基于酞菁铜衍生物为载体的电极对水杨酸根的选择性电位响应

本文以2,9,16,23-四硝基酞菁铜(II) (Cu(II)TNPc) 和2,9,16,23-四氨基酞菁铜(II) (Cu(II)TAPc) 为载体制备PVC聚合膜,构建了水杨酸根选择性电极,并探讨了该电极的选择性响应性能。研究了增塑剂的性质、载体的含量及阴、阳离子添加剂对电极电位响应的影响。结果表明,基于Cu(II)TNPc为载体的PVC膜电极对水杨酸根 (Sal－) 呈现出优先选择性电位响应。具有最佳电位响应的电极的膜组成是：(w/w) 3.0% Cu(II)TNPc,67.0% o-NPOE,29.5% PVC和0.5% NaTPB。基于该组成的电极的线性响应范围为1.0×10－1－9.0×10－7 mol·L－1,检测下限为7.2×10－7 mol·L-1,斜率为－59.8±0.5 mV/decade;其响应快速,稳定性好,适宜的pH范围是3.0－7.0。并成功运用于了实际样品中水杨酸含量的测定,获得令人满意的结果。     

Be(II) Graphite Coated Membrane Sensor Based on a Recently Synthesized Benzo‐9‐Crown‐3 Derivative

A highly sensitive and selective membrane electrode with 9‐crown‐3 derivative (CD) as ionophore, potassium tetrakis‐(p‐chlorophenyl) borate as anionic additive (KTB), acetophenone (AP) as solvent mediator was prepared and investigated as a Be(II) sensor. The best performance was observed with the membrane having the percent ratio 30% PVC: 8% CD: 6% KTB: 56% Acetophenone. The poly(vinyl chloride) PVC membrane containing 9‐crown‐3 derivative (CD) directly coated on a graphite electrode, shows a Nernstian response for Be(II) ions over a very wide concentration range (1.0×10^?1?1.0×10^?7 M) with a detection limit of 8.0×10^?8 M (ca. 0.72 ng/mL). It has a fast response time of ca. 20 s and can be used for at least 10 weeks without any major deviation in potential. The proposed sensor exhibits very good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. The proposed sensor was used as end point indicator electrode in the titration of Be(II) ions with EDTA. It was also applied to determination of Be(II) in real sample.     

An All‐solid‐state Polymeric Membrane Ca2+‐selective Electrode Based on Hydrophobic Alkyl‐chain‐functionalized Graphene Oxide

An all‐solid‐state polymeric membrane Ca²⁺‐selective electrode based on hydrophobic octadecylamine‐functionalized graphene oxide has been developed. The hydrophobic composite in the ion‐selective membrane not only acts as a transduction element to improve the potential stability for the all‐solid‐state Ca²⁺‐selective electrode, but also is used to immobilize Ca²⁺ ionophore with lipophilic side chains through hydrophobic interactions. The developed all‐solid‐state Ca²⁺‐selective electrode shows a stable potential response in the linear range of 3.0×10⁻⁷–1.0×10⁻³ M with a slope of 24.7±0.3 mV/dec, and the detection limit is (1.6±0.2 )×10⁻⁷ M (n =3). Additionally, due to the hydrophobicity and electrical conductivity of the composite, the proposed all‐solid‐state ion‐selective electrode exhibits an improved stability with the absence of water layer between the ion‐selective membrane and the underlying glassy carbon electrode. This work provides a simple, efficient and low‐cost methodology for developing stable and robust all‐solid‐state ion‐selective electrode with ionophore immobilization.     

1‐Pyrrolidine Dicarbodithioate Based Electrodes for Determination of Iron(III) in Lubrication Oil

The lipophillic ammonium salt of 1‐pyrrolidine dicarbodithioic acid (PCDT) (I) was introduced as a new selective ionophore for an iron selective electrode. In addition, the effect of immobilization of 18‐crown‐6 (18CE6) (membrane type‐II), on the electrode performance was discussed. The slope of the PCDT‐based (I) electrode was (20 mV/decade). The linear concentration range was (10^?5–10^?1 M) after one day doping. The detection limit for electrode type‐(II) was (1.3×10^?6 M). For membrane with only 18CE6 (type‐III) the linear range and the detection limit were improved (10^?5–10^?1 M and 3.2×10^?6 M, respectively). The pH‐range was between 5–11 for type‐II, and III electrodes, while it was 7–11 for type‐I electrode. Most of the common cations were tested for the evaluation of the electrode selectivity with correlation to the ionic radii of the tested cations. Among them only Ag⁺ and Pb²⁺ were the real interference for type‐III electrode. Application of using the electrode for the determination of iron in lubrication oil samples was performed with RSD (1.77–2.7%) and (1.01–2.3%) for type‐II and III electrodes, respectively. The corresponding recovery ranges were (93.0–99.9%) and (96.3–100%). The obtained results were compared to those of an atomic absorption spectrophotometric method.     

