All-solid-state potentiometric sensors sensitive to nonionic surfactants based on ionophores containing ethoxylate units

Earlier work of potentiometric Ion-selective electrodes (ISEs) sensitive to nonionic surfactants of the polyethoxylate type is further extended. The ISEs constructed were all-solid-state sensors with plasticized PVC membranes. The sensing material was a tetraphenylborate salt of the barium complex with a polyethoxylate nonionic surfactant. As membrane component, the combinations of two polyethoxylates of the nonylphenoxy type, which differed in the number of oxyethylene units (5 or 12), and two different plasticizers, (o-nitrophenyloctyl ether and o-nitrophenylphenyl ether), were tested. The response of these electrodes to different nonionic surfactants and the interference effect of several species has been evaluated. For all the types of tested electrodes, the sensitivities shown were ca. 30.0 mV dec(-1) and the limit of detection, ca. 10(-5) M, when a nonylphenoxyde with 12 oxyethylene units was used as standard. The membrane with the best response characteristics was then applied in potentiometric titrations of this kind of surfactants in the presence of Ba(2+) ion and using tetraphenylborate as the titrant.     

A cobalt(II)-selective PVC membrane based on a Schiff base complex of N,N′-bis(salicylidene)-3,4-diaminotoluene

A new PVC membrane electrode for Co²⁺ based on N,N′-bis(salicylidene)-3,4-diaminotoluene, an excellent neutral carrier, has been fabricated using sodium tetraphenylborate (NaTPB) as an anionic excluder and dioctylphthalte (DOP) as a solvent mediator. The electrode exhibits a linear potential response in the concentration range of 7.9 × 10⁻⁸ to 1.0 × 10⁻¹ M with a slope of 30 ± 0.2 mV per decade. The detection limit of the proposed sensor is 5.0 × 10⁻⁸ M and it can be used over a period of 5 months. The proposed sensor revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals and could be used in the pH range of 2.0-9.0. This electrode was successfully applied for the determination of Co²⁺in real samples and as an indicator electrode in potentiometric titration of cobalt ions.     

Novel platinum(II) selective membrane electrode based on 1,3-bis(2-cyanobenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-cyanobenzene)triazene (CBT) for highly selective determination of platinum(II) (in PtCl₄²⁻ form) is developed. The electrode showed a good Nernstian response (29.8 ± 0.3 mV decade⁻¹) over a wide concentration range (1.0 × 10⁻⁶ to 1.0 × 10⁻² mol L⁻¹). The limit of detection was 5.0 × 10⁻⁷ mol L⁻¹. The electrode has a response time of about 40 s, and it can be used for at least 1 month without observing any considerable deviation from Nernstian response. The proposed electrode revealed an excellent selectivity toward platinum(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, and it could be used in the pH range of 3.2-5.1. The practical utility of the electrode has been demonstrated by its use in determination of platinum ion in, alloy, tap, mineral and river water samples.     

Neutral carriers based polymeric membrane electrodes for selective determination of mercury (II)

The potentiometric response characteristics of mercury ion-selective membrane electrodes based on 2-amino-6-purinethiol (I₁) and 5-amino-1, 3, 4-thiadiazole-2-thiol (I₂) were described. Ion selectivities were tested for various plasticizers, which were used as solvent mediators to incorporate the ionophores into the membrane. Effects of experimental parameters such as membrane composition, nature and amount of plasticizers and additives, pH and concentration of internal solution on the potential response of Hg²⁺ electrodes were investigated. The best performance was obtained with the electrode having a membrane composition (w/w) of (I₁) (3.17%): PVC (31.7%): DOP (dioctylpthalate) (63.4%): NaTPB (sodium tetraphenylborate) (1.58%). The proposed electrode reveals a Nernstian response over Hg²⁺ ion in the concentration range of 7.0 × 10⁻⁸-1.0 × 10⁻¹ M with limit of detection 4.4 × 10⁻⁸ M. The electrode shows good discrimination toward Hg²⁺ ion with respect to most common cations. It shows a short response time (10 s) for whole concentration range and can be used for 2 months without any considerable divergence in potentials. For evaluation of the analytical applicability, the electrode was used in the determination of Hg²⁺ ion in different environmental and biological samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.     

