Screen-printed Ion-selective Electrodes Research Articles

Formulation of Saxagliptin Oral Films: Optimization, Physicochemical Characterization, In-Vivo Assessment, and In-Vitro Real-Time Release Monitoring via a Novel Polyaniline Nanoparticles-Based Solid-Contact Screen Printed Ion-Selective Electrode

Oral dispersible films have received broad interest due to fast drug absorption and no first-path metabolism, leading to high bioavailability and better patient compliance. Saxagliptin (SXG) is an antidiabetic drug that undergoes first-path metabolism, resulting in a less active metabolite, so the development of SXG oral dispersible films (SXG-ODFs) improves SXG bioavailability. The formula optimisation included a response surface experimental design and the impact of three formulation factors, the type and concentration of polymer and plasticiser concentration on in-vitro disintegration time and folding endurance. Two optimised SXG-ODFs prepared using either polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose were investigated. SXG-ODFs prepared with PVA demonstrated a superior rapid disintegration time, ranging from 17 to 890 s, with the fastest disintegration time recorded at 17 s. These short durations can be attributed to the hydrophilic nature of PVA, facilitating rapid hydration and disintegration upon contact with saliva. Additionally, PVA-based films displayed remarkable folding endurance, surpassing 200 folds without rupture, indicating flexibility and stability. The high tensile strength of PVA-based films further underscores their robust mechanical properties, with tensile strength values reaching up to 4.53 MPa. SXG exhibits a UV absorption wavelength of around 212 nm, posing challenges for traditional quantitative spectrophotometric analysis, so a polyaniline nanoparticles-based solid-contact screen-printed ion-selective electrode (SP-ISE) was employed for the determination of SXG release profile effectively in comparison to HPLC. SP-ISE showed a better real-time release profile of SXG-ODFs, and the optimised formula showed lower blood glucose levels than commercial tablets.Graphical

Cost-effective synthesis of MIL-101(Cr) from recyclable wastes and composite with polyaniline as an ion-to-electron transducer for potentiometric Pb2+ sensing

Fabricating an ion-to-electron transducer (IET) from waste in the solid contact screen-printed ion-selective electrodes (SC-SP-ISEs) technique is challenging because its properties determine the potential stability and reproducibility of the designed sensors. Herein, we fabricated an IET substrate from recyclable wastes, and we applied it as an IET layer in an ISE-based sensor for fast and on-site detection of lead ions (Pb2+) in an environmental sample. First, MIL-101(Cr) was prepared based on a combination of PET and Cr+6 waste recycling (R-MIL-101(Cr)). Polyaniline (PANI) was polymerized over R-MIL-101(Cr) to prepare a conductive PANI@R-MIL-101(Cr) composite. Then, it was applied as an IET substrate in the construction of pb2+-ISE for the detection of Pb2+ ions in sediment samples collected from Lake Idku, Egypt. Three Pb2+ sensors were fabricated and abbreviated as sensors I, II, and III corresponded to PANI, R-MIL-101(Cr), and PANI@R-MIL-101(Cr) as IET substrates, respectively. The performance of the sensors was studied to be applied for fast and selective detection of Pb2+ at low concentration levels. Among the fabricated sensors, PANI@R-MIL-101(Cr) shows fast response (5 sec), low detection limit (1 × 10−7 mol/L), and long lifetime reaches 70 days with a potential drift of 0.9 mV h−1. The electrochemical characteristics prove the fast ion-to-electron transportation in the case of PANI@R-MIL-101(Cr) owing to its lower impedance and high capacitance. In-situ polymerization of PANI significantly enhanced the conductivity of the PANI@R-MIL-101(Cr) composite. The hydrophobic nature of PANI@R-MIL-101(Cr) ensures high stability by preventing the formation of water layers at the electrode/membrane interface. These results show the great potential of the IET-based PANI@R-MIL-101(Cr) layer for Pb2 + sensing in environmental samples with low detection limits and high stability for the future development of SC-ISEs.

