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.     

Novel Potentiometric Sensors for Determination of Melatonin and Oxomemazine in Biological Samples and in Pharmaceutical Formulations

Simple, selective and accurate sensors were developed for the determination of melatonin and oxomemazine in biological samples (urine) and in pharmaceutical preparations. Potentiometric measurements were based on bismus tetraiodate‐drug ion‐pair as novel electroactive materials incorporating a plasticized PVC membrane with o‐nitrophenyl octyl ether or dioctyl phthalate. Each sensor was conditioned for at least two days in 0.1 M drug solution before use. It exhibited fast and stable Nernstian response for melatonin and oxomemazine over the concentration range of 1.0×10^?6–1.0×10^?2 M and 1.0×10^?5–1.0×10^?2 M, pH range of 3.0–6.5 and 3.5–6.0 for melatonin and oxomemazine sensors, respectively. Results with an average recovery not more than 101 % and a mean standard deviation less than 1.0 % of the nominal were obtained for the four sensors. The sensors showed reasonable selectivity towards investigated drugs in presence of many cations.     

Nickel Pyrazolyl Borate Complex: Synthesis,Structure, and Analytical Application as Benzoate Selective Sensor

The complex [Tp^Ph,MeNi(Cl)Pz^Ph,MeH] ( I ) [Tp^Ph,Me=hydrotris(3‐phenyl‐5‐methyl‐pyrazol‐1‐yl)borate; Pz^Ph,MeH=3‐phenyl‐5‐methyl‐pyrazole] has been synthesized and explored as ionophore for the preparation of a poly(vinyl chloride) (PVC) membrane sensor for benzoate anions. The formation constants for the interaction of complex I with different organic/inorganic anions in solution have also been studied by sandwich membrane method. PVC based membranes of I using tridodecylmethylammonium chloride (TDDMACl) as cation discriminator and o‐nitrophenyloctyl ether (o‐NPOE), dibutylphthalate (DBP), benzylacetate (BA) and tributylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as benzoate selective sensors. The best performance was shown by the membrane with composition (w/w) of I (5): PVC (150): NPOE (345): TDDMACl (0.3). The proposed sensor exhibits significantly enhanced selectivity toward benzoate ions over the concentration range 2.2×10^?6–1.0×10^?1 M with a lower detection limit of 1.4×10^?6 M and a Nernstian slope of 59.2 mVdecade^?1 of activity within a pH range of 4.5–8.5. The sensor has a response time of 12 s and can be used for at least 8 weeks without any considerable divergence in their potential response. The membrane sensor of complex I have been checked for reversible and accurate sensing of benzoate levels present in liquid food products.     

Novel Ytterbium(III) Selective Membrane Sensor Based on N‐(2‐Pyridyl)‐N′‐(2‐Methoxyphenyl)‐Thiourea as an Excellent Carrier and Its Application to Determination of Fluoride in Mouth Wash Preparation Samples

The construction, performance, and applications of a novel ytterbium(III) sensor based on N‐(2‐pyridyl)‐N′‐(2‐methoxyphenyl)‐thiourea (PMT), as an excellent carrier, in plasticized poly(vinyl chloride) PVC matrix, is described. The influences of membrane composition and pH on the potentiometric response of the sensor were investigated. The sensor exhibits a nice Nernstian response for Yb(III) ion over a wide concentration range of 4 decades of concentration (1.0×10^?6–1.0×10^?2 M), and a detection limit of 5.0×10^?7 M. The response time of the electrodes is between 8 and 10 s, depending on the concentration of ytterbium(III) ions. The proposed sensor can be used for about 8 weeks without any considerable divergence in potential. The sensor revealed very good selectivity for Yb(III) in the presence of several metal ions. The best performance was observed for the membrane containing; 30% PVC, 59% o‐nitrophenyloctyl ether (NPOE) as solvent mediator, 7% PMT, and 4% sodium tetraphenyl borate (NaTPB). It was successfully applied as indicator electrodes in the potentiometric titration of Yb(III) with EDTA and for the determination of fluoride ion in two mouth wash formulations. The proposed La(III) sensor was found to work well under laboratory conditions. It was also used as an indicator electrode in titration of a 1.0×10^?4 M of Yb(III) with a standard EDTA solution (1.0×10^?2 M). It was also used for determination of Yb(III) ion in Xenotime .     