Comparative Studies of Tridentate Sulfur and Nitrogen‐Containing Ligands as Ionophores for Construction of Cadmium Ion‐Selective Membrane Sensors

New polymeric membrane cadmium‐ion selective sensors have been prepared by incorporating nitrogen and sulfur containing tridentate ligands as the ionophores into the plasticized PVC membranes. Poly(vinyl chloride) (PVC) based membranes of potassium hydrotris[N‐(2,6‐xylyl)thioimdazolyl) borate] (KTt^2,6‐xylyl) and potassium hydrotris(3‐phenyl‐5‐methylpyrazolyl) borate (KTp^Ph,Me) with sodium tetraphenyl borate (NaTPB) as an anionic excluder and dibutylphthalate (DBP), tributylphthalate (TBP), dioctylsebacate (DOS), and o‐nitrophenyloctyl ether (o‐NPOE) as plasticizing solvent mediators were investigated in different compositions. KTt^2,6‐xylyl was found to be a selective and sensitive ion carrier for Cd(II) membrane sensor. A membrane composed of KTt^2,6‐xylyl:NaTPB:PVC:DBP with the % mole ratio 2.3 : 1.1 : 34.8 : 61.8 (w/w) works well over a very wide concentration range (7.8×10^?8–1.0×10^?2 M) with a Nernstian slope of 29.4±0.2 mV/decades of activity between pH values of 3.5 to 9.0 with a detection limit of 4.37×10^?8 M. The sensor displays very good discrimination toward Cd(II) ions with regard to most common cations. The proposed sensor shows a short response time for whole concentration range (ca. 8 s). The effects of the cationic (tetrabutylammonium chloride, TBC), anionic (sodium dodecyl sulfate, SDS) and nonionic (Triton X‐100) surfactants were investigated on the potentiometric properties of proposed cadmium‐selective sensor. The proposed sensor based on KTt^2,6‐xylyl ionophore has also been used for the direct determination of cadmium ions in different water samples and human urine samples.     

Development and Optimization of an Ion‐selective Electrode for Serotonin Detection

Our studies are focused on the development of novel potentiometric sensors for the quantification of the neurotransmitter serotonin. Therefore, ion‐selective electrodes based on plasticized PVC membranes are applied. The electroactive part of the membrane consists of an ion pair complex formed between the protonated analyte and a carborane anion [Co(1,2‐C₂B₉H₁₁)₂]⁻. The analytical performance of the electrode was studied regarding sensitivity, concentration range, limit of detection and potential stability. The ion‐selective electrodes were optimized with respect to the material of the transducing element, as well as the membrane thickness and its composition. Stable, all solid state ISEs could be developed, using the non‐polar plasticizer NPOE and a graphite rod with high surface area as transducing element. We thus achieved a near Nernstian response over three decades of concentration (2.25⋅10^‐5‐1.00⋅10^‐2 M) and a limit of detection in the μ‐molar range for the optimized electrodes. The electrodes could successfully be miniaturized using carbon based screen printed electrodes.     

Crown Ethers Bearing 18C6 Unit; Sensory Molecules for Fabricating PVC Membrane Lead Ion‐selective Electrodes

Crown ethers bearing 18C6 unit 18‐crown‐6 (18C6), dicyclohexyl18‐crown‐6 (DC18C6) and dibenzo18‐crown‐6 (DB18C6) have been examined as ion sensing materials for fabricating lead ion‐selective potentiometric sensors. Best performance of the electrode based upon 18C6 ionophore was achieved by using a membrane including 9% ionophore, 30% polyvinyl chloride (PVC), 2% oleic acid and 59% dibutylphthalate (DBP). The optimum composition for the sensors based on DC18C6 and DB18C6 was provided by the compositions: 9% DC18C6, 30% PVC, 1.5% sodium tetraphenyl borate (NaTBP), 59.5% DBP; and 5.9% DB18C6, 29.7% PVC, 2.5% NaTBP and 61.9% DBP, respectively. The linear response range of the electrode based on 18C6 (1 × 10^‐6‐1 × 10^‐3 M) differs from that presented by the DC18C6‐ and DB18C6‐based electrodes (1 × 10^‐5‐1 × 10^‐2 M). All the sensors were shown rapid response time (<12 s). The detection limit of the electrodes varies as 5.6 × 10^‐7, 6.3 × 10^‐6 and 7.1 × 10^‐6 M, for 18C6‐, DC18C6‐ and DB18C6‐based electrodes, respectively. The selectivity of the electrodes towards lead ions over some mono‐, di‐ and trivalent metal ions was evaluated. The lifetime of the electrode based on DC18C6 or DB18C6 ionophores was found to be more than three months, while it was shorter for 18C6‐based electrode. The application of the electrodes in aqueous samples was assessed.     

