Screen-printable sol-gel ceramic carbon composite pH sensor with a receptor zeolite

A screen-printable method is proposed to prepare a ceramic carbon composite sensor for pH determination. The pH-sensing membrane of the sensor is prepared by sol-gel, graphite powder and zeolite, in which zeolite is used as a receptor of proton. The fabrication of this ceramic carbon sensor includes three steps: preparing electrode slides, making a pH-sensing composite ink and screen-printing the ink on electrode slides. Optimum conditions for the ceramic carbon composite film are established, and characters of the pH electrode (stability, reproducibility, lifetime and conductivity) are examined comparing with glass pH electrodes. The Nernst response to pH of the sensor is in the range of pH 1-12 with a slope of 60 mV per pH. The sensor has been applied to pH measurements of samples and satisfactory results were obtained with R.S.D. of 0.18-1.25%.     

Determination of Fluoride Ions in Mouthwash Samples by a PVC Membrane Samarium(III) Sensor

Abstract

In this study, a new ion-selective electrode for Sm³⁺ is described, illustrating 2-[(E)-1-(1H-pyrrol-2-yl)methylidene]-1-hydrazinecarbothioamide (PMH) in a poly(vinylchloride) (PVC) membrane with nitrobenzene (NB) as a plasticizer and sodium tetraphenyl borate (NaTPB) as an anionic additive. The proposed sensor exhibited a Nernstian response for Sm³⁺ ions over a wide concentration range between 1.0 × 10^?2 and 1 × 10^?6 M, with a detection limit of 5.2 × 10^?7 M in the pH range of 4.2–8.5. Moreover, the sensor displayed the Nernstian slope of 19.8 ± 0.3 mV per decade, having a fast response time within 10 s over the entire concentration range. This electrode presented very good selectivity and sensitivity toward the Sm³⁺ ions over a wide variety of cations, including alkali, alkaline earth, transition-metal, and heavy-metal ions. It was used as an indicator electrode in the potentiometric titration of Sm³⁺ ions with EDTA. The membrane sensor was also applied to the determination of fluoride ions in mouthwash samples.     

Use of a poly(4,4′-diaminobiphenyl) chemically modified electrode as a pH sensor

A chemically modified electrode (CME) for use as a potentiometric pH sensor was constructed by electropolymerizing a poly(4,4′-diaminobiphenyl) coating on a platinum electrode. The resulting CME gave a linear response to pH in the range 1–12 with a slope of ?56 mV pH^?1. The CME functioned well in titration experiments and in pH measurements. No significant interference of a coexisting redox couple with the pH measurements was observed. The mechanism of the pH response of the CME is considered.     

Quantitative Analysis of Holmium Ion by a Ho3+ Ion‐Selective Sensor Based on a Symmetric Thio‐Schiff's Base

A poly(vinyl chloride) (PVC) membrane sensor for holmium ions was fabricated based on N‐[(Z)‐1‐(2‐thienyl)‐ methylidene]‐N‐[4‐(4‐{[(Z)‐1‐(2‐thienyl)methylidene]amino} phenoxy)phenyl] amine (TPA) as a new ion carrier, acetophenon (AP) as plasticizing solvent mediator and sodium tetraphenyl borate (NaTPB) as an anion excluder. The electrode shows a good selectivity towards Ho³⁺ ions respect to other inorganic cations, including alkali, alkaline earth, transition and heavy metal ions. The constructed sensor displays a Nernstian behavior (19.5±0.3 mV/decade) over the concentration range of 1.0×10⁻⁶ to 1.0×10⁻² mol·L⁻¹ with the detection limit of the electrode being 4.6×10⁻⁷ mol·L⁻¹ and very short response time (ca. 5 s). It has a useful working pH range of 3.2–9.8 for at least 8 weeks. The electrode was successfully applied as an indicator electrode for the potentiometric titration of a Ho³⁺ solution with EDTA and holmium determination in some alloys. The proposed sensor accuracy was studied by the determination of Ho³⁺ in mixtures of three different ions.     

