New metal complex systems as electrode active components of ion selective electrode membranes

New donor-acceptor 3d-transition metal complexes were synthesized and the cobalt and nickel complexes were studied by X-ray diffraction; CIF files CCDC no. 1516693 (III(Ni)) and 1516694 (III(Co)). The crystal structure details of the reactants were discussed. The proposed compounds were tested as the active components of ion selective electrode membranes for determination of thiocyanate ions. The selectivity of the SCN-SE with metal complex-based membranes depends on the ligand structure and the central metal ion type. The proposed electrode is suitable for determination of thiocyanate ions in the presence of sulfate, chloride, nitrate, nitrite, bromide, and iodide ions.     

The synthesis of poly(hydroxamic acid) from poly(acrylamide)

Poly(hydroxamic acid) in gel or water soluble from was prepared from the reaction of poly(acrylamide) and hydroxylamine in basic aqueous solution (pH > 12) at room temperature. The polymers were composed of 70% hydroxamic acid groups, less than 5% carboxylic acid groups, and 25% unreacted amide groups. The polymers exhibited high affinity to iron(III) and copper(II) in the pH range of 1 to 5 with a high binding rate. A binding of 3 mmol/g for both metals was achieved. Preliminary tests demonstrated the urease inhibitory activity of both linear and crosslinked poly(hydroxamic acids).     

A carbon nitride electrode for highly selective and sensitive determination of lead(II)

We have constructed a carbon nitride electrode modified with a bismuth film and show that it can be used for the electroanalysis of lead(II) by differential pulse anodic stripping voltammetry. The combination of such materials is shown to greatly improve the sensing capability of the electrode. Under the optimal conditions, the electrochemical response of the modified electrode is linearly related to the concentration of Pb(II) in the 6 – 1,000 nM concentration range (R = 0.9983). The detection limit is 2.0 pM (at an SNR of 3), and the sensitivity is 8 times better of that of respective graphite electrodes. The sensor enables rapid, highly sensitive, continuous, and environmentally friendly determination of trace levels of Pb(II) at affordable costs.

Copper(II) ion selective electrode based on a newly synthesized Schiff-base chelate

A new Cu (II) ion-selective electrode has been fabricated in poly (vinyl chloride) matrix based on a recently synthesized Schiff-base chelate. The addition of sodium tetraphenylborate (NaTPB) and various plasticizers viz. TBP, TEHP, DOS, and CN have been found to substantially improve the performance of the electrode. The membrane of various compositions of the ionophore (I) were investigated and it was found that the best performance was obtained with the membrane having (I): PVC: NaTPB: CN in the ratio 4: 140: 3: 80 (mg). The electrode exhibits a Nernstian response over a wide concentration range (1.9 × 10⁻⁶–1.0 × 10⁻¹ M) with 30.0 mV/decade of concentration between pH 3.0 and 7.5. The response time of the electrode is about 12 s and it can be used over a period of 3 months without any divergence in potential. The potentiometric selectivity coefficient values as determined by fixed interference method indicate excellent selectivity for Cu²⁺ ions over interfering cations. The electrode has also been used successfully in partially non-aqueous media having a 25% (v/v) methanol, ethanol or acetone content without showing any considerable change in the value of slope or working concentration range. The electrode has been used in the potentiometric titration of Cu²⁺ with EDTA.     

A lead(II) toluene complex

A well-defined intermolecular toluene complex of lead(II) supported by a pincer-type saNHC (saturated N-heterocyclic carbene) ligand was prepared through deprotonation of the bis(imidazolinium) salt with Pb[N(SiMe₃)₂]₂ or metalation of the free carbene and subsequent salt metathesis with Tl(OTf), followed by crystallization from toluene. Combined computational and experimental results indicate that noncovalent interactions with the lead atom (σ-sss-hole type interaction, dispersion) and the diisopropylphenyl side groups of the ligand (dispersion) stabilize the complex.     

