A Membrane Sensor for Selective Determination of Bisacodyl in Tablets

A novel PVC membrane sensor for bisacodyl based on bisacodyl‐phosphotungstate ion pair complex was prepared. The influence of membrane composition (i.e. percent of PVC, plasticizer, and ion‐pair complex), pH of test solution and foreign cations on the electrode performance were investigated. The optimized membrane demonstrates Nernstian response (60.3 ± 2.1 mV per decade) for bisacodyl cations over a wide linear range from 8.0 × 10^?5 to 5.0 × 10^?3 M at 25 °C. The potentiometric response is independent from the pH of the solution in the pH range of 1.5–3.5. The proposed sensor has the advantages of easy preparation, good selectivity, fast response time, and small interferences from hydrogen ions. It was successfully used for determination of bisacodyl in tablets, and the results obtained with the electrode were in good agreement with the official chromatographic method.     

Novel monohydrogenphosphate sensor based on vanadyl salophen

A novel PVC-based membrane sensor based on vanadyl salophen (VNSP) for determination of trace amounts of monohydrogenphosphate (MHP) ions is introduced. The electrode revealed Nernstian response towards monohydrogenphosphate over the wide concentration range from 1.0×10⁻¹ to 1.0×10⁻⁶ M at the pH of 8.2. The effect of solvent mediator, cationic additives and amount of ion-carrier on the behavior of the sensor was investigated. The sensor shows a short response time (<20 s) in the whole concentration ranges. The selectivity of the electrode is very high, and it can be used for detection of trace amounts of monohydrogenphosphate in the presence of large amounts of other anions. The detection limit of the electrode was 5.0×10⁻⁷ M (48 ng/ml) and it could be used for 14 weeks without any measurable changes in the slope. The potentiometric selectivity coefficients data revealed negligible interference from 16 common anions. It was successfully applied for the direct determination of monohydrogenphosphate in fertilizer samples and, as an indicator electrode, in potentiometric titration of HPO₄²⁻ ion with barium nitrate.     

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in polymeric membrane type ion‐selective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such membrane electrodes display undesirable super‐Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super‐Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized membranes formulated with Al(III)‐PFP in an o‐nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 μM, with very high selectivity over SCN^?, ClO₄^?, Cl^?, Br^? and NO₃^? (k^pot<10^?3 for all anions tested). With further refinements in the membrane chemistry, it is anticipated that Al(III) porphyrin‐based membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid‐state LaF₃ crystal‐based fluoride sensor.     

A Novel Modified Carbon Paste Electrode for Potentiometric Determination of Mercury(II) Ion

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand of Ethyl‐2‐(benzoylamino)‐3‐(2‐hydroxy‐4‐methoxyphenyl)‐2‐propenoate (EBHMP) as a suitable carrier for Hg²⁺ ion was described. The electrode exhibit a super Nernstian slope of 48.5±1.0 mV per decade for Hg²⁺ ion over a wide concentration range from 3.0×10^?7–3.1×10^?2 M. The lower detection limits are 1.0×10^?7 M Hg²⁺. The electrode has a fast response time (ca. 5 s), a satisfactory reproducibility and relatively long life time. The proposed sensor shows a fairly good selectivity toward Hg²⁺ ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 1.0–4.0. The proposed electrode was used as an indicator electrode in potentiometric titration of mercuric ion with standard solution of EDTA. The direct determination of mercury in spiked wastewater and an amalgam sample gave results that compare favorably with those obtained by the cold vapor atomic absorption spectrometric method.     

Solid Contact Nitrate Ion‐Selective Electrode Based on Ionic Liquid with Stable and Reproducible Potential

A simple, fast and cheap method of preparation of solid contact nitrate ion‐selective electrode is proposed. The electrode membrane phase consist of only three components: PVC, plasticizer and ionic liquid (IL).The ionic liquid trihexyltetradecylphosphonium chloride is used in triple function as ionophore, as lipophilic ionic component in order to reduce membrane resistance, and as transducer media in order to stabilize the potential of internal Ag/AgCl electrode. The electrical properties of the membrane were studied by electrochemical impedance spectroscopy and the influence of the interfacial water film was evaluated by potentiometric water layer test.     

