材料时,非贵金属电催化剂在酸性电解质中的 ORR活性不会受到对电极材料的影响.
　　通过考察对电极材料对非贵金属电催化剂在酸性电解质中耐久性能的影响,可以得出结论,即对非贵金属电催化剂在酸性电解质中的耐久性测试中,不宜使用铂对电极,应该使用石墨为对电极材料,以防止对电极材料干扰耐久性测试.     

Optimization of polymeric triiodide membrane electrode based on clozapine-triiodide ion-pair using experimental design

Central composite design (CCD) and response surface methodology (RSM) were developed as experimental strategies for modeling and optimization of the influence of some variables on the performance of a new PVC membrane triiodide ion-selective electrode. This triiodide sensor is based on triiodide-clozapine ion-pair complexation. PVC, plasticizers, ion-pair amounts and pH were investigated as four variables to build a model to achieve the best Nernstian slope (59.9 mV) as response. The electrode is prepared by incorporating the ion-exchanger in PVC matrix plasticized with 2-nitrophenyl octal ether, which is directly coated on the surface of a graphite electrode. The influence of foreign ions on the electrode performance was also investigated. The optimized membranes demonstrate Nernstian response for triiodide ions over a wide linear range from 5.0 x 10(-6) to 1.0 x 10(-2)mol L(-1) with a limit of detection 2.0 x 10(-6) mol L(-1) at 25 degrees C. The electrodes could be used over a wide pH range 4-8, and have the advantages of easy to prepare, good selectivity and fast response time, long lifetime (over 3 months) and small interferences from hydrogen ion. The proposed electrode was successfully used as indicator electrode in potentiometric titration of triiodide ions and ascorbic acid.     

Molecularly imprinted polymer Based PVC-Membrane-Coated graphite electrode for the determination of metoprolol

A PVC-based membrane containing metoprolol molecularly imprinted polymer (MIP) coated directly on graphite electrode for the determination of metoprolol in real samples is reported. This potentiometric sensor was designed by dispersing the MIP particles in dioctylphthalate plasticizer as solvent mediator and then embedded in polyvinyl chloride matrix. The electrode exhibited a near-Nernstian slope of 55.4 ± 1 mV decade^-1 for metoprolol over a wide concentration range between 2.0 × 10^-7-8.0 × 10^-3 M and a detection limit of 1.3 × 10^-7 M. With a response time of about 14 s it could be used for at least 6 months without any divergence in potential. The proposed electrode can be used in the pH range of 3.5-10.5 and can reveal good selectivities for metoprolol over a wide variety of ions. Finally, the designed sensor was successfully applied as an indicator electrode to determine the concentration of metoprolol in tablets, human urine and plasma. The results were compared favorably with those obtained by HPLC method and showed satisfactory agreements with them.     

A new construction for a potentiometric, enantioselective membrane electrode--its utilization to the S-captopril assay

A novel potentiometric, enantioselective membrane electrode based on graphite paste (graphite powder and paraffin oil) has been constructed. The graphite paste is impregnated with 2-hydroxy-3-trimethylammoniopropyl-beta-cyclodextrin (as chloride salt) solution, 10(-3) mol l(-1). The potentiometric, enantioselective membrane electrode can be used reliable for S-captopril assay as raw material and from Novocaptopril tablets, using a chronopotentiometry (zero current) technique, in the 10(-6)-10(-2) mol l(-1) concentration range (detection limit 2 x 10(-7) mol l(-1)), with an average recovery of 99.99% (RSD=0.05%). The enantioselectivity was determined over R-captopril and D-proline. The response characteristics of the enantioselective, potentiometric membrane electrode were determined also for R-captopril. It was shown that only L-proline is the main interfering compound. The surface of the electrode can be regenerated by simply polishing, obtaining fresh surface ready to be used in a new assay.     