A bromide selective polymeric membrane electrode based on Zn(II) macrocyclic complex

A novel bromide ion-selective PVC membrane sensor based on 2,3,10,11-tetraphenyl-1,4,9,12-tetraazacyclohexadeca-1,3,9,11-tetraene zinc(II)complex (I) as carrier has been developed. The electrode exhibited wide working concentration range 2.2 × 10⁻⁶ to 1.0 × 10⁻¹ M and a limit of detection as 1.4 × 10⁻⁶ M with a Nernstian slope of 59.2 ± 0.5 mV per decade. The response time of electrode was 20 s over entire concentration range. The electrode possesses the advantages of low resistance, fast response and good selectivities for bromide over a variety of other anions and could be used in a pH range of 3.5–9.5. It was successfully used as an indicator electrode in the potentiometric titration of bromide ions with silver ion and also in the determination of bromide in real samples.     

A novel chemically modified carbon paste electrode based on a new mercury(II) complex for selective potentiometric determination of bromide ion

A new modified carbon paste electrode based on a recently synthesized mercury (II) complex of a pyridine containing proton transfer compound as a suitable carrier for Br⁻ ion is described. The electrode has a linear dynamic range between 3.00×10⁻² and 1.0×10⁻⁵ M with a near-Nernastian slope of 61.0±0.9 mV per decade and a detection limit of 4.0×10⁻⁶ M (0.32 ppm). The potentiometric response is independent of the pH of the solution in the pH range 4.0–8.3. The electrode possesses the advantages of low resistance, fast response and good over a variety of other anions. It was applied as an indicator electrode in potentiometric titration of bromide ions and for the recovery of Br⁻ from tap water.     

Iodide ion selective poly(aniline) solid contact electrode based on quinine-cu ionophores

Iodide ion selective poly(aniline) solid contact electrode based on quinine-Cu ionophore as a sensing material has been successfully developed. The electrode exhibits good linear response of 52.0 mV/decade (at 20 ± 0.2°C, r ² = 0.9998) within the concentration range of 1 × 10^−6.4–1 × 10^−1.0 M KI. The composition of this electrode was quinine-Cu 2.0: PVC 30.0: bis(2-ethylhexyl)sebacate 68.0 (mass). This plasticizer provides the best response characteristics. The electrode shows good selectivity for iodide ion in comparison with any other anions and is suitable for use with aqueous solutions of pH 3.3–9.4. The standard deviations of the measured EMF difference were ±1.4 and ±1.3 mV for iodide sample solutions of 1.0 × 10⁻² M and 1.0 × 10⁻³ M, respectively. The stabilization time was less than 10 min and response time was less than 15 sec.     

A selective voltammetric detection for dopamine using poly (gallic acid) film modified electrode

<正>The electrochemistry behavior of dopamine was investigated by cyclic voltammetry and differential pulse voltammetry at a poly (gallic acid) film modified glassy carbon electrode.Two electrons and two protons participated in the diffusion-controlled electrocatalytic oxidation of dopamine with a diffusion coefficient of 2.186×10~(-5) cm~2/s.The interference of ascorbic acid with the determination of dopamine could be efficiently eliminated.This work provided a simple approach to selectively and sensitively detect dopamine in the presence of high concentration of ascorbic acid.     

Synthesis and properties of poly(hydroxamic acid) from crosslinked poly(methacrylate)

Poly(hydroxamic acid) chelating ion-exchange resin was prepared from crosslinked poly(methacrylate) beads. The starting polymer was prepared by a suspension polymerization of methacrylate and divinyl benzene. Conversion of the ester groups into the hydroxamic acid was carried out by treatment with hydroxylamine in an alkaline solution. Hydroxamic acid capacity of the product was 2.71 mmol/g. The resin exhibited high affinity towards Fe(III) and Pb ions and its capacities for Fe(III), Pb, Cu, Ni and Co ions were pH dependent. The ability of the resin to carry out the separation of Fe(III)CuCo/Ni and PbNi ions is also reported.     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium-Schiff's base complex

A PVC membrane electrode based on a cadmium-salen (N,N'-bis-salicylidene-1,2-ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5-11.0. It has a linear response to thiocyanate from 1.0 x 10(-6) to 1.0 x 10(-1) mol L(-1) with a slope of 59.1 +/- 0.2 mV per decade, and a detection limit of 7 x 10(-7) mol L(-1). This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.     