Construction of a Highly Selective and Sensitive La(III) Sensor Based on N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea for Nano Level Monitoring of La(III) Ions

N‐(2‐Pyridyl)‐N′‐(4‐methoxyphenyl)‐thiourea (PMPT) was found to be a suitable neutral ion carrier for the construction of a highly selective and sensitive La(III) membrane sensor. Poly(vinyl chloride) (PVC) based membranes of PMPT with potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) as an anionic excluder and oleic acid (OA), dibutyl phthalate (DBP), benzyl acetate (BA) and o‐nitrophenyloctyl ether (NPOE) as plasticizing solvent mediators were constructed and investigated as La(III) membrane sensors. A membrane composed of PMPT‐PVC‐KTpClPB‐BA with the ratio 8.0 : 35.0 : 3.0 : 54.0 works well over a very wide concentration range (4.0×10^?8 to 1.0×10^?1 M) with a Nernstian slope of 19.6±0.2 mV per decade of activity between pH values of 4.0 and 9.0. The detection limit of the sensor was calculated to be 2.0×10^?8 M (ca. 3.0 ppb). The sensor displays very good discrimination toward La(III) ions with regard to most common metal ions and lanthanide ions. The proposed sensor shows a short response time for whole concentration range (ca. 12 s). For evaluation of the analytical applicability of the La(III) sensor, it was successfully used as an indicator electrode for the titration of La(III) ions with EDTA. It was also applied to the determination of fluoride content of two mouth wash preparation samples and monitoring of La(III) ions in some binary and ternary mixtures.     

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.     

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。     

A New Validated Potentiometric Method for Batch and Continuous Quality Control Monitoring of Oseltamivir Phosphate (Taminil) in Drug Formulations and Biological Fluids

A new validated potentiometric method is described for batch and continuous quality control monitoring of the drug oseltamivir phosphate (Taminil) (OST). The method involves the development of a potentiometric sensor responsive to the drug based on the use of the ion‐association complex of (OST⁺) cation with phosphomolybdate anion (PMA^?) as an electroactive material in a poly(vinyl chloride) matrix membrane plasticized with o‐nitrophenyloctyl ether (o‐NPOE). Optimization of the performance characteristics of the sensor is described. A membrane incorporating the OST‐PMA‐NPOE complex in a tubular flow through detector is used in a two channel flow injection set up for continuous monitoring of the drug at a frequency of ～30 samples h^?1. The sensor shows fast near‐Nernstian response for OST over the concentration range 5.2×10^?5–0.8×10^?2 M (21.34 µg mL^?1–3.23 mg mL^?1) with a detection limit of 9.1×10^?6 M (3.73 µg mL^?1) over the pH range 4.6–6.1. The sensor displays good selectivity for OST drug over some basic drugs, inorganic cations, excipients and diluents commonly used in the drug formulations. Validation of the assay method is tested by measuring the lower detection limit, range, linearity, bias, trueness, accuracy, precision, and between‐day‐variability, within day reproducibility, selectivity and ruggedness (robustness). The results reveal good potentiometric performance of the proposed sensor for determination of OST in pharmaceutical capsules and in biological fluid matrices as well as for testing the dissolution profile of the drug and drug homogeneity.     

Novel Biomedical Sensors for Flow Injection Potentiometric Determination of Creatinine in Human Serum

Coated‐wire (CW) and tubular (Tu) type membrane sensors for creatinine are developed. These consist of creatinine tungstophosphate(CTP), creatinine molybdophosphate (CMP) and creatinine picrolonate (CPC) ion‐pair complexes as electroactive materials dispersed in plasticized poly(vinyl chloride) matrix membranes. Electrochemical evaluation of these sensors under static (batch) mode of operation reveals near‐Nernstian response with slopes of 62.9, 58.1, and 55.2 mV decade^?1 over the concentration range 1×10^?2–5.0×10^?6, 1×10^?2–7.5×10^?5, and 1×10^?2?3.1×10^?5 mol L^?1. The lower detection limits are 0.39, 3.49, and 2.20 μg mL^?1 creatinine with CTP, CMP and CPC membrane based sensors plasticized with o‐NPOE, respectively. Tubular and coated wire CTP membrane sensors are incorporated in flow‐through cells and used as detectors for flow injection analysis (FIA) of creatinine. The intrinsic characteristics of the detectors under hydrodynamic mode of operation in a low dispersion manifold are determined and compared with data obtained under static mode of operation. With 10^?2 mol L^?1 phosphate buffer of pH 4.5 as a carrier solution, the tubular and coated wire CTP detectors exhibit rapid response of 58.9 and 50.7 mV decade^?1 over the concentration range 1×10^?2–1×10^?5 mol L^?1 and detection limits of 0.39 μg mL^?1 and 0.85 μg mL^?1, respectively. Validation of the assay methods with the proposed sensors by measuring the lower detection limit, range, accuracy, precision, repeatability and between‐day‐variability reveals good performance characteristics confirming applicability for continuous determination of creatinine. The sensors are used for determining creatinine in human blood serum at an input rate of 40 samples per hour. No interferences are caused by creatine, most common anions, cations and organic species normally present in biological fluids. The results favorably compare with data obtained using the standard spectrophotometric method.     