A novel barium polymeric membrane sensor for selective determination of barium and sulphate ions based on the complex ion associate barium(II)-Rose Bengal as neutral ionophore

A simple, long life, rapid response and sensitive barium(II)-PVC membrane sensor that typically follows Nernstian behavior has been developed for the assay of barium(II) ions. The developed sensor has been made by incorporating the complex ion associate of barium(II)-Rose Bengal (Ba-RB) as an ionophore into a plasticized PVC matrix. The sensor is stable and exhibited fast potential response of 20 s and gave a good linear response with a Nernstian slope of 28.5 ± 0.4 mV/decade of activity within the concentration range 5 × 10⁻⁵ to 10⁻¹ M over a wide range of pH 4.5-10.0 for barium(II) ions. The developed sensor showed comparatively good selectivity for barium(II) ions with respect to other alkali, alkaline earth, transition and heavy metal ions. The plasticizer o-nitrophenyloctyl ether controlled significantly the calibration slope and the lifetime of the fabricated sensor. The proposed sensor was used successfully for the analysis of barium(II) ions in wastewater samples and in lithophone pigment with excellent recovery percentages in the range 98.9-99.8 ± 1.6%. The determination of sulphate in fresh and potable water samples with the developed sensor has been also achieved successfully. The described sensor provides a reliable means with good correlation with the data obtained by atomic absorption spectrometry (AAS) and other spectrophotometric methods for the analysis of trace amounts of barium(II) and/or sulphate ions in different matrices.     

Lead(II) ion-selective electrode based on polyaminoanthraquinone particles with intrinsic conductivity

A new polyvinylchloride membrane electrode was facilely prepared by using polyaminoanthraquinone (PAAQ) microparticles with an intrinsically electrical conductivity as a lead(II) ionophore. It is found that the electrode performance will significantly be improved with adding 1 wt% PAAQ microparticles and decreasing the membrane thickness. A 90 μm-thick membrane electrode consisting of PAAQ(salt):polyvinyl chloride:dioctylphthalate:sodium tetraphenylborate of 1:33:66:1 (wt) but without any traditional lead(II) ionophore achieved the optimal performance and exhibited a good Nernstian response for Pb(II) ions over a wide concentration range from 2.5 × 10⁻⁶ to 0.1 M with a slope of 28.9 mV/decade and a detection limit down to 776 nM. A reasonably short response time of 12 s was revealed together with a long lifetime over a period of around 4 months in a wide pH range between 2.8 and 5.2. A fixed interference method indicated that the electrode has an excellent selectivity for lead(II) ion over alkali, alkaline earth and other heavy metal ions. The proposed electrode has been also found to be a powerful indicator electrode for potentiometric titration of Pb(II) ions with EDTA. The electrode can be used to accurately monitor the Pb(II) pollution in environmental waters.     

Organically nanoporous silica gel based on carbon paste electrode for potentiometric detection of trace Cr(III)

A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5 wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0 × 10⁻⁸ to 1.0 × 10⁻³ M toward Cr(III) with a detection limit of 8.0 × 10⁻⁹ M and a Nernstian slope of 19.8 ± 0.2 mV decade⁻¹. The as-prepared electrode displayed rapid response (∼55 s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5-5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV-vis spectroscopy.     

Strontium(II)-selective electrode based on a macrocyclic tetraamide

A new PVC membrane electrode based on 5,7,12,14-dibenzo-2,3,9,10-tetraoxa-1,4,8,11-tetraazacyclotetradecane (I) as an ion carrier, o-nitrophenyloctyl ether (o-NPOE) as solvent mediator and sodium tetraphenylborate (NaTPB) as lipophilic additive was fabricated and investigated as Sr²⁺-selective electrode. The best performance was exhibited by the membrane having composition 8:200:4:120 (I:o-NPOE:NaTPB:PVC). The electrode exhibited a Nernstian response for strontium ion over a wide concentration range 3.98 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope of 29.0 ± 0.1 mV/decade of concentration and a detection limit of 2.82 × 10⁻⁶ M. It showed a response time of less than 10 s and could be used for at least 3 months without any divergence in potential. The proposed electrode showed a good discriminating ability towards strontium(II) ion over a wide variety of other metal ions including alkali, alkaline earth, transition, and heavy metal ions. The electrode can be used in the pH range of 2.5-10.5 and in mixtures containing up to 35% (v/v) non-aqueous content. It was used as an indicator electrode in potentiometric titration of strontium ion against EDTA.     

CuNiO nanoparticles assembled on graphene as an effective platform for enzyme-free glucose sensing

We utilized CuNiO nanoparticles modified graphene sheets (CuNiO–graphene) to the application of enzymeless glucose sensing. The hydrothermal synthesized CuNiO nanoparticles were successfully assembled on graphene sheets. Distinct from general method, the high quality pristine graphene was produced by chemical vapor deposition (CVD) and bubbling transferred on the electrode. Incorporating the excellent electronic transport of graphene and high electrocatalytic activity of CuNiO nanoparticles, the CuNiO–graphene nanocomposite modified electrode possessed strong electrocatalytic ability toward glucose in alkaline media. The proposed nonenzymatic glucose sensor exhibited wide linear range up to 16 mM (two parts, from 0.05 to 6.9 mM and 6.9–16 mM) and high sensitivity (225.75 μA mM⁻¹ cm⁻² and 32.44 μA mM⁻¹ cm⁻², respectively). Excellent selectivity and acceptable stability were also achieved. Such an electrode would be attractive to sensor construction for its good properties, simple operation and low expense.     

