Matched Potential Method Research Articles

Highly selective and sensitive potentiometric determination of favipiravir in COVID-19 antiviral drug formulations

In this study, a novel all-solid-state electrochemical sensor based on favipiravir-tetraphenylborate (FAV-TPB) electroactive material was developed and reported for FAV’s highly selective and sensitive potentiometric determination in COVID-19 antiviral drug formulations. All-solid-state FAV selective sensor was fabricated by mixing and properly pressing FAV-TPB, graphite (G), multi-walled carbon nanotube (MWCNT), and paraffin oil (PO). In order to obtain the best sensor response, the sensor component ratios were optimized. The most satisfying response characteristics was obtained with the sensor composition FAV-TPB:G:MWCNT:PO in the ratio 32.5:42.5:5:20 (w/w %). The developed sensor displayed a wide linear near-Nernstian response to FAV over the concentration of 1.0 × 10−6 − 1.0 × 10−1 molL−1 with a slope of 53.6 ± 1.4 mV (R2 = 0.9997). The detection limits of the sensor was calculated as 6.0 × 10−7 molL−1, respectively. The dynamic response time of the sensor was 7 s, and the sensor exhibited fairly reproducible potentiometric responses. In the pH range of 6.0–8.0, the sensor’s potential response was not affected by the pH change of the test solutions. The improved sensor had a wide temperature tolerance, and its response remained unchanged in the 10–40 ℃ temperature range. The interference effect of some chemical and biological species was evaluated by the matched potential method and separate solution method. The sensor worked stable for 12 weeks without any considerable change in its potential response. The analytical applications of the sensor were successfully carried out with the potentiometric titration of FAV with sodium tetraphenylborate solution and also the direct determination of favipiravir in COVID-19 antiviral drug formulations.

Preparation, characterization and application of a novel selective mercury electrode using natural Epoxide as a green anion carrier

A novel modified carbon paste electrode that was based on Epoxide natural rubber 30 phr (electrode V) and Epoxide natural rubber spent coffee 5 phr (electrode X) as a chemical modifier was developed and used to quantify mercuric ions in water samples. The developed electrode exhibits a Nerstian response within ranges of 10−7 – 10−1 and 10−8 – 10−1 mol L−1, and the obtained limits of detection (LOD) were 4.5 × 10−8 and 6.9 × 10−9 mol L−1 for electrode IV and Electrode VII, respectively. The paste showed that it could be utilized for more than 125 and 140 days without showing any signs of deterioration. Moreover, the sensors were proved to be useable within pH ranges of 1.5 to 5.0, and 1.0 to 5.5, for the respectively mentioned electrodes. The isothermal coefficients were found to be 0.00011 and 0.00017 V/oC for electrode IV and electrode VII, respectively. Match potential method (MPM) selectivity coefficients show that mercury(II) ions have a high selectivity. Mercury may be distinguished from other cations quite well with the suggested electrode. The suggested sensors were applied successfully in the quantification of Hg(II) ions in real-world petroleum water samples. The unique abilities of these Epoxide natural rubber 30 phr is the key driver for adoption of (ISEs) principles to improve environmental friendliness of the analytical methods. The results from the developed approach and those from atomic absorption spectrometry (AAS) were statistically comparable.

A new screen-printed electrode for selective determination of bismuth in different authentic samples

A new potentiometric method based on the screen-printed ion-selective electrode (SPISE) was described for the determination of Bi(III) ion in different authentic samples. The novelty is based on, for the first time, the utilization of the cerium zirconium phosphotungstate (CZPT) in a screen-printed electrode (SPE) as a sensing material. In the literature, there is no screen-printed ion-selective electrode for the determination of Bi(III) ion. The influences of the paste composition, different conditioning parameters and foreign ions on the electrode performance were investigated. The reversibility and also response time of the electrode have been studied. The electrode showed a Nernstian response of 18.2 mV decade−1 in the concentration range of 3.3 × 10−7–1 × 10−1 mol. L−1. The electrode was found to be usable within the pH range of 3.5–8.0 and exhibited a fast response time, limit of detection (LOD) (1 × 10−7 mol. L−1), limit of quantification (LOQ) (3.33 × 10−7 mol. L−1), long lifetime and good stability. The matched potential method (MPM) was applied to determine the selectivity coefficient. The isothermal temperature coefficient (dEo/dt) of the electrode was calculated. The electrode was successfully applied for the determination of Bi(III) ion in different authentic samples. By comparing the current results with those obtained using inductively coupled plasma optical emission spectrometry, the nominated Bi(III) screen-printed ion-selective electrode has attained acceptable and efficient performance.