A new lead(II)-selective PVC-coated graphite rod electrode based on a Schiff base complex.

A new lead(II)-selective electrode has been developed based on bis(acetylacetone)-p-phenylenediamine-lead(II) [LPb(NO3)2]H2O complex ionophore as a sensing material, dioctylphthalate (DOP) as a solvent mediator and PVC as a matrix. This electrode exhibits a linear Nernstian response over the concentration range of 1 x 10(-5)-1 x 10(-1) mol l(-1) of Pb(II) cation, with a cationic calibration slope of 30.0 +/- 0.2 mV/concentration decade and a detection limit of 2 x 10(-6) mol l(-1) (0.40 ppm). It has a fast response time and can be used for a period of 2 months without any divergence in potentials. The proposed electrode reveals a good selectivity for Pb(II) over a wide variety of other tested cations and could be used in the pH range of 4-8. It was successfully used for direct determination of Pb(II) concentration in some samples. The obtained results show a good agreement with those obtained by an atomic absorption spectrometric method. The average recovery obtained is 96.5 +/- 0.5% with standard deviation of 1.2% (n = 8).     

Zirconium ion selective electrode based on bis(diphenylphosphino) ferrocene incorporated in a poly(vinyl chloride) matrix

A novel potentiometric zirconium - PVC matrix membrane sensor incorporating bis(diphenylphosphino) ferrocene as an electroactive material and tris(2-ethylhexyl)phosphate as solvent mediator is described. In mixed acetate buffer solution of pH 4.8, the sensor displays a rapid and linear response for zirconium ion over the concentration range 1.0 × 10⁻¹ to 1.0 × 10⁻⁷ mol L⁻¹ with a good slope of 59.7 ± 0.3 mV per decade and detection limit 1.8 × 10⁻⁸ mol L⁻¹. The best performance was obtained with membrane composition 33% PVC, 65% TEHP, 1% NaTPB and 1% ionophore. The proposed electrode revealed excellent selectivity for zirconium ion over a wide variety of alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.15-7.8. The electrode was applied for at least 1 month without any considerable divergence in the potential responses. The practical utility of the electrode has been demonstrated by its use as an indicator electrode in the potentiometric titration of zirconium ions with sodium fluoride and in determination of zirconium ion in some alloy, tape and waste water samples.     

Mercury ion selective poly(aniline) solid contact electrode based on 2-mercaptobenzimidazol ionophore

A mercury(II) ion selective poly(aniline) solid contact electrode based on 2-mercaptobenzimidazol (2MBI) ionophore as a sulfur containing sensing material was successfully developed. The electrode exhibits a good linear response of 29.1 mV/decade (at 20 ± 0.2°C, r ² = 0.997) within the concentration range of 1 × 10^?2?1 × 10^?7 M Hg(II). The composition of this electrode was: ionophore 0.100, polyvinylchloride (PVC) 0.330, dibutylphthalate (DBP) 0.470, potassiumtetrakis(4-chlorophenyl)borate (KTpCIPB) 0.090, and oleic acid (OA) 0.010. A poly(aniline) solid contact electrode based on 2MBI with DBP and OA plasticizers exhibited the best response characteristics of the results obtained for similarly coated wire type electrodes and solid contact electrodes based on only one DBP plasticizer. The electrode shows good selectivity for mercury(II) ions in comparison with alkali, alkaline earth, transition and heavy metal ions. This electrode is suitable for use with aqueous solutions of pH 3.3?C8.0 and the standard deviation in the measured EMF difference was ±0.5 mV in a mercury nitrate sample solution of 1.0 × 10^?2 M and ±1.1 mV in a mercury nitrate sample solution of 1.0 × 10^?3 M. The stabilization time was less than 15 min and the response time was less than 33 s. The electrode was applied as a sensor for the determination of Hg(II) content in a sea water sample and some amalgam alloys. The results show good correlation with data obtained by atomic absorption spectrometry.     