Development of a Novel Automatic Potentiometric System for Determination of Selenium and Its Application in Pharmaceutical Formulations and Anodic Slime

Poly(vinyl chloride) polymeric membrane sensors containing Sn(IV) phthalocyanine dichloride (SnPC) and Co(II) phthalocyanine (CoPC) as novel electroactive materials dispersed in o‐nitrophenyl octylether (o‐NPOE) as a plasticizer are examined potentiometrically with respect to their response toward selenite (SeO₃^2?) ions. Fast Nernstian response for SeO₃^2? ions over the concentration ranges 7.0×10^?6–1.0×10^?3 and 8.0×10^?6–1.0×10^?3 mol L^?l at pH 3.5–8.5 with lower detection limit of 5.0×10^?6 and 8.0×10^?6 mol L^?1 and calibration slopes of ?25.4 and ?29.7 mV decade^?1 are obtained with SnPC and CoPC based membrane sensors, respectively. The proposed sensors reveals by the modified separate solution method (MSSM) a good selectivity over different anions which differ significantly from the classical Hofmeister series. A segmented sandwich membrane method is used to determine complex formation constants of the ionophores in situe in the solvent polymeric sensing membranes. Membrane incorporating CoPC in a tubular flow detector is used in a two channels flow injection set up for continuous monitoring of selenite at a frequency of ca. 50 samples h^?1. Direct determination of selenium in pharmaceutical formulations and anodic slime gives results in good agreement with data obtained using standard ICP method.     

A Highly Selective and Sensitive Barium(II)‐Selective PVC Membrane Based on Dimethyl 1‐Acetyl‐8‐oxo‐2,8‐dihydro‐ 1H‐pyra‐zolo[5,1‐a]isoindole‐2,3‐dicarboxylate

A poly(vinyl chloride)‐based membrane of dimethyl 1‐acetyl‐8‐oxo‐2,8‐dihydro‐1H‐pyra‐zolo[5,1‐a]isoindole‐2,3‐dicarboxylate as a neutral carrier with sodium tetraphenylborate (NaTPB) as an anion excluder and 2‐nitrophenyl octyl ether (NPOE) as plasticizer was prepared and investigated as a Ba(II)‐selective electrode. The electrode exhibits a Nernstian slope of 29.7±0.4 mV per decade over a wide concentration range (1.0×10^?6 to 1.0×10^?1 M) with a detection limit of 7.6×10^?7 M between pH 3.0 and 11.0. The response time of the sensor is about 10 s and it can be used over a period of 2 months without any divergence in potential. The proposed membrane sensor revealed good selectivity for Ba(II) over a wide variety of other metal ions. It was successfully used in direct determination of barium ions in industrial wastewater samples.     

A Novel Holmium(III) Membrane Sensor Based on N‐(1‐Thien‐2‐Ylmethylene)‐1,3‐Benzothiazol‐2‐Amine

Abstract

A novel plasticized membrane sensor for Ho(III) ions based on N‐(1‐thien‐2‐ylmethylene)‐1,3‐benzothiazol‐2‐amine (TBA) as a neutral carrier was prepared. The best performance was obtained with a membrane composition of 31% PVC, 61% benzyle acetate, 2% sodium tetra phenyl borate and 6% carrier. The electrode exhibits a Nernstian response for Ho(III) ions over a particular concentration range (1.0×10^?5?1.0×10^?2 M) with a slope of 19.7±0.2 mV decade^?1. The limit of the detection is 7.0×10^?6 M. The sensor has a response time of <15 s and a useful working pH range of 4.0–9.5. The proposed sensor discriminates relatively well towards Ho(III) ions with regard to common alkali, alkaline earth, and specially lanthanide ions. It was successfully applied as an indicator electrode in a potentiometric titration of Ho(III) ions with EDTA. It was also applied in determination of fluoride ions in a mouth wash preparation. The proposed sensor was applied for the determination of Ho(III) ion concentration in binary mixtures.     