Applicability of a synthesized melamine based covalent organic framework as a novel ionophore for the potentiometric determination of mercury (II): Computational and experimental studies

In this research, the complexation of a recently synthesized covalent organic framework (schiff base network1) with 10 different cations was investigated by QTAIM (quantum theory of atoms in molecules) computations. The theoretical results showed the schiff base network1 interactions with Hg2+ is considerably stronger than other cations and it can be used as an selective ionophore for the development of a potentiometric sensor to determination of Hg2+. Therefore, a Hg2+ selective PVC membrane coated graphite electrode was developed based on schiff base network1. The best response was observed form the membrane composition of PVC (32 %), Nitrobenzene (60 %), sodium tetraphenylborate (2 %), and schiff base network1 (6 %). The designed sensor showed an excellent Nernstian response to Mercury (II) (29.8 mV. Decade−1) over a wide activity range from 1 × 10−7 to 5 × 10−3 and the detection limit of the proposed potentiometric sensor was 8 × 10−8. The effect of different interfering species on the potentiometric response of the suggested electrode was scrutinized by matched potential method (MPM) and no interference was observed. The performance of the developed electrode in partially non-aqueous mediums was also checked out and the obtained results showed the electrode can also be utilized in systems containing %20 organic solvents (ethanol and acetone). The response time and lifespan of the electrode were <10 S and 16 weeks respectively. In the end, the analytical performance of the fabricated sensor for the determination of Hg (II) in three different effluent samples was scrutinized and the obtained results were compared with a standard spectrophotometric technique.

Fabrication of Novel Potentiometric Sensor for Lead Ion Detection in Blood Samples: Experimental and Theoretical Approaches

One of the significant health problems in some developing countries such as Iran is lead toxicity. Potentiometric plasticizer-free Pb2+ selective electrode based on a simple and biocompatible ionophore, curcumin, for lead (II) detection in erythrocytes have been developed. Glassy carbon electrode modification was done with curcumin as an ionophore. Curcumin and its interaction with lead (II) were characterized using FT-IR, FE-SEM, and UV–Vis spectroscopic techniques. Match potential method (MPM) was applying for determining selectivity coefficients of the proposed sensor. Furthermore, the structures were optimized in various media for both tautomeric structures of curcumin, and then the binding mechanism was supported by DFT calculation, being in a high correlation and agreement by experiment. Also, noncovalent interaction studies were done to obtain a description of the sensing process. The fabricated ISE based on photocurable self-plasticizing (n-butylacrylate) membrane with curcumin shows a potentiometric response with a Nernstain slop of 28.348 ± 0.68 mV per decade in a linear range from 1.0 × 10-9 to 1.0 × 10-2 and detection limit of 3.98 × 10-10 M. The sensor' s response time was about 20 s at room temperature. The sensor shows a sensitive detection of Pb2+ in human erythrocytes and standard solutions.

Low-cost Pencil-Graphite Multi-electrodes for Simultaneous Detection of Iron and Copper

Herein, two novel ion-selective electrodes are reported for simultaneous potentiometric determination of Fe3+ and Cu2+ ions. The liquid polymeric membrane components were optimized and the resulting pencil graphite electrodes gave Nernstian slopes of 20.7 mV/decade and 31.2 mV/decade with lower detection of limit of 1×10-6 mol L-1 and 2×10-6 mol L-1, and wide pH range of 1.5-3.5 and 2.0-4.7 for Fe3+ and Cu2+ ions, respectively. The electrodes exhibited very fast response time (&amp;lt;6 s). In addition, the electrodes exhibited high selectivity for Fe3+ and Cu2+ ions against different cations, which were tested by matched potential method. The sensing platform using the optimized electrodes were integrated with the Internet of Things concept are suitable for simultaneous monitoring of Fe3+ and Cu2+ in real samples with high accuracy and precision.