PVC-based Cu (II)-Schiff base complex membrane coated graphite electrode for the determination of the triiodide ion

A triiodide-selective electrode based on copper (II)-Schiff base complex as a membrane carrier is proposed. The electrode was prepared by incorporating the carrier into a plasticized polyvinylchloride (PVC) membrane and was directly coated on the surface of a graphite electrode. The obtained electrode showed a near Nernstian slope of 57.0 ± 0.4 mV/decade to I ₃ ⁻ ions over an activity range of 1.0 × 10⁻⁵−1.0 × 10⁻¹ M with a limit of detection of 4.8 × 10⁻⁶ M. The response time of the electrode was fast (5 s) and the electrode could be used for about 2 months without considerable divergence in response. The potentiometric selectivity coefficients were evaluated and displayed anti-Hofmeister behavior. The electrode was used as an indicator electrode in the potentiometric titration of the triiodide ion and in the determination of ascorbic acid in vitamin C tablets. The text was submitted by the authors in English.     

Electrocatalytic reduction of oxygen at electrodes coated with a bimetallic cobalt(II)/platinum(II) porphyrin

Edge plane pyrolytic graphite (EPG) electrodes coated with 5-(4-pyridyl)-10,15,20-tris(3-methoxy-4-hydroxyphenyl)porphyrin and its Pt(II) and Co(II)/Pt(II) analogs undergo an electrochemical-chemical-electrochemical (ECE) reaction when anodically scanned in 1.0 M HClO4. The new redox couple formed from this anodic conditioning of the coated electrode is dependent on the pH of the solution. Roughened EPG electrodes coated with the Co(II)/Pt(II) bimetallic porphyrin show a catalytic shift of 500 mV for the reduction of O2 when compared to the reduction of O2 at a bare EPG electrode. An additional catalytic shift of ca. 100 mV is observed for O2 reduction at an EPG electrode coated with the Co(II)/Pt(II) porphyrin which has been oxidized in 1.0 M HClO4. In addition to the added electrocatalysis a significant percentage of O2 reduced at the oxidized Co(II)/Pt(II) EPG electrode is converted to H2O as determined by rotating disk electrode measurements.     

盐酸黄连素示波电位滴定法的研究

黄连素(小檗碱)是一种重要的抗菌素药,用于治疗细菌性痢疾和一般炎症。现行的分析方法为碘量法,比较烦琐。本文将示波电位滴定法中的金属片电极涂上一层含活性物质的PVC膜,使电极对黄连素等有机药物产生一定的响应,可用于四苯硼酸钠直接滴定黄连素的终点指示。该方法比药典法、直接电位法更简便、直观,易推广使用,同时也扩大了示波电位滴定法的应用范围。     

Ni-P-C复合材料的制备及其电催化产氢性能研究

通过化学镀技术制备了亚微米级的Ni-P镀层石墨粉复合粉体新材料(即Ni-PC).采用扫描电子显微镜、X-射线能谱仪、X-射线粉末衍射仪对Ni-P-C复合粉体分别进行表面形貌分析、表面成分分析和物相分析.通过对Ni-P-C材料电极进行电解水析氢、循环伏安和Tafel极化等电化学测试,研究对比了Ni-P-C(石墨)材料与试剂石墨粉体以及纯Ni电极的电化学催化产氢性能.结果表明:利用化学镀技术成功地在石墨粉体表面镀上了一层亚微米级且均匀、致密的非晶态Ni-P合金.Ni-P-C(石墨)复合电极材料析氢能力强,具有良好的电化学活性.     

A novel wire-type lead-selective electrode based on bis (1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine

The preparation of a lead-selective electrode based on bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) as sensing material is reported. The plasticized PVC membrane containing 30% PVC, 67% ortho-nitrophenyloctylether (NPOE) and 3% ionophore L was directly coated on a graphite rod. This electrode exhibits a nearly Nernstian slope of 27.8+/-0.2 mV decade(-1) over a concentration range 10(-6)-10(-2) M with a detection limit of 4.0 x 10(-7) M. The response time of the electrode was found to be <20 s. The potential of the sensor was independent on pH variations in the range 5-7. The selectivity of the electrode towards lead ions over Na+, K+, Ag+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, La3+, Sm3+ and Er3+ ions was investigated. The prepared electrode was successfully used as an indicator for titration of a lead solution with a standard solution of EDTA. The applicability of the sensor for Pb2+ measurement in various synthetic and real samples has been also demonstrated.     