聚苯胺修饰碳纤维针型复合微pH传感器

由电聚合法用聚苯胺修饰碳纤维电极作为ＰＨ敏感电极。把Ｋ３Ｆｅ（ＣＮ）６／Ｋ４Ｆｅ（ＣＮ）６体系填入医用注射针头内成为参比电极。把经聚苯胺修饰的碳纤维电极安置入该针型参比电极内构成复合针型微ｐＨ传感器。在ＰＨ ２～１２范围内，该传感器呈现超Ｎｅｒｎｓｔ响应，斜率为－７８ ｍＶ／ｐＨ；响应时间<１ｍｉｎ。该传感器成功地应用于在体ｐＨ测定以及水果内微区ｐＨ测定。     

Triiodide PVC Membrane Electrode Based on a Charge‐Transfer Complex of Iodine with Ditertbutyl‐Dicyclohexyl‐18‐Crown‐6

A new triiodide ion‐selective electrode based on a charge‐transfer complex of iodine with ditertbutyl‐dicyclohexyl‐18‐crown‐6 (t‐Bu)₂DC18C6 as membrane carrier was prepared. The electrode has a linear dynamic range from 6.3 × 10^?3‐5 × 10^?6 with a Nernstian response of 58.6 ± 1 mV decade^?1 and a detection limit of 1.3 × 10^?6 M. The response time of the sensor was 25 s. The membrane could be used for two months without any divergence in potentials. The electrode exhibits an anti‐Hofmeistetr selectivity sequence with a preference for triiodide at pH 2.0‐10.0. The response mechanism of the electrode was investigated by Uv‐Vis spectroscopic technique. The electrode can be used for the determination of ascorbic acid in orange juice.     

A Novel Sulfate Polymeric Membrane Sensor Based on a New Bis‐Pyrylium Derivative

A novel ion‐selective polymeric membrane sensor based on pyrylium‐4,4‐(1,4‐phenylen) bis[2,6‐bis(2‐naphthyl)]‐bis[tetrafluoroborate] (PBGNB) as an excellent sensing material is successfully developed. The electrode possesses the advantages of a very low detection limit (5.0×10^?8 M), a wide working concentration range (1.0×10^?8?1.0×10^?1 M) and specially, a high sulfate selectivity over most common organic and inorganic anions. The sensor displays Nernstian behavior (slope of 29.5±0.5 mV per decade) in a wide pH range (3.0–8.5). It shows a short response time in the whole concentration range (ca. 10 s). The electrode was used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions. The proposed sensor was successfully applied to the direct determination of salbutamol sulfate and paromomycin sulfate.     

A Novel Al(III)‐Selective Electrochemical Sensor Based on N,N′‐Bis(salicylidene)‐1,2‐phenylenediamine Complexes

A polyvinylchloride membrane sensor based on N,N′‐bis(salecylidene)‐1,2‐phenylenediamine (salophen) as membrane carrier was prepared and investigated as a Al³⁺‐selective electrode. The sensor exhibits a Nernstian response toward Al(III) over a wide concentration range (8.0×10^?7–3.0×10^?2 M), with a detection limit of 6.0×10^?7 M. The potentiometric response of the sensor is independent of the pH of the test solution in the pH range 3.2–4.5. The electrode possesses advantages of very fast response and high selectivity for Al³⁺ in comparison with alkali, alkaline earth and some heavy metal ions. The sensor was used as an indicator electrode, in the potentiometric titration of aluminum ion and in determination of Al³⁺ contents in drug, water and waste water samples.     

