Co2+-selective membrane electrode based on the Schiff Base NADS

A new PVC membrane electrode for cobalt(II) ions based on a recently synthesized Schiff base of 5-((4-nitrophenyl)azo)- N-(2',4'-dimethoxyphenyl)salicylaldimine is reported. The electrode exhibits a Nernstian response for Co(2+) ions over a wide concentration range (9.0 x 10(-7)-1.0 x 10(-2) M) with a slope of 29(+/-1). The limit of detection is 8.0 x 10(-7) M. The proposed sensor revealed good selectivities over a wide variety of other cations including hard and soft metals. This electrode could be used in a pH range of 3.5-6.0. It was used as an indicator electrode in potentiometric titrations of cobalt(II) ions and can be used in the direct determination of Co(2+) in aqueous solutions.     

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.     

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.     

Cobalt(II)-selective membrane electrode based on a recently synthesized benzo-substituted macrocyclic diamide.

A PVC-membrane electrode based on a recently synthesized 18-membered macrocyclic diamide is presented. The electrode reveals a Nernstian potentiometric response for Co2+ over a wide concentration range (2.0 x 10(-6)-1.0 x 10(-2) M). The electrode has a response time of about 10 s and can be used for at least 2 months without any divergence. The proposed sensor revealed very good selectivities for Co2+ over a wide variety of other metal ions, and could be used over a wide pH range (3.0-8.0). The detection limit of the sensor is 6.0 x 10(-7) M. It was successfully applied to the direct determination and potentiometric titration of cobalt ion.     

A polystyrene based membrane electrode for cadmium(II) ions

A polystyrene based membrane of 3,4:12,13-dibenzo-2,5,11,14-tetraoxo- 1,6,10,15-tetraazacyclooctade-cane shows a Nernstian response to Cd(II) ions over a wide concentration range (3.16 x 10(-6) - 1.00 x 10(-1) mol L(-1) with a Nernstian slope of 29.8 mV/decade of concentration, between pH 2.0 and 6.0. This electrode has been found to be chemically inert and of adequate stability with a response time of 20s. The electrode gives reproducible results with a lifetime of 130 days. The membrane works satisfactorily in a partially non-aqueous medium up to a maximum 35% (v/v) content of methanol and ethanol. The practical utility of the proposed chemical sensor has been observed by using it as end-point indicator in the titration of Cd(II) ions with EDTA. The potentiometric selectivity coefficient values indicate that the membrane sensor is highly selective for Cd(II) ions over a number of cations. Small amounts of surfactants do not disturb the functioning of the sensor. This electrode has also been used to estimate cadmium ions in real 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.     

Ribonucleic acid as a novel ionophore for potentiometric membrane sensors of some transition metal ions

Ribonucleic acid (RNA) is used as a novel ionophore in plasticized poly(vinyl chloride) matrix membrane sensors for some transition metal ions. Membranes incorporating RNA and doped in Cu(2+), Cd(2+) and Fe(2+) display fast near-Nernstian and stable responses for these ions with cationic slopes of 31.1, 31.3 and 35.5 mV per decade, respectively, over the concentration range 10(-6)-10(-2) M and pH range 4-6.5. The cadmium RNA-based sensor shows no interference by Cu(2+), Fe(2+) Hg(2+) and Ag(+), which are known to interfere significantly with the solid-state CdS/Ag(2)S membrane electrode. The copper RNA-based sensor displays general potentiometric characteristics similar to those based on macrocyclic ionophores and organic ion exchangers and has the advantage of a better selectivity for Cu(2+) over some alkaline earth, divalent and transition metal ions. The iron RNA-based membrane sensor exhibits no interference by Hg(2+) and Zn(2+), which are known to interfere with other previously suggested sensors. The nature and composition of the RNA ionophore and its cadmium complex are examined using electrophoresis, Fourier-transform infrared analysis, elemental analysis and X-ray fluorescence techniques.     

Synthesis of a new oxime and its application to the construction of a highly selective and sensitive Co(II) PVC-based membrane sensor.

A cobalt(II) ion-selective membrane sensor has been fabricated from a poly vinyl chloride (PVC) matrix membrane containing a new oxime compound (oxime of 1-(2-oxocyclohexyl)-1,2-cyclohexanediol, OXCCD) as a neutral carrier, sodium tetraphenyl borate (NaTPB) as an anionic excluder and o-nitrophenyloctylether (o-NPOE) as a plasticizing solvent mediator. The membrane sensor exhibits a linear potential response in the concentration range of 1.0 x 10(-1) - 1.0 x 10(-6) M of Co2+. The electrode displays a Nernstian slope of 29.8 mV decade(-1) in the pH range of 3.5 - 8.0. The sensor also exhibits a fast response time of < 25 s. The detection limit of the proposed sensor is 9.0 x 10(-7) M (approximately 40 ng/ml), and it can be used over a period of two months. The selectivity of the sensor with respect to other cations (alkali, alkaline earth, transition and heavy metal ions) is excellent. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Co2+ with EDTA and for the direct determination of Co(II) in wastewater of the electroplating industry.     

