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.     

Thiocyanate-selective membrane electrode based on cobalt(III) Schiff base as a charge carrier

A highly selective polyvinylchloride (PVC) membrane electrode based on Schiff base complex i.e. [Cobalt (Salpen) (PBu₃)] ClO4 · H2O (Salpen = bis(salycilaldehyde)propylene diamine) is reported as new carrier for thiocyanate selective electrode by incorporating the membrane ingredients on the surface of graphite electrodes. The proposed electrode possesses a very wide Nernestian linear range to thiocyanate from 1.0 × 10^?6 to 1.0 × 10^?1 M with slope of ?59.05 ± 0.91 mV per decade of thiocyanate concentration, very low detection limit (8.0 × 10^?7 M) and good thiocyanate selectivity over the wide variety of other anions. Fast and stable response, good reproducibility, long-term stability, applicability over a wide pH range (2.8–9.8) are advantages of the reported electrode. The sensor has a response time of <5 s and can be used for at least 14 weeks without any considerable change in respective potential response. The proposed electrode was used for the determination of thiocyanate in saliva, wastewater and human urine with satisfactory results and good agreement with colorimetric as reference method.     

Highly selective PVC-membrane electrodes based on Co(II)-Salen for determination of nitrite ion.

A cobalt(II) derivative was used as a suitable ionophore for the preparation of a polymeric membrane nitrite-selective electrode. The electrode reveals a Nemstian behavior over a very wide NO2- ion concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) and a very low detection limit (5.0 x 10(-7) M). The potentiometric response is independent of the pH of solution in the pH range 4.0-9.5. The electrode shows advantages such as low resistance, fast response and, most importantly, good selectivity relative to a wide variety of inorganic and organic anions. In fact, the selectivity behavior of the proposed NO2- ion-selective electrode shows great improvements compared to the previously reported electrodes for nitrite ion. The proposed electrodes could be used for at least 2 months without any significant changes in potentials. The electrode was successfully applied to the determination of nitrate ion concentrations in sausage and milk samples.     

Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate

A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets.     

Charge-transfer triiodide ion-selective electrode based on 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane.

A new PVC membrane electrode for the triiodide ion based on a charge-transfer complex of iodine with 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane as a membrane carrier was prepared. The electrode exhibits a Nernstian response for triiodide ions over a wide concentration range (1.0 x 10(-1)-1.0 x 10(-5) M) with a slope of 59.3 +/- 0.9 mV decade(-1) and a detection limit of 6.3 x 10(-6) M. It has a response time of 30 s and can be used for at least 3 months without any divergence in the potential. The potentiometric response is independent of the pH, in the pH range 1.6 - 10.0. The proposed electrode has shown very high selectivity for the triiodide ion over a wide variety of other anions. This electrode was successfully applied as an indicator electrode in the potentiometric titration of ascorbic acid and hydroquinone from pharmaceutical preparations as well as ascorbic acid in orange juice and dissolved O2 in tap water.     

Highly selective thiocyanate membrane electrode based on butane-2,3-dione bis(salicylhydrazonato)zinc(II) complex

A highly selective poly(vinyl chloride) (PVC) membrane electrode based on butane -2,3-dione bis(salicylhydrazonato) zinc(II) [Zn (BDSH)] complex as carrier for thiocyanate-selective electrode is reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The sensor responds to thiocyanate in linear range from 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope −56.5 ± 1.1 mV decade⁻¹, over a wide pH range of 3.5-8.5. The limit of detection of the electrode was 7.0 × 10⁻⁷ M SCN⁻. Selectivity coefficients determined with fixed interference method (FIM) indicate a good discriminating ability towards SCN⁻ ion in comparison to other anions. The proposed sensor has a fast response time of about 5-15 s and can be used for at least 3 months without any considerable divergence in potential. It was applied as indicator electrode in titration of thiocyanate with Ag⁺ and in potentiometric determination of thiocyanate in saliva and urine samples.     