5,10,15-Tris(pentafluorophenyl)corrole as highly selective neutral carrier for a silver ion-sensitive electrode

A new highly selective silver(I) electrode was prepared with a PVC membrane using 5,10,15-tris(pentafluorophenyl)corrole as an electroactive material, 2-nitrophenyl octyl ether (o-NPOE) as a plasticizer and sodium tetraphenylborate (NaTPB) as an additive in the percentage ratio of 3:3:62:32 (corrole:NaTPB:o-NPOE:PVC, w:w). The electrode exhibited linear response with a near Nernstian slope of 54.8 mV/decade within the concentration range of 5.1 × 10⁻⁶ to 1.0 × 10⁻¹ M silver ions, with a working pH range from 4.0 to 8.0, and a fast response time of <30 s. Selectivity coefficients for Ag(I) relative to a number of interfering ions were investigated. The electrode is highly selective for Ag(I) ions over a large number of mono-, bi-, and tri-valent cations. Common interferents like Hg²⁺ and Cd²⁺ show very low interfering effect on the silver assay, which is valuable property of the proposed electrode. Several electroactive materials and solvent mediators have been compared and the experimental conditions were optimized. The sensor was applied to the determination of silver in real ore samples with satisfied results.     

Fabrication of polyaniline/carbon nanotube composite modified electrode and its electrocatalytic property to the reduction of nitrite

A polyaniline (PANI)/carbon nanotubes (CNTs) composite modified electrode was fabricated by galvanostatic electropolymerization of aniline on multi-walled carbon nanotubes (MWNTs)-modified gold electrode. The electrode thus prepared exhibits enhanced electrocatalytic behavior to the reduction of nitrite and facilitates the detection of nitrite at an applied potential of 0.0 V. Although the amperometric responses toward nitrite at MWNTs/gold and PANI/gold electrodes have also been observed in the experiments, these responses are far less than that obtained at PANI/MWNTs/gold electrode. The effects of electropolymerization time, MWNTs concentration and pH value of the detection solution on the current response of the composite modified electrode toward sodium nitrite, were investigated and discussed. A linear range from 5.0 × 10⁻⁶ to 1.5 × 10⁻² M for the detection of sodium nitrite has been observed at the PANI/MWNTs modified electrode with a sensitivity of 719.2 mA M⁻¹ cm⁻² and a detection limit of 1.0 μM based on a signal-to-noise ratio of 3.     

Nickel(II)-selective sensor based on dibenzo-18-crown-6 in PVC matrix

Nickel(II)-selective sensors have been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier dibenzo-18-crown-6 as electroactive material, sodium tetraphenylborate (NaTPB) as an anion excluder and tris-(2-ethylhexyl) phosphate (TEHP) as plasticizing solvent mediator. The membrane having the composition of crown ether:NaTPB:TEHP:PVC in the ratio 10:1:200:200 (w/w) exhibits best results with linear potential response in the concentration range of 1.0 × 10⁻⁵ to 1.0 × 10⁻¹ M and a Nernstian slope of 29.5 mV/decade of activity between 2.6 and 6.8. The sensor exhibits a fast response time of <25 s, is inert towards non-aqueous medium up to 15% (v/v) and was used over a period of 4 months with good reproducibility. It is selective over a number of mono-, bi- and trivalent cations. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Ni²⁺ against EDTA and also for the estimation of Ni²⁺ in some Indian brand chocolates.     

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.     