Potentiometric Sensor Based on Molecularly Imprinted Polymer for Determination if Tramadol in A Biologic Fluid Model and Urine

In this study, a potentiometric sensor based on a molecularly imprinted polymer (MIP) was developed for determination of tramadol. At optimized condition the electrode exhibited a Nernestian response (30.5±1.0 mV/decade) in a concentration range of (1×10-6 to 1×10-2 M). The potential response of the electrode was constant in the pH range of 1.0-9.0. The electrode demonstrated a response time about 15s. Selectivity coefficient of the sensor with structural similarity to tramadol was evaluated by matched potential method (MPM). The electrode was examined successfully for determination of tramadol in biological fluids and urine with a good accuracy and precision

Potentiometric sensors selective for Cu(II) determination in real water samples and biological fluids based on graphene and MWCNTs modified graphite electrodes

Three newly synthesized Cu(II) ion selective electrodes based on 1,8-dihydoxyanthraquinone (DHAQ), as an ionophore, have been developed. Sensor I was modified with DHAQ only, while sensors II and III were modified with graphene and multi-walled carbon nanotubes (MWCNTs), respectively, in addition to DHAQ to improve conductivity and transduction of chemical signal to electrical signal. Under optimized conditions, the electrodes I, II and III revealed Nernstian slopes of 29.78 ± 0.17, 30.25 ± 0.12, and 30.55 ± 0.19 mV decade-1, respectively, at 25±1° C covering a wide concentration range from 1 × 10-6 to 1 × 10−1 mol L-1 for sensors I and II and from 1 × 10-5 to 1 × 10−1 mol L-1 for sensor III with detection limit values of 8 × 10−7, 5 × 10−7, and 3.3 × 10−6 mol L-1, respectively. The response of the proposed electrodes was very fast and independent of pH in the range of 2.4-6.5 and the response mechanism was studied using IR, SEM and EDX analyses. Selectivity coefficients were determined by applying separate solution method (SSM) and matched potential method (MPM), where the obtained values indicated the good discrimination of Cu(II) from other cations by the proposed sensors. The developed sensors were used successfully for quantitative determination of Cu(II) ions in different matrix of spiked real water samples and biological fluids (urine and serum). These sensors were also used successfully as indicator electrodes in the potentiometric titration of Cu(II) with EDTA.

A Liquid Membrane Mercury Selective Electrode Based on 2-(N-pipyridino Methyl)-1-Cyano Cyclohexanol as a Novel Neutral Carrier

2-(N-pipyridino methyl)-1-cyano cyclohexanol was synthesized, characterized and used as an ionophore in construction of polyvinyl chloride (PVC) potentiometric sensor for Hg2+ determination. The best result was obtained with membrane composition of PVC (29%), sodium tetraphenylborate as ionic additive (1%), 2-(N-pipyridino methyl)-1-cyano cyclohexanol (12%) and dibutylphthalate (58%). The designed electrode showed an acceptable Nernstian slope (29.1 mV/decade) for Hg2+ over a wide concentration range from 5 × 10–7 to 1 × 10–2 M with a detection limit of 2.5 × 10–7 M. The potential response was independent from pH in the range of 6.0–9.0 and the sensor response time was relatively short (~25 s). The sensor performance was invariable for at least 6 weeks. Electrode selectivity was evaluated by matched potential method. Finally, the proposed sensor was used as an indicator electrode in potentiometric titration of Hg2+ with ethylenediaminetetraacetic acid and in direct determination of mercury(II) in aqueous samples with admissible accuracy and high reproducibility.

Application of 1,4-Diaminoanthraquinone as a New Sensing Material for Fabrication of a Iron(III)-Selective Modified Carbon Paste Electrode