Thiocyanate-selective electrode based on unsymmetrical benzoN(4) nickel(II) macrocyclic complexes

Unsymmetrical benzoN(4) nickel(II) macrocyclic complexes have been explored as an ionophore for preparing PVC-based membrane electrodes selective to SCN(-). The resulting electrode exhibited the best working concentration range (1.4x10(-7)-0.1 M) with a Nernstian slope of (-59.7+/-0.9 mV per decade) in the wide pH range of 3.5-10.5. The proposed electrode has a very fast response time (5 s) and high selectivity for thiocyanate over variety of anions. This sensor was successfully applied as an indicator electrode to potentiometric titration of thiocyanate ion with AgNO(3) and for direct determination of the amount of thiocyanate in urine and saliva samples in order to distinguish between smokers and nonsmokers.     

Highly selective and sensitive thiocyanate membrane electrode based on nickel(II)-1,4,8,11,15,18,22,25-octabutoxyphthalocyanine

A highly selective membrane electrode based on nickel(II)-1,4,8,11,15,18,22,25-octabutoxyphthalocyanine (NOBP) is presented. The proposed electrode shows very good selectivity for thiocyanate ions over a wide variety of common inorganic and organic anions. The sensor displays a near Nernstian slope of −58.7 ± 0.6 mV per decade. The working concentration range of the electrode is 1.0 × 10⁻⁶ to −1.0 × 10⁻¹ M with a detection limit of 5.7 × 10⁻⁷ M (33.06 ng/mL). The response time of the sensor in whole concentration ranges is very short (<10 s). The response of the sensor is independent on the pH range of 4.3-9.8. The best performance was obtained with a membrane composition of 30% PVC, 65% dibutyl phthalate, 3% NOBP and 2% hexadecyltrimethylammonium bromide. It was successfully applied to direct determination of thiocyanate in biological samples, and as an indicator electrode for titration of thiocyanate ions with AgNO₃ solution.     

Highly selective iodide membrane electrode based on a cerium salen.

A highly selective PVC membrane electrode based on a cerium-salen complex was prepared. The sensor displays an anti-Hofmeister selectivity sequence with a preference for iodide ion over many common organic and inorganic anions. The proposed electrode exhibits a near-Nernstian behavior over a wide concentration range (5.0 x 10(-2) - 8.0 x 10(-6) M) with a slope of 57.5 mV per decade, and a detection limit of 6.0 x 10(-6) M. The electrode has a very fast response time and can be used in the pH range of 3.0 - 1 1.0. It was applied, as an indicator electrode, in potentiometric titration of Ag+ ions.     

Liquid-membrane electrode sensitive to ammonia and aliphatic amines based on 1-[(2-oxyphenyl)iminomethly]-2-oxybenzene-O,O',N-ammin-nickel(II) complex

In this study, an ammonia-gas-sensing liquid-state membrane electrode based on 1-[(2-oxyphenyl)iminomethyl]-2-oxybenzene-O,O',N-ammin-nickel(II) (Ni(II)-Schiff base) as an ionophore was developed. This membrane electrode gave a very good performance and exhibited linear response with near-Nernstian slope of 50.7+/-0.5 mV per decade, within a concentration range of 1.0x10(-1)-1.0x10(-3) M. The electrode performance depends on the pH of the test solution and the optimum pH range was 10.0-11.5. The effect of concentration of internal solutions in the electrode was also investigated. The selectivity properties of the electrode towards aliphatic amines at a pH value of 10.2 were investigated with the mixed-solution method. Furthermore, the response time and lifetime of the electrode prepared were determined.     

Synthesis of N'-(1-pyridin-2-ylmethylene)-2-furohydrazide and its application in construction of a highly selective PVC-based membrane sensor for La(III) ions.

A highly La(III) ion-selective PVC membrane sensor based on N'-(1-pyridin-2-ylmethylene)-2-furohydrazide (NPYFH) as an excellent sensing material was successfully developed. The electrode shows a good selectivity for La(III) ion with respect to most common cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor exhibits a wide linear response with slope of 19.2 +/- 0.6 mV per decade over the concentration range of 1.0 x 10(-6) - 1.0 x 10(-1) M, and a detection limit of 7.0 x 10(-7) M of La(III) ions. The sensor response is independent of pH in the range of 3.5-10.0. The proposed electrode was applied as an indicator electrode in potentiometric titration of La(III) ion with EDTA.     