2,6-bis-methylsulfanyl-[1,3,5]thiadiazine-4-thione as a Ag+-selective ionophore.

A silver ion-selective electrode was prepared with a polymeric membrane incorporating 2,6-bis-methylsulfanyl-[1,3,5]thiadiazine-4-thione as an ionophore, tri-n-butylphosphate (TBP) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive. The electrode exhibited a near-Nernstian response of 52 mV/decade over a wide linear concentration range of 1.0 x 10(-5) - 1.0 x 10(-1) M with a lower detection limit of 9.77 x 10(-6) M. The electrode exhibited excellent selectivity for silver ion over many of the alkali, alkaline-earth and transition metal ions. The electrode worked well over a wide pH range of 1.77 - 7.13. The response time of the electrode was less than 20 s. The sensor can be applied as indicator electrode for the potentiometric titration of Ag+ ions with Cl- ions.     

A highly selective and sensitive thorium(IV) PVC membrane electrode based on a dithio-tetraaza macrocyclic compound.

A poly(vinyl chloride)-based membrane composed of dithio-tetraaza macrocyclic compound as a neutral carrier with sodium tetraphenylborate (NaTPB) as an anion excluder and nitrobenzene (NB) as plasticizer was prepared and investigated as a Th(IV)-selective electrode. The electrode exhibits a Nernstian slope of 14.2 +/- 0.3 mV per decade over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with a detection limit of 8.0 x 10(-7) M between pH 3.5 and 9.5. The response time of the sensor is about 10 s and it can be used over a period of 5 months without any divergence in potential. The proposed membrane sensor revealed a good selectivity for Th(IV) over a wide variety of other metal ions and proved to be a better electrode in many respects than those reported in the literature. It was successfully applied as an electrode indicator as well as in the direct determination of thorium ions in standard and real samples.     

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.     

A novel wire-type lead-selective electrode based on bis (1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine

The preparation of a lead-selective electrode based on bis(1'-hydroxy-2'-acetonaphthone)-2,2'-diiminodiethylamine (L) as sensing material is reported. The plasticized PVC membrane containing 30% PVC, 67% ortho-nitrophenyloctylether (NPOE) and 3% ionophore L was directly coated on a graphite rod. This electrode exhibits a nearly Nernstian slope of 27.8+/-0.2 mV decade(-1) over a concentration range 10(-6)-10(-2) M with a detection limit of 4.0 x 10(-7) M. The response time of the electrode was found to be <20 s. The potential of the sensor was independent on pH variations in the range 5-7. The selectivity of the electrode towards lead ions over Na+, K+, Ag+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, La3+, Sm3+ and Er3+ ions was investigated. The prepared electrode was successfully used as an indicator for titration of a lead solution with a standard solution of EDTA. The applicability of the sensor for Pb2+ measurement in various synthetic and real samples has been also demonstrated.     

An Eu(III) sensor based on N,N-diethyl-N-(4-hydroxy-6-methylpyridin-2-yl)guanidine.

A highly selective poly(vinyl chloride)-based membrane sensor produced by using N,N-diethyl-N-(4-hydroxy-6-methylpyridin-2-yl)guanidine (GD) as active material is described. The electrode displays Nernstian behavior over the concentration range 7.0 x 10(-5) - 1.0 x 10(-1) M. The detection limit of the electrode is 5.0 x 10(-5) M. The best performance was obtained with the membrane containing 30% PVC, 55% benzyl acetate, 5% GD and 10% oleic acid. The response of the sensor is pH-independent in the range of 3.0 - 7.0. The sensor possesses satisfactory reproducibility, fast response time (< 20 s), and specially excellent discriminating ability for Eu(III) ion with respect to the alkali, alkaline earth, transition and heavy metal ions. The membrane sensor was used as an indicator electrode in potentiometric titration of Eu(III) ion with EDTA. It was also applied in determination of fluoride ions in mouth wash preparations.     

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.     

Bis(2-hydroxyacetophenone)ethylenediimine as a neutral carrier in a coated-wire membrane electrode for lead(II).

A coated-wire ion-selective electrode (CWISE), based on a Schiff base as a neutral carrier, was successfully developed for the detection of Pb(II) in aqueous solution. CWISE exhibited a linear response with a Nernstian slope of 29.4 +/- 0.5 mV/decade within the concentration range of 1.0 x 10(-5) - 1.0 x 10(-1) M lead ion. CWISE has shown detection limits of 5.0 x 10(-6) M. The electrode exhibited good selectivity over a number of alkali, alkaline earth, transition and heavy metal ions. This sensor yielded a steady potential within 10 to 20 s at a linear dynamic range. The electrode was suitable for use in aqueous solutions in a pH range of 2.0 to 5.0. Applications of this electrode for the determination of lead in real samples and as indicator electrode for potentiometric titration of Pb2+ ion using K2CrO4 are reported.     