In the present work, a novel sensitive electrochemical potentiometric sensor for sensing Fe3+ ions based on 1,4-diaminoanthraquinone (DAQ) as a hydrophobic selector element was prepared to implement as an ion selective carbon paste electrode in the aqueous solutions. The adequate amounts of ionophore (5%), paraffin oil (25%) as a binder, Nanosilica (NS: 0.5%) multi-wall carbon nanotubes (MWCNTs: 1%) as a modifier, and graphite powder (68.5%) as an inert matrix was occupied to form the paste. This new FeCP sensor demonstrated a Nernstian slope of 19.7 ± 0.7 mV per decade over widish linear range between 1.0 × 10–8 to 1.0 × 10–2 mol L–1 at working pH range of 1.9–5.0 in the optimized conditions. The average elapsed time to response of electrode was about ~6 s for concentrations from lower (1.0 × 10−8 mol L–1) to higher (1.0 × 10−2 mol L–1) of Fe3+ ion solution. The selectivity of electrode toward Fe3+ ions in comparison with other cations was studied by matched potential method. The making FeCP sensor has been put to use successfully as an indicator electrode in analytical applications such as the potentiometric titration and determination of iron(III) ion in blend of different ions.

A New Highly Selective Neodymium(III) Polyvinylchloride Membrane Electrode Based on 4-Hydroxypyrrolidine-2-Carboxylic Acid as an Active Material

The present paper describes the fabrication of a new polyvinylchloride (PVC) membrane electrode for the determination of Nd(III) ion based on 4-hydroxypyrrolidine-2-carboxylic acid (LHP) as an active material along with sodium tetraphenyl borate (NaTPB) as an anionic additive and acetophenone (AP) as solvent mediator. The optimum composition (%, w/w) of the best performing membrane contained 66 AP, 30 PVC, 2 NaTPB and 3 LHP. The basic analytical parameters of this electrode such as slope characteristics, detection limit, response time, selectivity and pH effect were assessed. The electrode displayed a Nernstian response in terms of slope (20.5 ± 0.4 mV per decade) and response time (~8 ± 1 s) over a wide neodymium ion concentration range of 10–6 to 10–2 M with a detection limit of 7.5 × 10−7 M. The potentiometric response of the electrode was constant in the pH range of 3.2‒8.9. According to the selectivity coefficients determined by the matched potential method, the interference of many common alkaline, alkaline earth, transition, heavy metals and specially lanthanide ions in determination of Nd(III) ion was very low. The proposed electrode has been successfully used as an indicator electrode in the potentiometric titration of Nd(III) ion with EDTA and applied for determination of Nd(III) ion in mixtures of different ions.

Development of a potentiometric sensor for europium(III) based on N, N, N′, N′-tetraoctyldiglycolamide (TODGA) as the ionophore

A polymer inclusion membrane (PIM) with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) as the ionophore and polyvinyl chloride (PVC) as the base polymers was synthesized and evaluated for potentiometric membrane sensing of Eu3+ ions. Effects of membrane composition, inner filling solution and pH on the electrode performance were investigated and it was found that the membrane with a composition of 30.3% TODGA, 9.1% NaTPB and 60.6% PVC showed a wide linear dynamic range (1.5×10−6M to 1.2×10−2M) with a slope of 17.3±0.1mV per decade with 1.2×10−6M as the limit of detection for Eu3+. Interference from mono-, di-, tri-, tetra- and hexa-valent ions was investigated by matched potential method. The sensor was also tested as an indicator electrode in the titration of Eu3+ with standard EDTA solution. The response time of the proposed sensor was found to be <10s. The life time of the sensor electrode was found to be one month under optimized storage conditions. The potentiometric sensor as developed was employed in the determination of Eu3+ in the synthetic mixture of uranyl nitrate and europium nitrate, after the removal of major matrix using 30% TBP-n-dodecane. The analytical results, compared with those obtained from inductively coupled plasma - atomic emission spectroscopy (ICP-AES), showed good agreement between the two methods.

Application of 2‐(benzyliminomethyl)‐6‐methoxy‐4‐(4‐methoxyphenyl‐azo)phenol in construction of ion‐selective PVC membrane electrode for determination of copper (II) in mineral water sample

The potentiometric characteristics of a new Cu2+‐selective electrode based on 2‐(benzyliminomethyl)‐6‐methoxy‐4‐(4‐methoxyphenyl‐azo) phenol as an efficient ionophore has been evaluated. The effects of influential parameters on the potentiometric responses such as the amount of plasticizer, the amount of ionophore, pH of the sample solution, and the effect of coexisting ions on the electrode signal were subsequently investigated. The selectivity of the electrode was assessed by calculating the selectivity coefficients using the matched potential method. The optimum ratio of the amount of materials required for the preparation of the electrode was found to be 1.7: 32.1: 64.2: 2.0 corresponding to carboxylated PVC, dimethyl sebacate as solvent mediators, potassium tetrakis (p‐chlorophenyl) borate as the anion localizing agent, and ionophore, respectively. The electrode had a fast response (7s) as well as a satisfactory Nernstian slope (29.26±0.91 mV/decade) to Cu2+ over a wide concentration range of 2.0×10−6‐ 5.0×10−2 M with a low detection limit of 5.9×10−7 M. The developed sensor was successfully used for the potentiometric titration of Cu2+ ion with EDTA and subsequently, efficient determination of this metal ion in a mineral water sample was performed.