Ketoconazol‐Triiodide Ion Pair Complex as a Suitable Carrier in an Iodide Selective Membrane Electrode

A novel membrane sensor for selective monitoring of iodide, consisting of a triiodide‐ketoconazole ion pair complex dispersed in a PVC matrix, plasticized with a mixture of 2‐nitrophenyl octyl ether and dioctylphtalate with unique selectivity toward iodide ions, is described. The influence of membrane composition, pH of test solution and foreign ions on the electrode performance were investigated. The optimized membrane demonstrates a near‐Nernstian response for iodide ions over a wide linear range from 1.0 × 10^?2 to 1.0 × 10^?5 M, at 25 ± 1 °C. The electrode could be used over a wide pH range 3–10 and has the advantages of high selectivity, fast response time and good lifetime (over 4 months). It was successfully used as indicator electrode in potentiometric titrations and direct potentiometric assay of iodide ions.     

聚氯乙烯膜盐酸地尔硫卓离子选择电极测定盐酸地尔硫卓

制备了一种以盐酸地尔硫卓与碘汞酸盐形成的缔合物为电活性物质的聚氯乙烯膜盐酸地尔硫卓选择电极,并对其性能做了测定,结果显示该电极对盐酸地尔硫卓有较好的能斯特响应。盐酸地尔硫卓的线性范围为4.5×10~(-2)～1.0×10~(-4)mol·L~(-1),检出限为3.55×10~(-5)mol·L~(-1)。该电极用于盐酸地尔硫卓片剂的分析,结果与药典法结果相符。     

Electroanalytical Studies on Cobalt(II) Ion‐Selective Sensor of Polymeric Membrane Electrode and Coated Graphite Electrode Based on N2O2 Salen Ligands

Poly(vinyl chloride)‐based membranes of salen ligands, 2‐((E)‐((1R,2S)‐2‐((E)‐5‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4‐tert‐butyl phenol (S₁) and 2‐((E)‐((1R,2S)‐2‐((E)‐3,5‐di‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4,6‐di‐tert‐butylphenol (S₂) were fabricated and explored as cobalt(II) selective electrodes. The performance of the polymeric membrane electrode (PME) and coated graphite electrode (CGE) were compared and it was observed that CGE showed a wide working concentration range of 1.1×10^?8 to 1.0×10^?1 mol L^?1 with a limit of detection of 7.0×10^?9 mol L^?1 exhibiting the Nernstian slope 29.6 mV/decade of activity in the pH range 3.0–9.0. It was used for the determination of cobalt(II) ions in water, soil, beer, pharmaceutical samples and medicinal plants and would be used as an indicator electrode in potentiometric titration with EDTA.     

新型涂碳式双嘧达莫选择电极的研制与应用

报道了一种以双嘧达莫与碘化铋形成的缔合物为电活性物的新型涂碳式PVC膜双嘧达莫选择电极,测定了双嘧达莫片的含量。电极线性响应范围为1.0×10-2~2.2×10-5mol/L,级差电位为48 mV/pc,检出限为1.8×10-5mol/L。该电极响应迅速,重现性好,分析结果与药典法相符。     

离子选择性电极电位法测定钼矿石和钨矿石中氟

采用过氧化钠熔融钼矿石、钨矿石样品,乙二胺四乙酸钠和5-磺基水杨酸混合溶液浸取盐分,将样品溶液静置12h,吸取上层清液,以乙二胺四乙酸钠-硝酸钾组成的混合溶液作为总离子强度缓冲剂,控制溶液pH值为5.1,使用pF-1型氟离子选择电极,以饱和甘汞电极作参比电极测定溶液的平衡电位值。采用标准曲线法测定钼矿石和钨矿石中氟。钼矿石标准物质测定值的相对标准偏差(n=11)为3.36%,经4种国家一级钼矿石、钨矿石标准物质的分析验证,测定结果与标准值吻合。     

Novel Copper(II)‐Selective Membrane Electrode Based on a New Synthesized Schiff Base

A PVC membrane electrode for copper(II) ion based on a recently synthesized Schiff base as a suitable ion carrier was constructed. The electrode exhibits a Nernstian slope of 28.3 ± 0.6 mV per decade of Cu²⁺ over a wide concentration range of 7.0 × 10^?6‐2.6 × 10^?2 M with a detection limit of 5.0 × 10^?6M in the pH range of 4.2–5.8. The response time is about 10s and it can be used for at least 1 month without any considerable divergence in potential. It was successfully applied as an indicator electrode in the potentiometric titration of copper ions.     