Thiocyanate ion selective electrode based on bis(N-3-methylphenyl salicylidenaminato)copper(Ⅱ) ionophore

In this work a PVC membrane electrode based on bis(N-3-methyl phenyl salicylidenaminato)copper(II)as ionophore was prepared.The electrode was tested by inorganic anions and showed good selectivity for thiocyanate ion.This sensor showed Nerstian behavior with a slope of a-59.3 mV per decade at 25℃.The proposed electrode exhibited a wide linear range from 1.0 × 10~(-6) mol/L to 1.0× 10~(-1) mol/L with a detection limit of 5.0×10~(-7) mol/L.The electrode response was independent of pH in the range of 4.0-10.0.The response time is about 9-21s,and the electrode can be used for over 60 days without considerable deterioration.The prepared sensor was applied as an indicator electrode in potentiometric titration of SCN with Ag~+ ion and to determine the thiocyanate in samples of urine and saliva.     

Anion selective polymeric membrane electrodes based on cyclopalladated amine complexes

The potentiometric anion selectivity of two polymer membrane based electrodes (I and II) formulated with two new cyclopalladated amine complexes as the active components are examined. The electrodes exhibit a non-Hofmeister selectivity pattern with a significantly enhanced response towards thiocyanate, iodide and nitrite. The graph potential versus log c is linear over the concentration range 10(-6)-6x10(-2) M thiocyanate with electrode I and 10(-6)-10(-3) M with electrode II; 10(-5)-10(-2) M iodide with electrode I and 10(-3)-6x10(-2) M with electrode II; and 10(-3)-6x10(-2) M nitrite with both electrodes. The influence of the plasticizer and pH are studied. The potentiometric selectivity coefficients for I, II and blank membrane electrodes are reported. The selective interaction between Pd(II) thiocyanate, iodide and nitrite is postulated to be the reason for its higher response.     

Coated wire silver-ion selective electrode based on a N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene.

A novel membrane coated platinum-wire electrode (MCPWE) based on N,N'-bis(2-thienylmethylene)-1,2-diaminobenzene (BTMD) for highly selective determination of Ag+ ion has been developed. The influences of membrane composition and pH on the potentiometric responses of electrode were investigated. The potentiometric responses are independent of the pH of the test solution in the range of 5.0 - 9.0. The electrode shows a linear response for Ag+ ion over the concentration range of 1.0 x 10(-60 to 1.0 x 10(-1) M with a lower detection limit of 6.0 x 10(-7) M. The electrode possesses a Nernstian slope of 59.7 mV decade(-1) and a fast response time of < or = 17 s and can be used for at least 2 months without any observable deviation. The proposed electrode displayed very good selectivity for Ag+ ion with respect to NH4+ and alkali, alkaline earth and some common transition metal ions. The practical utility of the electrode has been demonstrated by its use as the indicator electrode in the potentiometric titration of an AgNO3 solution with a NaI solution and in determination of the silver content of a developed radiological film.     

Determination of SCN- in urine and saliva of smokers and non-smokers by SCN(-)-selective polymeric membrane containing a nickel(II)-azamacrocycle complex coated on a graphite electrode.

The construction, performance characteristics, and application of a novel polymeric membrane coated on a graphite electrode with unique selectivity towards SCN- are reported. The electrode was prepared by incorporating Ni(II)-2,2,4,9,9,11-hexamethyltetraazacyclotetradecanediene perchlorate into a plasticized poly(vinyl chloride) membrane. The influences of membrane composition, pH and foreign ions were investigated. The electrode displays a near Nernstian slope (-57.8 mV decade-1) over a wide concentration range of 1 x 10(-7)-1 x 10(-1) M of SCN- ion. The electrode has a detection limit of 4.8 x 10(-8) M (2.8 ng/cm3) SCN- and shows response times of about 15 s and 120 s for low to high and high to low concentration sequences, respectively. The proposed sensor shows high selectivity towards SCN- over several common organic and inorganic anions. The electrode revealed a great enhancement in selectivity coefficients and detection limit for SCN-, in comparison with the previously reported electrodes. It was successfully applied to the direct determination of SCN- in milk and biological samples, and as an indicator electrode in titration of Ag+ ions with thiocyanate.     

Lead(II)-selective electrode based on phenyl disulfide.

A PVC membrane electrode for lead ions based on phenyl disulfide as the membrane carrier was developed. The electrode exhibits a good Nernstian slope of 29.3 +/- 0.7 mV/decade and a linear range of 2.0 x 10(-6)-1.0 x 10(-2) M for Pb(NO3)2. The limit of detection is 1.2 x 10(-6) M. It has a response time of 45 s and can be used for at least fifty days without any divergence in potential. The proposed membrane sensor revealed high selectivity for Pb2+ over a wide variety of other metal ions and could be used in the pH range of 3.5-6.3. The electrode was used as an indicator electrode in potentiometric titration of lead ions.     