共价键合修饰壳聚糖pH传感器的研制

以共价键合的方法将壳聚糖修饰到玻碳电极上制成了pH传感器,探讨了该传感器的性能及作用机理.结果表明该传感器在pH 0.7～11.0的范围内电极电势与pH符合Nernst响应,斜率为58.3 mV/pH,可准确测定较高酸度溶液的pH,克服了玻璃pH传感器的"酸误差"的缺点.该传感器内阻小,易微型化,在一定的pH范围内对温度不敏感且具有较好的准确度和重现性,较快的响应速度.可用于雨水和饮料等实际样品溶液的pH的测定.     

Azide-selective sensor based on tripodal iron complex for direct azide determination in aqueous samples

A potentiometric azide-selective sensor based on the use of iron(III) hydrotris(3,5-dimethylpyrazolyl)borate acetylacetonate chloride [Tp^Me2Fe(acac)Cl] as a neutral carrier for an azide-selective electrode is reported. Effect of various plasticizers, viz. o-nitrophenyloctyl ether (o-NPOE), dioctylphthalate (DOP), dibutylphthalate (DBP), and benzylacetate (BA), and an anion excluder, hexadecyltrimethylammonium bromide (HTAB), with [Tp^Me2Fe(acac)Cl] complex in poly(vinyl chloride) (PVC) were studied. The best performance was obtained with a membrane composition of [Tp^Me2Fe(acac)Cl]/HTAB/DOP/PVC in a ratio of 5:2:190:100 (w/w). The sensor exhibits significantly enhanced selectivity toward azide ions over the concentration range 6.3 × 10⁻⁷ to 1.0 × 10⁻² M with a lower detection limit of 3.8 × 10^–7 M and a Nernstian slope of 59.4 ± 1.1 mV decade⁻¹. Influences of the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. Fast and stable response, good reproducibility, long-term stability and applicability over a wide pH range (3.5–9.0) are demonstrated. The sensor has a response time of 14 s and can be used for at least 45 days without any considerable divergence in the potential response. The proposed electrode shows fairly good discrimination of azide from several inorganic and organic anions. It was successfully applied to the direct determination of azide in orange juice, tea extracts and human urine samples.     

Efficient Synthesis of a New Podand and Application as a Suitable Carrier for Silver Ion‐Selective Electrode

A new podand of 1,1′‐thia‐bis‐[1‐(chloroethan‐2‐acetamid‐α‐oxy)] naphtol was synthesized and used as a suitable carrier for Ag⁺ PVC membrane electrode. The electrode exhibited linear response with a Nernstian slope of (59.5±0.8 mV/decade) within a wide concentration range of 1.0×10^?7 to 1.5×10^?2 mol L^?1 silver ions. The electrode had a fast response time of <10 s and detection limit of 8.6×10^?8 mol L^?1 with a working pH range from 3.7 to 9.0. The electrode was highly selective for Ag(I) ions over a large number of cations such as alkali, alkaline earth, and heavy metal ions. The proposed sensor has been applied as an indicator electrode for indirect determination of vitamin B₁ in tablets by determination of Cl^? ions in this compound with a standard solution of Ag(NO₃).     

Construction of a New Uranyl‐Selective Electrode Based on a New Ionophore: Comparison of the Effect Additive on Electrode Responses

A new plasticized PVC uranyl‐selective electrode based on a bis(2‐hydroxyacetophenone)ethylenediimine (BHAED) carrier by the direct coating of the membrane ingredients on the surface of a graphite disk electrode is reported. The electrode displayed high selectivity for uranyl ion toward a number of inorganic ions. The influence of the membrane compositions and pH, the effect of lipophilic cationic and anionic additives and plasticizer on the response properties of the electrode were investigated. The electrode exhibited a Nernstian slope of + 29.3 ± 1.2 for the uranyl ion concentration in the range of 5.0 × 10^?6 ?0.05 M with detection limits of approx. 2.0 μM. The potentiometric responses of the electrode are independent of pH over the range of 3.0–4.5 with satisfactory reproducibility. The sensor has response times of <5 s and can be used for at least 2 months without considerable divergence in potential.     