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.     

Ion-selective sensors for determining Au(CN)<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> with membranes based on the ionic liquid tetradecylphosphonium dicyanoaurate

A polymeric membrane for an ion-selective electrode is proposed on the basis of supramolecular systems including a polymeric compound (polyvinyl chloride, PVC) and an ionophore (ionic liquid tetradecylphosphonium dicyanoaurate) in which ionic liquid is simultaneously used as a PVC plasticizer. The selectivity, linear response range, and potential stability of ion-selective electrodes with the optimum membrane composition are measured. The detection limit for Au(I) with the developed electrode is 4.5 × 10^?7 M.     

PVC‐Based on Thiopyrilium Derivatives Membrane Electrodes for Determination of Histamine

This study describes novel histamine‐selective electrodes, having their basis on thiopyrilium (TP) derivatives as suitable ionophores. The electrodes were prepared by incorporating the TP derivatives into plasticized poly(vinyl chloride) (PVC) membranes. These electrodes demonstrate high selectivity as far as the histamine response is considered, as compared with many common inorganic anions and other kinds of amino acids. The influence of membrane composition, pH and the effect of lipophilic cationic and anionic additives on the response characteristics of the electrode were investigated. The resulting sensor based on 2,6‐bis(4‐dimethyl amino phenyl)‐4‐phenyl thiopyrilium perchlorate (TP4) responds to histamine in a wide concentration range from 5.0 × 10^?6 to 1.0 × 10^?1 M with a slope of 54.8 ± 0.6 mV decade^?1 and detection limit of 3.0 μ mol L^?1 (～0.3 ppm). The electrode illustrates fast response time and good long‐term stability (more than 2 months). The ability to design histamine‐selective electrodes based on new thiopyrilium derivatives and both to alter selectivity and improve the response characteristics through structural changes to the charged ionophore, has been investigated. The prepared electrode was used for the determination of histamine in a synthetic human serum sample. Consequently, satisfactory recovery results were obtained over a wide concentration range of histamine.     

A Copper(II) Ion‐Selective Potentiometric Sensor Based on N,N′,N″,N′′′‐Tetrakis(2‐pyridylmethyl)‐1,4,8,11‐tetraazacyclotetradecane in PVC Matrix

The simple PVC‐based membrane containing N,N′,N″,N′′′‐tetrakis(2‐pyridylmethyl)‐1,4,8,11‐tetraazacyclotetradecane (tpmc) as an ionophore and dibutyl phthalate as a plasticizer, directly coated on a glassy carbon electrode was examined as a new sensor for Cu²⁺ ions. The potential response was linear within the concentration range of 1.0×10^?1–1.0×10^?6 M with a Nernstian slope of 28.8 mV/decade and detection limit of 7.0×10^?7 M. The electrode was used in aqueous solutions over a wide pH range (1.3–6). The sensor exhibited excellent selectivity for Cu²⁺ ion over a number of cations and was successfully used in its determination in real samples.     

Homooxacalix[3]arene Derivatives as Ionophores for Serotonin‐Selective Membrane Electrodes

Homooxacalix[3]arene derivatives are effective ionophores for constructing serotonin‐selective membrane electrodes. An electrode based on one of the derivatives, tris(methoxyphenylpropyloxy)hexahomooxacalix[3]arene‐triethyl ether, with potassium tetrakis(p‐chlorophenyl)borate (20 mol% relative to the ionophore) as an ionic additive and bis(2‐ethylhexyl) sebacate as a solvent mediator in a poly(vinyl chloride) membrane matrix, displayed much better selectivity for serotonin than for various organic ammonium ions and inorganic cations. The electrode exhibited a near‐Nernstian response to serotonin in the concentration range of 2×10^?4 to 1×10^?2 M with a slope of 56.4 mV per concentration decade in physiological saline containing 150 mM NaCl and 10 mM Na₂HPO₄/NaH₂PO₄ (pH 7.4). The limit of the detection was 8×10^?5 M. The selectivity pattern of this electrode was quite different from that of an electrode using calix[6]arene‐hexaacetic acid hexaethyl ester, a well‐known ionophore for primary organic ammonium ions, which did not induce an enhanced response to serotonin. The developed electrode was used for the active loading of serotonin in liposomes induced by transmembrane pH gradients.     