An Asymetric Lutetium(III) Microsensor Based on N‐(2‐Furylmethylene) Pyridine‐2,6‐Diamine for Determination of Lutetium(III) Ions

Abstract

In this work, for the first time, we introduce a highly selective and sensitive lutetium(III) micro‐sensor. N‐(2‐furylmethylene) pyridine‐2,6‐diamine (FPD) was used as a membrane‐active component to prepare a highly sensitive Lu(III)‐selective polymeric membrane microelectrode. Theoretical calculations for FPD, lutetium and some other metal ions were carried out and selectivity toward Lu(III) ions was confirmed. The best performance was achieved by a membrane composed of 32% PVC, 60% o‐nitrophenyloctyl ether, 4% potassium tetrakis (p‐chlorophenyl) borate (KTpClPB) and 4% FPD. The electrode exhibits a Nernstian response for Lu(III) ions over a particular concentration range (1.0×l0^?11?1.0×10^?6 mol l^?1) with a slope of 20.5±0.2 mV decade^?1. The detection limit is 3.0×10^?11 mol l^?1 while the sensor presents a response time of <10 s and a useful working pH range of 4.0–10.5. As a matter of fact, the proposed sensor discriminates relatively well for Lu(III) ions in compare to common alkali, alkaline earth, heavy metals and, specially, lanthanide ions. The sensor was successfully applied as an indicator electrode in a potentiometric titration of Lu(III) ions with EDTA. In addition, it was used for determination of lutetium in some soil samples where domestic devices were stored. The proposed sensor was evaluated for Lu(III) ions determination in some binary mixtures.     

Novel Polymeric Membrane Sensors Based on Mn(III) Porphyrin and Co(II) Phthalocyanine Ionophores for Batch and Flow Injection Determination of Azide

Two novel potentiometric azide membrane sensors based on the use of manganese(III)porphyrin [Mn(III)P] and cobalt(II)phthalocyanine [Co(II)Pc] ionophores dispersed in plasticized poly(vinyl chloride) PVC matrix membranes are described. Under batch mode of operation, [Mn(III)P] and [Co(II)Pc] based membrane sensors display near‐ and sub‐Nernstian responses of ?56.3 and ?48.5 mV decade^?1 over the concentration ranges 1.0×10^?2?2.2×10^?5 and 1.0×10^?2?5.1×10^?5 mol L^?1 azide and detection limits of 1.5×10^?5 and 2.5×10^?5 mol L^?1, respectively. Incorporation of both membrane sensors in flow‐through tubular cell offers sensitive detectors for flow injection (FIA) determination of azide. The intrinsic characteristics of the [Mn(III)P] and [Co(II)Pc] based detectors in a low dispersion manifold show calibration slopes of ?51.2 and ?33.5 mV decade^?1 for the concentration ranges of 1.0×10^?5?1.0×10^?2 and 1.0×10^?4?1.0×10^?2 mol L^?1 azide and the detection limits are1.0×10^?5 and 3.1×10^?5 mol L^?1, respectively. The detectors are used for determining azide at an input rate of 40–60 samples per hour. The responses of the sensors are stable within ±0.9 mV for at least 8 weeks and are pH independent in the range of 3.9?6.5. No interferences are caused by most common anions normally associated with azide ion.     