离子选择性电极法测定聚合硫酸铁絮凝剂中的铅

无机高分子絮凝剂聚合硫酸铁(PFS)是我国最有前景的水处理剂之一,其应用领域广泛,除工业废水处理、市政污水处理外还应用于自来水净化处理。目前,制备聚合硫酸铁多采用工业废料,不可避免地含有不同量的铅。国家标准GB14591-1993规定,作为饮用水水处理剂PFS中的铅质量分数不得超过0.0010%。目前用于工业废水中铅量的测定方法有丁基罗丹明B光度法[1]、结晶紫光度法[2]等。光度法测定中必须进行萃取、离子交换、共沉淀等分离富集操作,这就大大增加了分析步骤和操作难度,使铅的吸光光度测定的应用受到一定的限制。最近罗平、郑怀礼等[3,…     

Titrimetric determination of trace sulfur in petroleum using a lead ion selective electrode

Summary A method for the determination of trace total sulfur in petroleum distillates is described. The petroleum sample is combusted using an oxyhydrogen burner. The combustion products are collected in 50 ml of absorber solution containing 10 mg of sodium nitrite and 0.444 mg of sodium sulfate. The excess nitrite is destroyed by boiling. After cooling, sufficient 1,4-dioxane is added to make a 50 volume % solution for the titration. The titration is carried out using –0.5amp polarizing current through a lead ion-selective electrode. Standardized (0.0025M) lead perchlorate is the titrant. The potential break at the endpoint is determined graphically from the titration curve and related to the total sulfur in the petroleum sample.

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Zusammenfassung Ein Verfahren zur Bestimmung von Spuren Gesamtschwefel in Erdöldestillaten wurde beschrieben. Die Probe wird in einer Knallgasflamme verbrannt, die Verbrennungsprodukte werden in 50 ml einer Absorptionslösung aufgefangen, die 10 mg Natriumnitrit und 0,444 mg Natriumsulfat enthält. Das überschüssige Nitrit wird durch Kochen zerstört. Nach dem Abkühlen setzt man der Flüssigkeit das gleiche Volumen Dioxan zu und titriert unter Verwendung einer für Bleiionen spezifischen Elektrode mit einem Polarisationsstrom von –0,5Amp. 0,0025-m Bleiperchlorat dient als Maßlösung. Der Potentialsprung beim Endpunkt wird graphisch ermittelt und entspricht dem Gesamtschwefelgehalt der Probe.

     

Determination of the stability constant of Np(V) fluoride complex using a fluoride ion selective electrode

Fluoride complexing of Np(V) has been studied using fluoride ion selective electrode (F-ISE). Free fluoride ion concentrations in the presence of Np(V) were measured at 0.1 and 1.0M ionic strength. The data were used to calculate the stability constant of the fluoride complex of Np(V) and the values obtained are reported here.     

A highly selective iodide electrode based on the bis(benzoin)-semiethylenediamine complex of mercury(II) as a carrier

A new PVC membrane electrode based on the bis(benzoin)-semiethylenediamine (BBSEA) complex of Hg(II) is described which exhibits excellent selectivity towards iodide, related to the unique interaction between the central Hg(II) and the iodide ion. The electrode has a linear response to iodide from 5 × 10^–7 to 5 × 10^–4 mol/L with a slope of 58 mV/dec.(20°C). The response characteristics were investigated in detail and the mechanism of the electrode was studied with AC impedance and quartz crystal microbalance (QCM) techniques. It can be used for iodide determinations in drug preparations.     

A highly selective iodide electrode based on the bis(benzoin)-semiethylenediamine complex of mercury(II) as a carrier

A new PVC membrane electrode based on the bis(benzoin)-semiethylenediamine (BBSEA) complex of Hg(II) is described which exhibits excellent selectivity towards iodide, related to the unique interaction between the central Hg(II) and the iodide ion. The electrode has a linear response to iodide from 5 × 10^–7 to 5 × 10^–4 mol/L with a slope of 58 mV/dec.(20°C). The response characteristics were investigated in detail and the mechanism of the electrode was studied with AC impedance and quartz crystal microbalance (QCM) techniques. It can be used for iodide determinations in drug preparations. Received: 29 January 1997 / Revised: 17 April 1997 / Accepted: 20 April 1997