Semifluorinated Polymers as Ion‐selective Electrode Membrane Matrixes

Most commercially available fluorous polymers are ill suited for the fabrication of ion‐selective electrode (ISE) membranes. Therefore, we synthesized semifluorinated polymers for this purpose. Ionophore‐free ion‐exchanger electrodes made with these polymers show a selectivity range (≈14 orders of magnitude) that is nearly as wide as found previously for liquid fluorous ion‐exchanger electrodes. These polymers were also used to construct ISE membranes doped with fluorophilic silver ionophores. While the resulting ISEs were somewhat less selective than their fluorous counterparts, the semifluorinated polymers offer the advantage that they can be doped both with fluorophilic ionophores and traditional lipophilic ionophores, such as the silver ionophore Cu(II)‐I (o ‐xylylenebis[N,N ‐diisobutyldithiocarbamate]). We also cross‐linked these polymers, producing very durable membranes that retained broad selectivity ranges. K⁺ ISEs made with the cross‐linked semifluorinated polymer and the ionophore valinomycin showed selectivities similar to those of PVC membrane ISEs but with a superior thermal stability, the majority of the electrodes still giving a theoretical (Nernstian) response after exposure to a boiling aqueous solution for 10 h.     

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.     

Highly Selective Potentiometric Oxalate Ion Sensors Based on Ni(Ⅱ) Bis-(m-aminoacetophenone)ethylenediamine

A plasticized PVC (polyvinyl chloride) membrane based oxalate ion selective electrode has been developed by using the condensation product of m‐aminoacetophenone and ethylenediamine. The transition metal complexes of the ligand N,N′‐bis(m‐aminoacetophenene)ethylenediamine (L) were synthesized and incorporated as ionophore for the synthesis of oxalate ion selective electrodes. Most appropriate result in terms of dynamic range, detection limit and response behavior was determined for the Ni(II) bis‐(m‐aminoacetophenone)ethylenediamine complex. The electrode demonstrated higher selectivity for oxalate ion with improved performance as compared to other carriers reported in past. The electrode shows Nernstian slope of (?28.5±0.4) mV·decade^?1 with improved linear range of 1×10^?1?1×10^?7 mol·L^?1, with a comparatively lower detection limit in the pH range of 5–10.5, giving a relatively fast response within 10 s and reasonable reproducibility. The selectivity coefficient was calculated using matched potential method and fixed interference method. The lifetime of the electrode was found to be nearly 2 months. The response mechanism and the interaction of oxalate ion with the complexes have been discussed by UV‐visible spectroscopic technique. Further the electrode was also successfully applied to determine the oxalate content in water samples.     

Solid‐contact Acetate‐selective Electrode Based on a 1,3‐bis(carbazolyl)urea‐ionophore

The construction and study of solid‐contact acetate‐selective electrodes is described using a 1,3‐bis(carbazolyl)urea derivative as a neutral hydrogen‐bonding ionophore and poly(3,4‐ethylenedioxythiophene) as the solid contact. It was shown recently that this ionophore binds acetate (logK_ass=4.98) that is used as primary ion in this study. The electrodes show linearity over the activity range of 10^?4.50–10^?1.10 with a sub‐Nernstian slope of ?51.3 mV per decade and a detection limit of 10^?5.00. The anion‐selectivity pattern of these electrodes deviates markedly from the Hofmeister pattern. When adding ionophore to the membrane the logarithm of the selectivity coefficient (logK) for SCN^? decreased from 6.5 to 1.2, logK for I^? decreased from 5.7 to 0.9, logK for NO₃^? decreased from 4.3 to 0.6 and logK for Br^? decreased from 3.3 to 0.1. The selectivity coefficients of hydrophilic anions such as Cl^?, F^?, HPO₄^2?, and SO₄^2? are significantly lower than in case of the ionophore‐free membrane. It was discovered that the constructed electrodes are also relatively selective to bicarbonate. This work is an important step towards the further development of solid‐contact anion‐selective electrodes.     