A new PVC matrix membrane sensor for determination of praseodymium(III) ion based on bis(salicylaldehyde)thiocarbohydrazone as an ion carrier

The sufficient amounts of bis(salicylaldehyde) thiocarbohydrazone (STCH) as a lipophilic selective element (3%, w/w), sodium nitrobenzene (NB) as a plasticizer (64%, w/w), tetraphenyl borate (NaTPB) as an anionic additive (3%, w/w), and poly vinyl chloride (PVC) as a polymeric matrix (30%, w/w) was employed to form a PVC membrane of a new Pr3+ ions selective sensor to apply as an indicator electrode in analytical applications. The best electrode response was observed in the slope (19.5 ± 0.7 mV per decade) over a wide concentrations from lower (1.0 × 10−6 mol L–1) to higher (1.0 × 10−2 mol L–1) of Pr3+ ion solution with a detection limit of 8.5 × 10–7 mol L–1. This electrode showed the fast response time about 10 second for praseodymium ion concentration range of 1.0 × 10–6 to 1.0 × 10–2 mol L–1, in the pH range of 2.3–7.9. The matched potential method was applied to study the selectivity of electrode toward Pr3+ ions in comparison with many common cations. The results showed the negligible disturbance of all other cations on the proposed praseodymium(III) electrode. The making sensor has been employed successfully as an indicator electrode in the potentiometric titration of praseodymium(III) solution with EDTA at pH 6.0. Moreover the applicability of the sensor was studied in determination of Pr3+ ion in mixtures of different ions.

Construction of a new Ho3+ PVC-membrane electrochemical sensor based on N,N′-dipyridoxyl(1,4-butanediamine)

N,N′-dipyridoxyl(1, 4-butanediamine) (PYBA) (2 wt % ), nitrobenzene (66 wt %), sodium tetra phenyl borate (2 wt ), and poly vinyl chloride (30 wt %) were applied to create a PVC membrane in Ho3+ selective electrode (Ho-SE). Over the concentration range of 1.0 × 10‒5 to 1.0 × 10‒2 M in holmium(III) solution a linear response with lower detection of limit equal 4.0 × 10‒6 M was exhibited by new holmium(III) sensor. Ho-SE possessed a Nernstian slope of 20.1 ± 0.8 mV decade‒1 in very short time spans (~9 s). The potential response of electrode remains without any changes over a pH range of 2.77–8.71. The selectivity coefficient data which was considered by matched potential method for variety of common cations indicated no significant interference. An acceptable recovery for Ho3+ in the blend of several cations has been achieved. The utility of Ho-SE in potentiometric titration as an end point indicator electrode gave successfully results.

Potentiometric and surface topography studies of new carbon-paste sensors for determination of thiamine in Egyptian multivitamin ampoules

We report here for the first time two potentiometric carbon-paste sensors for determination of thiamine chloride hydrochloride in aqueous solutions. The proposed sensors use the ion-pair of thiamine with tetraphenylborate as an electro-active species and dibutyl phthalate (sensor I) or o-nitrophenyloctyl ether (sensor II) as solvent mediators. The effect of solvent mediator was studied using dibutyl phthalate, o-nitrophenyloctyl ether, ethylhexyl adipate, dioctyl phthalate, tricresyl phosphate and paraffin oil. The slopes of the calibration graphs are 29.49±0.24 and 29.60±0.15mV/decade for sensors (I) and (II), respectively. The sensors are able to detect down to 5.25×10−6 and 3.57×10−6 for (I) and (II), respectively. Both sensors show reasonable thermal stability and fast response time. The selectivity coefficients obtained from the matched potential method indicate high selectivity of the proposed sensors toward thiamine over commonly interfering cations. Sensor (I) has a lifetime of only 1–2days; however, sensor (II) remains usable for up to one month. Analytical applications to pure solutions and Egyptian multivitamin ampoules show excellent recovery values ranging from 97.92 to 103.72% and 97.21 to 102.19% for sensors (I) and (II), respectively. Moreover, the precision and reproducibility of the sensors are indicated from the low values of %RSD of five replicate measurements. In addition, the surface topography of the sensors was studied using scanning electron microscopy to investigate the effect of chemical modification on the surface structure.