Novel potentiometric sensor for the determination of Cd2+ based on a new nano-composite

A novel ion selective carbon paste electrode for Cd²⁺ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd²⁺ carbon paste sensor for the successful determination of Cd²⁺ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF₆, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade^?1) toward Cd²⁺ ions in the range of 3.0?×?10^?8 to 1.0?×?10^?1?mol?L^?1 with a detection limit of 7.5?×?10^?9?mol?L^?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions.     

Determination of Hg(II) ions in water samples by a novel Hg(II) sensor,based on calix[4]arene derivative

A PVC membrane electrode for Hg(II) ions, based on a new cone shaped calix[4]arene (L) as a suitable ionophore was constructed. The sensor exhibits a linear dynamic in the range of 1.0 × 10^?6–1.0 × 10^?1 M, with a Nernstian slope of 29.4 ± 0.4 mV decade^?1, and a detection limit of 4.0 × 10^?7 M. The response time is quick (less than 10 s), it can be used in the pH range of 1.5–4, and the electrode response and selectivity remained almost unchanged for about 2 months. The sensor revealed comparatively good selectivity with respect to most alkali, alkaline earth, and some transition and heavy metal ions. It was successfully employed as an indicator electrode in the potentiometric titration of Hg²⁺ ions with potassium iodide, and the direct determination of mercury content of amalgam alloy and water samples.     

Study on Hydrogen Ion-Selective Solid Contact Electrodes Based on Decamethylcyclopentasiloxane

Hydrogen ion-selective solid contact electrode based on decamethylcyclopentasiloxane (DMCS) as ionophore was fabricated. The membrane solution was prepared by mixing DMCS, polyvinyl chloride (PVC), potassium tetrakis p-chlorophenyl borate (KTpClPB) and various plasticizers. The best performance was obtained with the sensor based on NPOE (o-nitrophenyl octyl ether) and the conducting polymer layer of poly(pyrrole), doped with NaClO₄. The electrode exhibited Nernstian-response in the range of pH 1.9–9.8 with a slope of 57.6 ± 0.2 mV per decade and fast response time within 15 s. This electrode showed good selectivity and was successfully used as an indicator electrode in the potentiometric titration.     

Determination of Pseudoephedrine Hydrochloride in Some Pharmaceutical Drugs by Potentiometric Membrane Sensor Based on Pseudoephedrine–Phosphotungstate Ion Pair

Abstract

An ion-selective electrode (ISE) was developed for the rapid determination of pseudoephedrine hydrochloride (PSEHCl) in pharmaceutical preparations. The electrode incorporates a PVC membrane with a pseudoephedrine–phosphotungstate ion pair complex. The influences of membrane composition, temperature, pH of the test solution, and the interfering ions on the electrode performance were investigated. The sensor exhibits a Nernstian response for pseudoephedrine hydrochloride ions over a relatively wide concentration range (1.0 × 10^?1 to 1.0 × 10^?5 mol L^?1) with a slope of 56.2 ± 0.5 mV per decade at 25°C. It can be used in the pH range 4.0–10.5. The isothermal temperature coefficient of this electrode amounted to 0.0009 V/°C. The membrane sensor was successfully applied to determination of PSEHCl in its tablets and syrup.     

Novel Dy(III) Sensor Based on a New Bis‐Pyrrolidene Schiff's Base

In this work a dysprosium [Dy(III)]‐selective solvent polymeric membrane sensor based on N,N‐bis(pyrrolidene) benzne‐1,2‐diamine, poly(vinyl chloride)(PVC), the plasticizer benzylacetate (BA), and anionic site is described. This sensor responds to Dy(III) activity in a linear range from 1.0×10^?5 to 1.0×10^?1 M, with a slope of 20.6±0.2 mV per decade and a detection limit of 6.0×10^?6 M at the pH range of 3.5–8.0. It has a fast response time of<20 s in the entire concentration range, and can be used for at least 2 months without any considerable divergence in the electrode potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in the potentiometric titration of fluoride ions and in determination of concentration of F ^– ions in some mouth washing solutions.     