Amide and Acyl‐Hydrazine Functionalized Calix[4]arenes as Carriers for Hydrogen Phosphate Selective Electrodes

Anion‐selective solvent polymeric membrane based on hydrogen bond‐forming, neutral ionophores with amide or acyl‐hydrazine groups are described. The use of the two calix[4]arenes results in anion‐selective electrodes with a selectivity for phosphate. The electrodes of the optimum characteristic have the composition of 1 wt% ionophore, 66 wt% o‐NPOE, 33 wt% poly (vinyl chloride) (PVC) and TDMACl (15 or 30 mol% relative to the ionophore 1 and 2 , respectively). The optimized membrane electrodes show Nernstian responses towards monohydrogen phosphate (?29.1 and ?29.3 mV/decade) based on ionophore 1 and 2 , respectively, in a wide concentration range (1.0×10^?5 to 1.0×10^?2 or 1.0×10^?5 to 1.0×10^?1 M). The selectivity coefficients are determined with the fixed interference method and the activity ratio method. The electrodes display an anti‐Hofmeister series selectivity pattern and highly selective for HPO₄^2? over Cl^?, Br^?, CH₃COO^?, NO₃^? and SO₄^2?. The lifetime of the electrodes is at least 1 month and their response time is found to be 25 s. The proposed sensors could be put to analytical use both by direct potentiometry as well as potentiometric titration.     

Ion‐Selective Electrodes for Thiocyanate Based on the Dinuclear Zinc(II) Complex of a Bis‐N,O‐bidentate Schiff Base

An ion selective electrode based on the dinuclear complex formed by two zinc(II) ions and two molecules of the bis‐N,O‐bidentate Schiff base 2,2′‐[methylenebis(4,1‐phenylenenitrilomethylidyne)]bisphenol exhibits thiocyanate selectivity with a good discrimination of nitrite, nitrate, and azide. The selectivities of electrode membranes with various compositions indicate that this potentiometric selectivity is based on the formation of a 1 : 1 complex between the thiocyanate anion and the dinuclear ionophore. The 2 : 1 ratio of thiocyanate ions and the dinuclear ionophore that results from higher ratios of cationic sites and ionophore worsens the selectivity, suggesting that binding of a thiocyanate to both zinc(II) centers of the dinuclear ionophore is not favorable. Interestingly, the selectivity patterns of these electrodes differ radically from that of a highly sulfate selective electrode based on a compound reported previously to be the analogous mononuclear 1 : 1 complex of zinc(II) and the same Schiff base. It is suggested that the previously reported 1 : 1 complex with zinc(II) may indeed have been a polymer of the same elemental composition.     

Highly Selective and Sensitive Copper(II) Membrane Sensors Based on 6‐Methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one as a New Neutral Ionophore

A new Cu(II) ion‐selective PVC membrane sensor based on 6‐methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one (MATTO) as an excellent sensing material was developed. The electrode exhibits a Nernstian slope of 29.2±0.4 mV per decade over a very wide concentration range between 1.0×10^?1 and 1.0×10^?6 M, with a detection limit of 4.8×10^?7 M (30.5 ng/mL). The sensor possesses the advantages of short conditioning time, fast response time (<10 s), and especially, very good selectivity towards transition and heavy metal, and some mono, di and trivalent cations. The proposed electrode was successfully applied to the determination of copper in wastewater of copper electroplating samples and as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA.     

Highly Selective and Sensitive Triiodide PVC‐Membrane Electrode Based on a New Charge‐Transfer Complex of Bis(2,4‐Dimethoxybenzaldehyde)butane‐2,3‐Dihydrazone with Iodine

In this work, a highly selective membrane triiodide sensor based on a new charge‐transfer complex of bis(2,4‐dimethoxybenzaldehyde)butane‐2,3‐dihydrazone with iodine (Iodide Charge Transfer complex: ICT) as membrane carrier is introduced. The influences of five different solvent mediators on sensitivity and selectivity of the proposed sensor were considered. The best performance was obtained with the membrane composition containing 30% poly (vinyl chloride), 63% DBP, 5% ICT and 2% HTAB. The electrode shows a Nernstian behavior over a very wide triiodide ion concentration range (1.0 × 10^?7‐1.0 × 10^?2 M), and a detection limit value of 8.0 × 10^?8 M. The effect of pH on the potentiometric response of the sensor was also studied, and it was found that the response of the electrode is independent of the pH of the solution in the pH range of 4.0–10. The proposed sensor has a very fast response time (< 12 s), and good selectivities relative to a wide variety of common inorganic and organic anions, including iodide, acetate, bromide, chloride, fluoride, nitrite, nitrate, sulfite, sulfate, cyanide and thiocyanate. In fact the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in the potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.