Organotin compounds: an ionophore system for fluoride ion recognition

Ion-selective properties were established for membrane electrodes prepared by using organotin compounds of type (L^CNRSnF₂)_n, (R = n-Bu (I), = Ph (II)) and (L^CNSnF₃)_n (III) (L^CN = C₆H₄(CH₂NMe₂)-2). Electrodes formulated with the optimized membranes containing the organotin compounds I-III as ionophores and sodium tetraphenylborate (10-30%) exhibited high selectivity for fluoride over other anions. An electrode prepared with ionophore II using dibutyl phthalate as the plasticizer and 15% sodium tetraphenylborate (NaTPB) as anion additive, possesses the best potentiometric response characteristics. It shows a detection limit of 7.9 × 10⁻⁷ M with a slope of 62.7 mV decade⁻¹ of activity in buffer solutions of pH 5.5. The interference from other anions is suppressed under this optimized measurement conditions. An entirely non-Hofmeister selectivity sequence (F⁻ > CH₃COO⁻ > Cl⁻ > I⁻ ∼ Br⁻ >ClO₄⁻ > NO₂⁻ > NO₃⁻ > SCN⁻) with remarkable preference towards fluoride is obtained. The influence on the electrode performances by anion additive was studied, and the possible response mechanism was investigated by UV-vis spectra. The electrode has been used for direct determination of fluoride in drinking mineral water with satisfactory results.     

Potentiometric determination of cetylpyridinium chloride using a new type of screen-printed ion selective electrodes

A new type of screen-printed ion-selective electrode for the determination of cetylpyridinium chloride (CPC) is presented. These new electrodes involve in situ, modified and unmodified screen-printed ion-selective electrodes for the determination of CPC. The screen-printed electrodes (SPEs) show a stable, near-Nernstian response for 1 × 10⁻² to 1 × 10⁻⁶ M CPC at 25 °C over the pH range 2-8 with cationic slope 60.66 ± 1.10. The lower detection limit is found to be 8 × 10⁻⁷ M and response time of about 3 s and exhibit adequate shelf-life (6 months). The fabricated electrodes can be also successfully used in the potentiometric titration of CPC with sodium tetraphenylborate (NaTPB). The analytical performances of the SPEs are compared with those for carbon paste electrode (CPE) and polyvinyl chloride (PVC) electrodes. The method is applied for pharmaceutical preparations with a percentage recovery of 99.60% and R.S.D. = 0.53. The frequently used CPC of analytical and technical grade as well as different water samples has been successfully titrated and the results obtained agreed with those obtained with commercial electrode and standard two-phase titration method. The sensitivity of the proposed method is comparable with the official method and ability of field measurements.     

8-hydroxyquinoline based neutral tripodal ionophore as a copper (II) selective electrode and the effect of remote substitutents on electrode properties

New PVC membrane ion selective electrodes based on 1,3,5-Tris(8-quinolinoxymethyl)-2,4,6-trimethylbenzene (MO8HQ) are reported. The basic sensing material belongs to the group of tripodal ionophores. Also their derivatives prepared by placing suitable substitutents at fifth position of 8-oxine moiety, i.e, 1,3,5-Tris(5-chloro-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5CHQ), 1,3,5-Tris(5-benzoyl-8-quinolinoxymethyl)-2,4,6-trimethylbenzene (5BHQ) and 1,3,5-Tris[(5-phenylhydroxymethylene)-8-quinolinoxymethyl]-2,4,6-trimethylbenzene (HYD-8HQ) ionophores have also been used to make copper-selective membrane electrodes. Among all the four electrodes, MO8HQ and HYD-8HQ ionophores based electrodes show excellent response towards Cu (II) ions. The electrodes having composition 33% PVC, 4% MO8HQ and 63% dibutyl phthalate (DBP) and 33% PVC, 6% HYD-8HQ, 63% dibutyl phthalate (DBP) exhibit a good Nernstian response to Cu (II) ions in the range of 1.0 × 10⁻⁶ to 1 × 10⁻¹ M. The electrode shows a reasonably fast response time of 15 s. The effect of pH and electrode response is also reported. It shows good selectivity for Cu (II) ions in comparison to heavy metal ions, transition metal ions and for alkali and alkaline earth metal ions. The electrode response and selectivity remains unchanged for at least 5 months. The electrode can be used as an indicator electrode in the potentiometric titration of Cu (II) ions with EDTA.     

A SO2-selective electrode based on a Zn-porphyrin for wine analysis

This work describes the assessment of a SO₂-selective electrode based on the use of the neutral carrier 5,10,15,20-tetraphenyl(porphyrinate)zinc(II) in a PVC membrane plasticized with 2-nitrophenyl phenyl ether. After being conditioned in 2 mol L⁻¹ diethylamine solution for 24 h, the electrode exhibited selective anionic response toward the analyte in a concentration interval of more than four decades, with an slope of −59.5 mV dec⁻¹, a practical detection limit of 3.7 × 10⁻⁶ mol L⁻¹ and a low limit of linear range of 7.2 × 10⁻⁶ mol L⁻¹. The response mechanism is based on the displacement of the diethylamine:metalloporphyrin complex equilibrium within membrane bulk, inducing a variation in the cationic-sites to ionophore ratio. In turn, free hydroxyl ions are complexed by the displaced ionophore in a ratio 1:1 and translated as single negative charge nernstian response. Finally, the selectivity of the electrode is evaluated in view of its application to wine analysis. Results had high accuracy and precision when compared with a reference method.     