Determination of Chlorides in Meat Products with Ion‐Selective Electrode Using the Batch Injection Technique

A procedure was developed for determination of salt in various meat products using a chloride ion‐selective electrode. The technique of batch injection analysis was used together with an ultrasound based sample extraction step. Various kinds of meat products were analyzed. The relative standard derivation lies between 0.9% and 2.7%. The accuracy of the method was proved by an independent reference method. Differences between the results of the batch injection analysis method and the reference method were found to be statistically non‐significant. Total analysis time was 7 minutes on average. The described batch injection analysis method is fast, accurate, reliable and suitable for routine analytical work.     

A Novel Ion‐Selective Electrode for Determination of the Mercury(II) Ion Based on Schiff Base as a Carrier

A new poly(vinyl chloride) (PVC) membrane ion‐selective electrode based on bis‐salicyladehyde‐diaminjodipropylamine (BSDDA) as an ion carrier was successfully applied to the detection of Hg²⁺ ions. This electrode displayed good selectivity toward Hg²⁺ in comparison with other metal ions and exhibited a Nernstian slope of 30.5 ± 0.4 mV per decade of Hg²⁺ over a concentration range of 9.5 × 10^?7 to 6.4 × 10^?2 M of Hg²⁺ in the pH range 1.5 to 3.5. The detection limit was 7.0 ± 0.2 × 10^?7 M and response time was about 10 s to 25 s. The electrode can be used at least 2 months without apparent divergence in potential. In addition, the effects of experimental parameters such as membrane composition, nature and amounts of plasticizer and additive were investigated. The proposed electrode could be used as an indicator electrode in the detection of Hg²⁺ in samples.     

Chemically Modified Carbon Paste Electrode for Determination of Sulfate Ion by Potentiometric Method

Four Schiff base complexes of different metal ions, M=Cr(III), Mn(III), Fe(III), and Co(III), were studied to characterize their ability as sulfate ion carriers in carbon paste electrode (CPE). The modified CPE electrode with Schiff base complex of Cr(III), N,N′‐ethylenebis(5‐hydroxysalicylideneiminato) chromium(III) Chloride, showed good response characteristics to SO₄^2? ion. The proposed electrode exhibits a Nernstian slope of 28.9±0.4 mV per decade for SO₄^2? ion over a wide concentration range from 1.5×10^?6?4.8×10^?2 M, with a detection limit of 9.0×10^?7 M. The CPE electrode manifested advantages of relatively fast response time, suitable reproducibility and life time and, most important, good potentiometric selectivity relative to a wide variety of other common inorganic anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 4.0–9.0. The proposed electrode was used as an indicator electrode in potentiometric titration of sulfate with Ba²⁺ ion, the determination of zinc in zinc sulfate tablet and also determination of sulfate content of a mineral water sample.     

离子选择性电极法测定药剂中的头孢氨苄

基于头孢氨苄在０．１０ｍｏｌ／Ｌ ＮａＯＨ介质中,沸水浴降解２００ｍｉｎ后,能生成硫醇化合物,利用硫离子选择电极研究了测定头孢氨苄条件,其浓度在６．０×１０＾－５￣１×１０＾－２ｍｏｌ／Ｌ范围,电位Ｅ与浓度对数呈线性关系,并将此方法用于胶囊中头孢氨苄的测定,回收率为１０４．０％。     

Selective Determination of Nicorandil with a Single Planar Solid-state Potentiometric Ion Selective Electrode

Novel screen-printed electrodes (SPEs) were constructed for the quantitation of nicorandil (NIC) in its pharmaceutical formulations. Different ion-exchangers and plasticizers were investigated, but the optimal potentiometric response was obtained using nicorandil-phosphotungstate (NIC-PTA) ion associate and tricresyl phosphate as a plasticizer. A Nernstian response of 58.80±1 mV/decade was obtained over a concentration range of (1×10⁻⁶–1×10⁻²) M with 1×10⁻⁵ M as a detection limit. Sensor morphology was characterized using scanning electron microscopy (SEM). The method was validated for the assay of NIC with high selectivity, accuracy (average recovery=100.54 %), and precision (%RSD≤2).     