Flow‐Through Potentiometric Sensors for Alizarin Red S Dye and Their Application for Aluminum Determination

Novel selective and sensitive poly (vinyl chloride) membrane sensors are developed for measuring alizarin red S (AR) based on the use of aliquate 336, Mg^IIphthalocyanine (MgPc), Cu^IIphthalocyanine (CuPc) and Fe^II phthalocyanine (FePc) plasticized poly (vinyl chloride) membrane. The sensors display Nernestian response with slopes of ‐50.6 ± 0.6 , ‐37.4 ± 0.5 , ‐37.7 ± 0.8 and ‐35.0 ± 0.7 mV decade^?1 over the range of 5.2 × 10^?6 to 1 × 10^?2 mol L^?1 for all of them and detection limits of 5.9 × 10^?7, 1.9 × 10‐^?6 2.3 × 10^?6 and 1.9 × 10^?6 mol L^?1 for aliquate, MgPc, CuPc and FePc membrane based sensor, respectively. The sensors exhibit long life span, long term potential stability, high reproducibility, fast response and good discrimination ability towards alizarinate ion in comparison with many other anions. A tubular detector based on aliquate, MgPc, CuPc and FePc was further developed and coupled to a flow‐injection system for alizarin (AR) determination. Under optimized conditions, the linearity range is 1.0 × 10^?5‐ 1.0 × 10^?1 mol L^?1, with a slope of ‐52.1 ± 0.8, 20.9 ± 0.7, 23.6 ± 0.4 and 25 ± 1.1 mV decade^?1 and a reproducibility of ± 0.8 mV (n = 6) for aliquate, MgPc, CuPc and FePc membrane based sensors, respectively. The sensor based on aliquate is further utilized for a potentiodynamic quantification of aluminum in sludge samples and deodorants. The buffered solution of alizarin was allowed to react in a flow system with aluminum. The calibration curve of Al was found to be linear over a concentration range of 0.1 to 1.8 and 1.0 ‐ 40 μg mL^?1 with a slope = 16.9 (r² = 0.993) and 1.76 (r² = 0.994) mV (μg/mL)^?1 and a detection limit of 0.08 and 0.5 μg mL^?1 for 10^?4 and 10^?3 mol L^?1 AR^? as a carrier, respectively. The method was successfully used for determining aluminum in sludge samples and deodorants. The data agree fairly well the nominal values and with results obtain by continuous flow hydride generation inductively coupled plasma (ICP) method.     

A Novel Flow‐Through Planar Solid Contact Sensor for the Determination of Lead with Potentiometric Anionic Response

The construction and general performance characteristics of two poly(vinyl chloride) matrix chemical sensors for lead were described. These sensors were based on the use of ion association complexes of trihydroxoplumbate, [Pb(OH)₃]^? and tetraiodoplumbate, [PbI₄]^2?with cetylpyridinium chloride (CP) and iron(II)‐4,7‐bathophenanthroline [Fe(bphen)₃]²⁺ as novel electroactive materials dispersed in o‐nitrophenyloctyl ether (o‐NPOE) plasticizer for ionometric sensor controls, respectively. The sensing membrane (3×5 mm) is immobilized on a wafer polyimide chip (size 13.5×3.5 mm) to offer a planar miniaturized design that could be easily used flow injection system. Under static modes of operation, the sensors revealed a near Nernstian response over a wide Pb²⁺ ion concentration range 7.9×10^?7 to 10^?4 and 3.2×10^?7 to 10^?4 mol L^?1 with detection limit of 100 and 45.5 ng mL^?1, respectively . In flow injection potentiometry, excellent reproducibility (RSD%=0.5%), fast response, high sensitivity, high sampling rate (50 sample h^?1) and stable baseline was observed in the presence of 5×10^?2 mol L^?1 NaOH and 10^?1 mol L^?1 KI as a carrier for [CP][Pb(OH)₃] and [Fe(bphen)₃][PbI₄] membrane based sensors, respectively. Validation of the assay method according to the quality assurance standards (range, within‐day repeatability, between‐day variability, standard deviation, accuracy, lower detection limit) reveals good performance characteristics and suggests application for routine determination of lead in industrial wastewaters and stack emissions of lead smelters. The results agree fairly well with data obtained by the standard atomic absorption methods.     

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.     