Chromium(III) ion-selective electrode based on 4-dimethylaminoazobenzene

A PVC-based membrane of 4-dimethylaminoazobenzene reveals a Nernstian potentiometric response (with slope of 19.5+/-0.6 mV/decade and a correlation coefficient of 0.999) for Cr(III) over a wide concentration range (1.66 x 10(-6)-1.0 x10(-2) mol dm(-3)). The potential of this electrode is independent of pH in the range of 3.0-5.5. It has a fast response time of about 10 s and was used for a period of 3 months with good reproducibility. The detection limits of this membrane electrode was 8 x 10(-7) M. the proposed electrode has been used as an indicator electrode in the potentiometric titration of Cr(III) with EDTA. This sensor exhibits a very good selectivities for Cr(III) over a wide variety of metal ions.     

Copper(II)-selective electrode using 2,2'-dithiodianiline as neutral carrier

Poly(vinyl chloride) membrane electrode, that is highly selective and sensitive to Cu(II) ions, was developed by using 2,2'-dithiodianiline and dibutyl phthalate as carrier and plasticizer, respectively. The electrode exhibits good potentiometric response for Cu(II) over a wide concentration range (5.0x10(-2)-7.0x10(-7) mol l(-1)) with Nernstian slope of 30+/-1 mV per decade. The response time of the electrode is 10 s and it has been used for a period of one month and exhibits good selectivity towards Cu(2+) in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb(2+), Cd(2+) and Fe(+2) which are known to interfere with many other copper electrodes.     

Sulfate-selective PVC membrane electrode based on a strontium Schiff's base complex

A strontium Schiff's base complex (SS) can be used as a suitable ionophore to prepare a sulfate-selective PVC-based membrane electrode. The use of oleic acid (OA) and hexadecyltrimethylammonium bromide (HTAB), as additives, and nitrobenzen (NB), dibutyl phthalate (DBP) and benzyl acetate (BA) as solvent mediators, were investigated. The best performance was observed with a membrane composition PVC: NB: SS: HTAB of 30%: 62%: 5%: 3% ratio. The resulting sensor works well over a wide concentration range (1.0 x 10(-2)-1.0 x 10(-6) M) with a Nernstian slope of -29.2 mV per decade of sulfate activity over a pH range 4.0-7.0. The limit of detection of the electrode is 5 x 10(-7) M. The proposed sensor shows excellent discriminating ability toward SO4(2-) ions with regard to many anions. It has a fast response time of about 15 s. The membrane electrode was used to the determination of zinc in zinc sulfate tablets. The sensor was also used as an indicator electrode in the potentiometric titration of SO4(2-) against barium ion.     

A PVC plasticized sensor for Ni(II) ion based on a simple ethylenediamine derivative.

A new PVC membrane ion selective electrode which is highly selective towards Ni(II) ions was constructed using a Schiff base containing a binaphthyl moiety as the ionophore. The sensor exhibited a good Nernstian response for nickel ions over the concentration range 1.0x10(-1)-5.0x10(-6) M with a lower limit of detection of 1.3x10(-6) M. It has a fast response time and can be used for a period of 4 months with a good reproducibility. The sensor is suitable for use in aqueous solutions in a wide pH range of 3.6-7.4 and works satisfactorily in the presence of 25% (v/v) methanol or ethanol. The sensor shows high selectivity to nickel ions over a wide variety of cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for the direct determination of nickel content in real samples: effluent samples, chocolates and hydrogenated oils.     

Novel potentiometric sensor for monitoring beryllium based on naphto-9-crown-3.

A novel poly(vinyl chloride) (PVC) membrane electrode based on naphto-9-crown-3 was prepared and tested for the selective detection of beryllium ions. A suitable lipophilicity of the carrier and appropriate coordination ability were found to be essential for designing an electrode with good response characteristics. A PVC membrane with 9% naphtho-9-crown-3 carrier, 58% o-NPOE plasticizer, 3% tetraphenylborate anionic excluder and 30% poly(vinyl chloride) satisfied these requirements. The proposed sensor displayed a linear response to beryllium over a wide concentration range of 1.0 x 10(-1)-8.0 x 10(-6) M with a Nernstian slope of 29.5 mV per decade. The electrode showed very short response time (<15 s) and could be used in the pH range 3.5-9.0. The selectivity coefficient for alkali, alkaline earth, transition and heavy metal ions was smaller than 4.0 x 10(-4). The sensor was successfully used as an indicator electrode in the potentiometric titration of Be2+ with EDTA. The proposed Be(II) sensor was also used for the determination of Be2+ ions in binary mixtures.