Fabrication of a new nanocomposite modified carbon paste Al3+-ion selective electrode based on N,N′-dipyridoxyl (1,2-cyclohexanediamine) (PYCA) as an active material

Construction and feature of a nanocomposite modified carbon paste electrode for aluminum(III) ion determination based on N,N′-dipyridoxyl (1,2-cyclohexanediamine) (PYCA) as a novel selector material will be covered by this paper. The optimum composition, Nernstian slope/linear range/detection limit in the forms of calibration graph, response time, utilizable pH range, repeatability and precision of measurements of the aluminum(III) ion using the new fabricated Al3+-CPE was evaluated. The optimal composition which performed over Al+3 ion concentration range 1.0 × 10−8 mol L−1–1.0 × 10−1 mol L−1 with near-Nernstian slope equal 20.9 ± 0.2 mV decade−1 and low detection limit about 5.0 × 10−9 mol L−1, was formed of ionophore (PYCA 3 %), binder (paraffin oil 30 %), modifier [multi-wall carbon nanotubes (MWCNTs) 1 %] & [Nanosilica (NS) 0.5 %], and inert matrix (graphite powder 65.5). The request time to give rise Nernstian response of electrode for concentrations from 1.0 × 10−8 mol L−1 to 1.0 × 10−1 mol L−1 of Al3+ ion solution was estimated about ~6 s. The new Al3+-CPE was applied in pH range 2.0–5.0 with no consequential change in potential response. To verify the selectivity of electrode toward aluminum(III) ion in the presence of different metallic cations, matched potential method was used. The obtain results in analytical applications reflect the excellent ability of this electrode to play the role as endpoint indicator electrode in both titration and direct potentiometric measurements.

Highly selective direct determination of chlorate ions by using a newly developed potentiometric electrode based on modified smectite

A novel polyvinyl chloride membrane chlorate (ClO3−) selective electrode based on modified smectite was developed for the direct determination of chlorate ions and the potentiometric performance characteristics of its were examined. The best selectivity and sensitivity for chlorate ions were obtained for the electrode membrane containing ionophore/polyvinylchloride/o-nitrophenyloctylether in composition of 12/28/60 (w/w%). The proposed electrode showed a Nernstian response toward chlorate ions at pH=7 in the concentration range of 1×10−7–1×10−1M and the limit of detection was calculated as 9×10−8M from the constructed response plot. The linear slope of the electrode was −61±1mVdecade−1 for chlorate activity in the mentioned linear working range. The selectivity coefficients were calculated according to both the matched potential method and the separate solution method. The calculated selectivity coefficients showed that the electrode performed excellent selectivity for chlorate ions. The potentiometric response of electrode toward chlorate ions was found to be highly reproducible. The electrode potential was stable between pH=4–10 and it had a dynamic response time of <5s. The potentiometric behavior of the electrode in partial non-aqueous medium was also investigated and the obtained results (up to 5% (v/v) alcohol) were satisfactory. The proposed electrode was used during 15 weeks without any significant change in its potential response. Additionally, the electrode was very useful in water analysis studies such as dam water, river water, tap water, and swimming pool water where the direct determination of chlorate ions was required.