A Novel PVC‐Membrane‐Coated Graphite Sensor Based on an Anthraquinone Derivative Membrane for the Determination of Lead

A highly selective membrane electrode for the determination of ultratrace amounts of lead was prepared. The PVC membrane electrode based on 2‐(2‐ethanoloxymethyl)‐1‐hydroxy‐9,10‐anthraquinone (AQ), directly coated on graphite, exhibits a good Nernstian response for Pb(II) ions over a very wide concentration range (1.0×10^?7–1.0×10^?2 M) with a limit of detection of 8.0×10^?8 M. It has a fast response time of ca. 10 s and can be used over a period 2 months with good reproducibility (SD=±0.2 mV). The electrode revealed a very good selectivity respect to common alkali, alkaline earth, transition and heavy metal ions and could be used in the pH range of 3.5–6.8. It was used as an indicator electrode in potentiometric titration of lead ions with chromate and oxalate, and in indirect determination of lead in spring water samples.     

A comparative study of chromium(III) ion-selective electrodes based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III)

A comparative study was made between three types of Cr(III) ion-selective electrodes: PVC membrane electrode, silver coated electrode and modified carbon paste electrode based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III) complex (Crsalophen). As anticipated, electrodes with a solid contact, rather than a traditional liquid inner contact, give lower detection limits because of diminished ion fluxes. Often, however, ill-defined solid contact gives rise to instabilities and interferences by oxygen gas. The carbon paste electrode provides a more sensitive and stable device than that afforded by PVC and coated electrodes. The best performance was obtained by an electrode based on the paste containing 3.5 wt% Cr-complex, 48.5% graphite plasticized with a mixture of 24.0 wt% tris(2-ethylhexyl) phosphate (DOPh) + 24.0 wt% dioctyl sebacate (DOS). The sensor has a linear dynamic range of 7.5 × 10^-6 to 1.0 × 10^-2 M, with a Nernstian slope of 20.1 ± 0.6 mV decade^-1, and a detection limit of 1.8 × 10^-6. It has a short response time of a bout 8 s and is applicable in a pH range of 4.5-7.7. It was successfully used as an indicator electrode in potentiometric titration of Cr(III) with EDTA and in determination of Cr(III) in water samples and chromium in (Crsalophen).     

Mg0.9Ti0.1Ni0.85Co0.15合金的石墨粉及镍粉球磨表面包覆性能

选用非晶态的Mg0.9Ti0.1Ni0.85Co0.15合金粉末与石墨粉及镍粉进行球磨表面包覆。SEM分析结果表明,己包覆石墨和镍粉的合金表面上吸附着一层小的颗粒,形成薄层将原来的合金表面包覆起来。使用XPS分析了合金表面元素。结果表明,包覆石墨粉后,合金表面碳元素的质量分数和原子分数均增加,Mg的质量分数从22.74%减小至22.23%,原子分数从36.43%减小到32.94%,从而减小了Mg在碱液中的腐蚀几率,提高合金的抗腐蚀性能;包覆镍粉后,合金表面Ni的质量分数由59.89%增加到60.04%,原子分数由40.63%增加到41.02%,形成合金表面富Ni的保护层,提高了合金的抗腐蚀性能。充放电循环测试表明,循环30周后,包覆石墨粉的合金电极容量保持率为32.05%,包覆镍粉的合金电极容量保持率为41.26%,而未包覆的电极容量保持率仅为17.88%。合金电极极化曲线测试结果表明,石墨或镍粉的包覆提高了Mg0.9Ti0.1Ni0.85Co0.15合金电极的循环稳定性和在KOH碱液中的抗腐蚀性能。     

Novel Electrochemical Sensor for Sunset Yellow Based on a Platinum Wire–Coated Electrode

Abstract

In this research, the construction and general performance characteristics of a sunset yellow sensor based on sunset yellow–cetyl pyridinum (SY-CPY) ion pair as an ion exchanger were described. A coated platinum wire electrode (CPE) was prepared and compared with coated graphite (CGE) and membrane electrode (PME). The CPE exhibited a rapid and Nernstian response (?29.77 ± 0.2 mV decade^?1) to SY concentration range from 3.16 × 10^?7 to 3.16 × 10^?3 mol dm^?3 within pH 4.5–9.5. Interfering effects of some foreign substances were reported. The optimized matrix was successfully applied to the determination of SY in artificial mixtures and commercial soft drinks. The results showed good agreements with the determination made by use of high-performance liquid chromatography.