A New Pentadentate S‐N Schiffs' Base as a Novel Ionophore in Construction of a Novel Gd(III) Membrane Sensor

We found that bis(thiophenal) pyridine‐2,6‐diamine (BPD) can be used as an excellent ion carrier to prepare a gadolinium‐selective PVC‐based membrane sensor. The use of oleic acid (OA) and potassium tetrakis(p‐chlorophenyl borate)(KTKpClPB), as anionic additives, and dibutyl phthalate (DBP), acetophenone (AP) and nitrobenzene (NB), as plasticizing solvent mediators was investigated. The best performance was observed with a membrane having the composition of 30% PVC; 62% BA; 5% BPD; and 3% KTKpClPB. The resulting sensor works well over a relatively wide concentration range (1.0×10^?6–1.0×10^?1 M) with a Nernstian slope of 19.4±0.4 mV per decade of gadolinium activity over a wide pH range (3.5–8.0). The limit of detection of the sensor is 7.0×10^?7 M (ca. 110 ng mL^?1). The proposed electrode shows excellent discriminating ability toward gadolinium ions with regard to common alkali, alkaline earth, transition, heavy metal ions, and specially, lanthanide ions. The proposed sensor was applied as an indicator electrode for titration of gadolinium ions with EDTA.     

TiO2‐modified Carbon Paste Electrode as a Sensor for the Assay of Weak Organic Acids/Bases and Complex Matrix Samples

The construction, general performance characteristics and analytical application of a titanium dioxide–modified carbon paste electrode sensitive to hydrogen ions, based on incorporation of titanium dioxide in a carbon paste matrix, is described. The proposed electrochemical sensor exhibits a linear response in the pH range from 2 to 10, at 25 °C, with a sub‐Nernstian slope. The value of a slope is in a direct correlation with the electrode composition – the optimum content of a titanium dioxide in carbon paste is 30 %. Titanium dioxide‐modified carbon paste electrode shows fast response time and reproducibility, confirmed by different compounds determination in both, individual and complex material, namely, in synthetic and real samples. Besides, the electrode shows high selectivity in the presence of the alkali and the alkaline earth ions as Na⁺, K⁺, Ca²⁺ or Mg²⁺. The standard deviation of the investigated acids (acetic, oxalic, 5‐sulfosalicylic, p‐toluensulfonic acid, and amino acid‐glycine) and bases (N,N′‐diphenylguanidine and collidine) is less than 1.3 %. The obtained data are compared with those obtained by using a conventional glass pH‐electrode under the same experimental conditions and indicate a high correlation between them.     

Glucose Biosensor Based on Oxygen Electrode Part IV: In Vivo Evaluation of the Rechargeable Glucose Sensor

Abstract

A glucose monitoring system consisting of a pair of amperometric sensors: a glucose biosensor based on oxygen electrode and an oxygen sensor, two miniature potentiostats, an instrumentation amplifier and a data logger has been developed. The glucose sensor has linear response to the glucose concentration in vitro at 37°C up to 26 mM (480 mg/dL) in the phosphate buffer solution (pH 7.4), and linear range up to 21 mM (380 mg/dL) in undiluted bovine plasma. The system was evaluated in vivo with the sensors subcutaneously implanted in healthy mongrel dogs. During the implantation the system output was continuously recorded. The results of short-term subcutaneous implantation of the integrated system demonstrated good agreement between the glucose concentration measured by the biosensor and that obtained using standard glucose determination methods. The delay-time between the tissue glucose level (measured by the biosensor) and the blood glucose level (obtained by standard methodology) was 3 to 10 minutes. During the chronic implantation the biosensor was refilled in vivo. Rejuvenation of the sensor response after refilling was observed demonstrating the potential of such sensors for long-term implantation.