Qualification and Quantification Analyses of Iron (III) Ions in a Variety of Samples, Using Nano-Structured Metal-Oxide Based Electrochemical Sensors

The purpose of this work is to design and develop a sensitive and selective nanostructured electrochemical sensor for the analyses of iron (III) ions in different samples, such as drinking water, seawater, pharmaceutical products, soil and food. Iron is an essential metal especially for biological systems since it plays an important role in many metabolic pathways, has an effective role in oxygen transport, storage and also in electron transport. The concentration of Fe(III) in biological systems has to be efficiently balanced as both its deficiency and excess can cause various biological disorders. Also iron is a vital element in environment systems as well as industries. The same iron limit-importance holds for environmental systems, such as fresh and seawaters, in which the iron concentration is claimed to be of crucial relevance [1]. It is therefore very important for biological, clinical, environmental and industrial purposes to efficiently detect Fe3+ion. Several methods such as AAS, ICP-MS have been reported for the determination of iron. However, these methods suffer from being time consuming as they involve multiple sample manipulations, instability if a large number of samples analysis is needed, and high cost. Fabrication of new ion selective electrochemical and optical electrodes with high selectivity and sensitivity, wide linear concentration range, long lifetime, good reproducibility and low cost has been always of a great interest to the scientists. In this work, we have successfully designed a nanostructured electrochemical ion-selective sensor by anchoring the Desferal ion-receptors onto the surface of TiO2/FTO glass substrates, and applied these frameworks as iron-selective electrodes. These analytical devices based on nanostructured titanium dioxide were highly sensitive due to the large surface-to-volume ratio of the nanostructure, and additionally showed excellent selectivity as they did not have the disadvantages of the above-mentioned iron-determination methods. The first component of the proposed potentiometric sensor is the working electrode. TiO2/FTO glass substrates were chosen as the working electrode materials. The TiO2 film was prepared following a standard method described elsewhere [2]. The morphology of the TiO2 films was investigated by scanning electron microscopy (SEM) to assure that the TiO2 particles formed a homogenous porous film and to monitor film thickness. The TiO2/FTO substrates were subsequently modified with the ionophore of interest (desferal) and the potentials of the varying concentration solutions of Fe (III) were read form the voltmeter upon increasing the concentration of the test solutions. Our results demonstrated that the proposed potentiometric sensors exhibit a Nernstian response for Fe (III) ions over a wide concentration range (1.0×10-1 M to 1.0×10-7 M). They also showed a fast response time (=< 1 min), and their potential response remained unaffected of PH in a wide range (2.5-7.2). Moreover, the performance of the sensors was studied in terms of stability, response time, and possible interferences from other ions. For the latter studies, potentiometric selectivity coefficients were determined by the Matched Potential Method (MPM) for the alkali, transition metal and other heavy metal ions as interfering ions. According to our results, the interfering ions could not disturb the functioning of the proposed sensor electrodes significantly, indicating negligible interference in the performance of the nanostructured sensor assemblies. The second component of the designed ion-selective potentiometric sensors is the ionophore or the ion receptor. In this work Desferal was used as the ionophore, which was responsible for complexation with Fe (III) ions, and therefore producing a signal (voltage). Self-assembled monolayers (SAMs) being chemisorbed in an ordered manner on surfaces such as metal-oxides (TiO2), provide a unique way to alter the properties of a surface at will. We have introduced a new method to increase the immobilization of the Desferal ionophores onto the TiO2 electrodes using self-assembled monolayers (SAMs) of phosphonic acids with different alkyl chain-lengths. These alkylphosphonate SAMs covalently bind to the surface of TiO2 from their head groups; the chemical anchoring of the alkylphosphonates to TiO2is then characterized by several changes in the FTIR spectrum. The surface modifications were performed with the aim of increasing the stability as well as the life time of our fabricated nano-sensors. The fabricated iron-selective nanosensors are to be tested for the analysis of some water samples and food materials for the determination Fe (III) ions. The designed TiO2-based nanosensors offered simplicity, rapidity, and reliability as an analytical tool.

Determination of Thallium(I) by Hybrid Mesoporous Silica (SBA-15) Modified Electrode

Chemically modified mesoporous silica material (SBA-15) was used for the construction of Tl(I) selective carbon paste electrode. The best response was found with the electrode containing 10% modifier as electrode material. The electrode has a lower detection limit of 6.0 × 10−9 M in a working concentration range of 1.0 × 10−8–1.0 × 10−1 M. The selectivity coefficient calculated by match potential method (MPM) shows the high selectivity of electrode towards Tl(I) over other tested ions. The electrode was successfully applied as an indicator electrode for the titration of 0.01 M TlNO3solution with standards EDTA solution and for sequential titration of mixture of different anions.