长寿命高选择性液膜碘离子电极的研究

合成了PVC-双硫腙-Hg(Ⅱ)载体.以该载体物质制备了高选择性碘离子电极,其选择性次序为:I^-》ClO₄^->SCN^->NO₂^-》Sal^-～Br^->NO₃^->Cl^-.电极对碘离子的线性响应范围为1×10^-3～5×10^-7mol/L,检测下限为2×10^-7mol/L,斜率为(59±1)mV/decade(16℃).并研究了电极的响应机理,表明系碘离子与载体中金属汞原子直接作用.将该电极应用于食盐中碘的测定,取得了满意的结果.     

Preparation of Iodide Selective Carbon Paste Electrode with Modified Carbon Nanotubes by Potentiometric Method and Effect of CuS‐NPs on Its Response

In this research, multiwalled carbon nanotubes (MWCNTs) was oxidized and chemically modified through reaction with 3‐(trimethoxysilyl)propan‐1‐amine (TMSPA) and their subsequent reaction with 2‐hydroxy‐3‐methoxy benzaldehyde. Subsequently, this material was metalized by reaction with copper acetate that lead to formation and impergeation of 2‐methoxy‐6‐((3‐(trimethoxysilyl)propylimino)methyl)phenol MMSPIMP? MWCNT‐Cu. This novel material was identified with different techniques such as SEM and FT‐IR analysis. In this work, the reported material are exhibited high accurate and repeatable monitoring of iodide due to its high surface area with various reactive centre. It exhibited selectivity for iodide over the wide linear dynamic range between 1.8×10^?6 and 1.15×10^?1 M, with a Nernstian slope of ?59.12±0.7 mV per decade of activity and detection limit of 1.8×10^?6 M. Copper sulfide nanoparticles were prepared and their effect on the electrode response was investigated. The results were improved in the presence of nanoparticles with fast and stable response, good reproducibility, long‐term stability, high selectivity over the presence of common organic and inorganic anions, high detection limit and dynamic range. The proposed sensor has been applied as potentiometric determination of some iodine species over a pH range of 2.5–10.     

Zn(II)‐Selective Membrane Electrode Based on Tetraazamacrocycle [Bzo2Me2Ph2(16)hexaeneN4]

A PVC membrane electrode using [Bzo₂Me₂Ph₂(16)hexaeneN₄] ( I ) as ionophore, oleic acid as lipophilic additive and o‐nitrophenyloctyl ether as plasticizer has been investigated as Zn(II)‐selective electrode. The membrane incorporating 34.9% (w/w) PVC, 2.3% I , 4.7% OA and 58.1% o‐NPOE gave linear response over the concentration range 2.82×10^?6?1.0×10^?1 M with a Nernstian slope of 28.5±0.2 mV/decade of concentration with a detection limit of 2.24×10^?6 M (0.146 ppm) and showed a response time of less than 10 s and could be used in pH range 2.5–8.5. High selectivity was obtained over a wide variety of metal ions. The proposed electrode was successfully used as an indicator electrode in potentiometric titration of zinc ions with EDTA and for determination of zinc in real samples.     

Fabrication of a Nitrate Selective Electrode for Determination of Nitrate in Fertilizers by Using Flow Injection Analysis System

A nitrate ion selective electrode (nitrate-ISE) based on pyrrole modification on a common pencil lead was proposed. The lab-made nitrate-ISE was easily constructed by pyrrole polymerization with nitrate ion as the dopant using cyclic voltammetry. The fabricated nitrate-ISE was then coupled with flow injection analysis (FIA) for an automatic system. The flow potentiometry provided working range of 1x10^-4 to 4x10^-3 mol L^-1 of nitrate and allowed sample throughput up to 50 samples h^-1. Linear regression analysis showed good agreement (r²=0.9961) with Nernstian response. This system was applied to determine nitrate-nitrogen (nitrate-N) in fertilizer samples.