Sulfate-selective electrode based on a complex of copper.

A new sulfate-selective electrode based on the complex N,N'-bis(2-amino-1-oxo-phenelenyl)phenylenediamine copper(II) (CuL) as the membrane carrier was developed. The electrode exhibited a good Nernstian slope of -29.5 +/- 0.5 mV/decade and a linear range of 1.0 x 10(-7) - 1.0 x 10(-1) M for sulfate. The limit of detection was 1.0 x 10(-8) M. It has a fast response time of 10 s and can be used for more than three months. The selective coefficients were determined by the fixed interference method (FIM). The electrode could be used in the pH range 3.5 - 8.0. It was employed as an indicator electrode for direct determination of sulfate in pharmacy and cement samples.     

Aluminium(III)-selective electrode based on a newly synthesized tetradentate Schiff base

A PVC membrane electrode for aluminium ion based on bis(5-phenyl azo salicylaldehyde) 2,3-naphthalene diimine (5PHAZOSALNPHN) as an ion carrier was developed. The electrode exhibits a Nernstian slope of 19.3+/-0.8 mV per decade and a linear range of 5.0x10(-6)-1.0x10(-2) M for Al(NO(3))(3). The limit of detection is 2.5x10(-6) M. It has a fast response time of about 10 s and can be used for at least 10 weeks without observing any deviation. The proposed membrane sensor revealed good selectivity for Al(3+) over a wide variety of other metal ions and could be used in pH range of 2.9-5.0. It was used as an indicator electrode in potentiometric titration of aluminium ion.     

Fabrication of PVC based membrane using nickel porphyrazine as ionophore in the screening of thiocyanate ion in aqueous and real samples

The [Ni[(TAP)(SBn)8]] complex (I), i.e. ([2,3,7,8,12,13,17,18-octakis(benzylthio)-5,10,15,20-tetraazaporphyrin])nickel(II), has been explored as an ionophore for fabrication of the PVC based membrane electrodes used in the screening of thiocyanate anion (SCN-). The membrane having [Ni[(TAP)(SBn)8]] complex (I) as an electroactive material and dioctylphthalate (DOP) as plasticizer in the PVC matrix with the percentage ratio 5 : 158 : 200 (I : DOP : PVC, % w/w) exhibited a linear response in the concentration range 7.0 x 10(-6)-1.0 x 10(-1) M of SCN- with a sub-Nernstian slope 32.5 +/- 0.2 mV/decade of activity and a fast response time of 10 +/- 2 s. The sensor works well in the pH range 3.0 - 9.5 and could be satisfactorily used in presence of 50 % (v/v) methanol, ethanol and acetone, and is selective for SCN- over a large number of anions with slight interference from iodide (I-) and azide (N3-) if present at a level >or = 1.0 x 10(-5) M. Described electrode works well over a period of six months. The sensor can be successfully applied for the screening of SCN- in both aqueous and real samples and also as indicator electrodes in precipitation titrations.     

Selective thiocyanate poly(vinyl chloride) membrane based on a 1,8-dibenzyl-1,3,6,8,10,13-hexaazacyclotetradecane-Ni(II) perchlorate

A highly selective poly(vinyl chloride) (PVC) membrane electrode based on 1,8-dibenzyl-1,3,6,8,10,13-hexaazacyclotetradecane-Ni(II) as a membrane carrier with unique selectivity toward thiocyanate is reported. The influence of membrane composition, pH and foreign anions were investigated. The sensor exhibits a Nernstian response for thiocyanate over a wide concentration range of 3.3×10⁻⁶ to 0.10 M, with a slope 58.4±0.3 mV per decade. The limit of detection is 3.0×10⁻⁶ M SCN⁻. The sensor has a response time of <20 s and can be used for at least 2 months without any considerable divergence in potential. The proposed electrode shows fairly a good discriminating ability towards SCN⁻ ion in comparison to other anions. It was successfully applied to direct determination of thiocyanate in urine and saliva and it was also used as an indicator electrode in titration of thiocyanate with Ag⁺ ions.