All Solid State Chromium(III) Selective Potentiometric Sensor Based on 2‐(1‐(2‐((3‐(2‐Hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol

Highly selective all solid state electrochemical sensor based on a synthesized compound i.e. 2‐(1‐(2‐((3‐(2‐hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol (I) as an ionophore has been prepared and investigated for the selective quantification of chromium(III) ions. The effect of various plasticizers, viz. dibutyl phosphonate (DBP), dibutyl(butyl) phosphonate (DBBP), nitrophenyl octyl ether (NPOE), tris‐(2‐ethylhexyl)phosphonate (TEP), tri‐butyl phosphonate (TBP), dioctyl phthalate (DOP), dioctyl sebacate (DOS), benzyl acetate (BA) and acetophenone (AP) along with anion excluders NaTPB (sodium tetraphenyl borate) and KClTPB (potassium(tetrakis‐4‐chlorophenyl)borate was also studied. The optimum composition of the best performing membrane contained (I):KClTPB:NPOE:PVC in the ratio 15 : 3 : 40 : 42 w/w. The sensor exhibited near Nernstian slope of 20.1±0.2 mV/decade of activity in the working concentration range of 1.2×10^?7–1.0×10^?1 M, and in a pH range of 3.8–4.5. The sensor exhibited a fast response time of 10 s and could be used for about 5 months without any considerable divergence in potentials. The proposed sensor showed very good selectivity over most of the common cations including Na⁺, Li⁺, K⁺, Cu²⁺, Sr²⁺, Ni²⁺, Co²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Zn²⁺, Cs⁺, Mg²⁺, Cd²⁺, Al³⁺, Fe³⁺and La³⁺. The activity of Cr(III) ions was successfully determined in the industrial waste samples by using this sensor.     

Potentiometric sensor for the nanoscale monitoring of Ni2+ ion in environmental samples by the fabrication of coated pyrolytic graphite electrode based on a novel C–C-coupled compound

Novel ligand 5,5?-((3-nitrophenyl)methylene)bis(2,6-diaminopyrimidin-4(3H)-one) (L) was synthesised and characterised. Preliminary studies on L have showed that it has more affinity towards the Ni²⁺ ion. Thus, the L was used as the electroactive material in the fabrication of poly(vinyl chloride) (PVC)-based membrane sensors such as coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE). Several polymeric membranes were fabricated by incorporating L as ionophore, NaTPB as anion excluders and BA, 1-CN, DBP, DOP and o-NPOE as solvent mediators and their effect on potentiometric response studied. Comparative electroanalytical studies performed on the CGE and CPGE depict that the CPGE with optimised membrane composition of L:PVC:o-NPOE:NaTPB in the ratio of 7:33:58:2 (w/w, mg) exhibited the best response in terms of wide working concentration range from 2.0 × 10^?8 to 1.0 × 10^?1 mol L^?1, (3.64 µg L^?1 –18.2 g L^?1) lower detection limit of 8.1 × 10^–9 mol L^?1 (1.47 µg L^?1) with Nernstian compliance of 29.4 ± 0.2 mV decade^?1 of activity of Ni²⁺ ion in the pH range of 3.5–9.0. The sensor can work satisfactorily in water–acetonitrile and water–methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor showed fast response time of 8 s and could be used successfully for a period of 4 months. The sensor reflects its utility in the quantification of Ni²⁺ ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Ni²⁺ ion with EDTA.     

A Novel Potentiometric Membrane Sensor Based on Aryl Palladium Complex for Selective Determination of Thiocyanate in the Saliva and Urine of Cigarette Smokers

A highly selective potentiometric sensor for thiocyanate ion based on the use of a newly synthesized organo‐palladium ion exchanger complex dispersed in a plasticized poly(vinyl chloride) membrane is described. The sensor displays a Nernstian response (?57.8±0.2 mV decade^?1) over a wide linear concentration range of thiocyanate (1.0×10^?6–1.0×10^?1 mol L^?1 ), low detection limit (6.3×10^?7 mol L^?1), fast response (20 s), stable potential readings (±0.4 mV), good reproducibility (±0.9%), long term stability (8 weeks), high precision (±0.7%) and applicability over a wide pH range (4–10). Negligible interferences are caused by F^?, Cl^?, I^?, Br^?, NO₃^?, NO₂^?, CN^?, SO₄^2?, S₂O₃^2?, PO₄^3?, citrate, acetate and oxalate ions. Under hydrodynamic mode of operation (FIA), the calibration slope is ?51.1±0.1 mV decade^?1, the linear response range is 1.0×10^?5–1.0×10^?1 mol L^?1 SCN^? and the sample throughput is 40–45 per hour. The sensor is satisfactory used for manual and flow injection potentiometric determination of SCN^? in the saliva and urine of cigarette smokers and non smokers. The data agree fairly well with results obtained by the standard spectrophotometric technique. Direct potentiometry and potentiometric titration of SCN^? with Ag⁺ are also monitored with the sensor.