A new ion-selective electrode for anionic surfactants

The new ligand 7-methyl-7,13-di-octyl-1,4,10-trioxa-13-aza-7-azonia-cyclopentadecane (L¹) has been designed, synthesised and used as ionophore in the development ion-selective electrodes for anionic surfactants. Different PVC-membrane anionic-surfactants-selective electrodes were prepared by using L¹ as ionophore and bis(2-ethylhexyl)sebacate (BEHS), dibutyl phthalate (DBP) and nitrophenyl octyl ether (NPOE) as plasticizers. The PVC-membrane electrode containing L¹ and NPOE (electrode E1) showed a Nernstian response to lauryl sulfate with a slope of −59.5 mV per decade in a range of concentrations from 1.3 × 10⁻⁶ to 6.8 × 10⁻³ M and a detection limit of 6.0 × 10⁻⁷ M. The electrode E1 also showed a reasonable response to other alkyl sulfates and alkylbenzene sulfonates, whereas it does not respond to carboxylates and to cationic and non-ionic surfactants. A similar electrode to E1 but additionally containing the cationic additive n-octylammonium bromide was also prepared (electrode E2) and compared with the response of E1. Selectivity coefficients for different anions with respect to lauryl sulfate were determined by means of the fixed interference method considering lauryl sulfate as the principal anion and using a concentration of 1.0 × 10⁻² mol dm⁻³ for the corresponding interfering anion. The selectivity sequence found for the electrode E1 was: LS⁻ > SCN⁻ > ClO₄⁻ > CH₃COO⁻ > I⁻ > HCO₃⁻ > Br⁻ > NO₃⁻ > NO₂⁻ > Cl⁻ > IO₃⁻ > phosphate > SO₃²⁻ > C₂O₄²⁻ > SO₄²⁻. Electrode E1 showed remarkably better selectivity coefficients than electrode E2.     

Enhanced sensing of ascorbic acid, dopamine and serotonin at solid carbon paste electrode with a nonionic polymer film

A nonionic poly(2-amino-5-mercapto-thiadiazole) film was electrodeposited on a solid carbon paste electrode via a potential scanning procedure, and used for amperometric sensing of ascorbic acid (AA), dopamine (DA) and serotonin (ST). The highly electrocatalytic activity of the sensor to the three analytes was demonstrated from the sensitive and well separated voltammetric signals. The polymer film did not show significant accumulation effect on all the three species, reducing the fouling and deactivation of the electrode surface as well as the mutual interference among the analytes. The sensor achieved amperometric sensitivities of 1.92 nA (nmol L⁻¹)⁻¹ cm⁻² to AA in the linear range of 0.025-1.95 μmol L⁻¹, 3.76 nA (nmol L⁻¹)⁻¹ cm⁻² to DA and 7.00 nA (nmol L⁻¹)⁻¹ cm⁻² to ST both in the linear range of 0.02-1.56 μmol L⁻¹. The lowest detection limits were found to be 1.5, 0.7 and 0.4 nmol L⁻¹ for AA, DA and ST, respectively. This sensor was successfully employed for the successive determination of AA, DA and ST in pharmaceutical samples. The good antifouling property and reproducibility of the proposed sensor can be attributed to the nonionic polymer film without electrostatic attraction to the ionized species in the solutions.     

Schiff bases as cadmium(II) selective ionophores in polymeric membrane electrodes

The construction and performance characteristics of polymeric membrane electrodes based on two neutral ionophores, N,N′-[bis(pyridin-2-yl)formylidene]butane-1,4-diamine (S₁) and N-(2-pyridinylmethylene)-1,2-benzenediamine (S₂) for quantification of cadmium ions, are described. The influences of membrane compositions on the potentiometric response of the electrodes have been found to substantially improve the performance characteristics. The best performance was obtained with the electrode having a membrane composition (w/w) of (S₁) (2.15%):PVC (32.2%):o-NPOE (64.5%):KTpClPB (1.07%). The proposed electrode exhibits Nernstian response in the concentration range of 7.9 × 10⁻⁸ to 1.0 × 10⁻¹ M Cd²⁺ with limit of detection 5.0 × 10⁻⁸ M, performs satisfactorily over wide pH range (2.0-8.0) with a fast response time (10 s). The sensor has been found to work satisfactorily in partially non-aqueous media up to 30% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 2 months. The analytical usefulness of the proposed electrode has been evaluated by its application in the determination of cadmium in real samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.