Application of superhydrophobic Ti3C2 Mxene-based screen-printed ion-selective electrode for determination of Ca2+ concentration

Ti3C2 Mxene is a remarkable electrochemical material owing to its high conductivity, large specific surface area, and high electrical capacity. It can be applied in all-solid-state ion-selective electrodes to improve the ion-electron conversion efficiency and reduce the resistance. However, Ti3C2 Mxene is hydrophilic, which will form a water layer between the ion-selective membrane and the substrate, resulting in response potential drift. In this study, Ti3C2 Mxene functionalized with octadecyltrichlorosilane was developed as the ion-electron conversion layer (solid contact layer), and a polymer membrane containing N, N, N', N' -Tetracyclohexyl-3-oxapentanediamide was used as the Ca2+ selective membrane on a screen-printed electrode substrate. An all-solid Ca2+-selective electrode (SPE/SH-Ti3C2/Ca-ISM) was prepared. The results from cyclic voltammetry and electrochemical impedance spectroscopy proved the high capacitance and fast charge transfer ability of the Ti3C2 Mxene modified electrode. In addition, it shows good performance in the water layer test and anti-interference test and improves the response speed and stability of potential. The linear response range of this disposable screen-printed electrode to Ca2+ is 10−6∼10−1 M, the detection limit is 10−6.2 M, and the response time is about 15 s. The electrode can accurately and quickly determine the level of Ca2+ in serum samples of dairy cows.

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.

Effect of Sodium Gluconate on Decreasing Elevated Nasal Calcium and Improving Olfactory Function Post COVID-19 Infection.

BackgroundCOVID-19 has been associated with temporary olfactory dysfunction in many infected patients. Calcium plays a great role in the olfaction process with negative feedback for the olfaction transmission. Many reports demonstrated calcium elevation in the nasal secretions with a negative effect on olfaction. Sodium gluconate is a water-soluble salt with a chemical structure that lends to act as a highly efficient chelating agent. It can bind the elevated calcium in the nasal secretions reducing the adverse effects on olfactory function.ObjectiveTo evaluate the impact of intranasal sodium gluconate on decreasing the rise of nasal calcium and improving the sense of smell in patients with olfactory dysfunction post-COVID-19 infection.MethodsFifty patients with a history of confirmed COVID-19 suffering from olfactory dysfunction persisted more than 90 days after severe acute respiratory syndrome-coronavirus-2 negative testing were included in a prospective randomized blinded controlled clinical trial. Patients were divided into 2 equal groups, receiving either 0.9% sodium chloride or 1% sodium gluconate. Olfactory function was assessed before treatment and 1 month later using the Sniffin’ Sticks test. Quantitative analysis of the nasal calcium concentration was performed before treatment and 1 month later using a laboratory-designed screen-printed ion-selective electrode.ResultsAfter using sodium gluconate, the measured olfactory scores indicated a clinical improvement from anosmia to hyposmia compared to the nonimprovement sodium chloride receiving group. Also, a remarked decrease in the calcium nasal concentration was observed after using sodium gluconate compared to sodium chloride.ConclusionBased on the proposed results, sodium gluconate may associate with an improvement of the olfactory dysfunction post-COVID-19 infection.

Electroanalytical determination of Al(III) ion in petroleum water samples using symmetric 1,3-diamine-based Schiff base as a carrier

The capacity of a synthetic (N1E, N3E)-N1,N3-bis(quinolin-2-ylmethylene)benzene-1,3-diamine Schiff base ligand to operate as a cation carrier in a poly(vinylchloride) (PVC) membrane (electrode I) and screen-printed ion-selective electrode (SPE) (electrode II) was investigated. The screen-printed and the fabricated poly(vinylchloride) membrane (PVC) electrodes displayed outstanding response properties for Al(III) ions. The electrodes had linear potential response with a slope of 17.95 ± 0.14 and 19.80 ± 0.46 mV decade−1 in the concentration range of 1.0 × 10−5–1.0 × 10−1 and 1.0 × 10−7–1.0 × 10−1 mol L−1 for electrode I and electrode II, respectively. The detection limit of the proposed sensors is 2.1 × 10−6 and 6.3 × 10−8 mol L−1, and it can be used over a period of 35 and 190 days for electrode I and electrode II, respectively. The suggested sensors showed strong selectivity against a wide range of other cations, including alkali, alkaline earth, heavy, and transition metals, and could be employed in pH ranges of 3.0–6.0 and 2.5–6.5 for electrode I and electrode II, respectively. The effect of several plasticizers has been studied. These electrodes had been successfully used to determine Al(III) in aqueous solution and various real water samples. They used as an indicator electrodes in aluminum ion potentiometric titration against standard EDTA solution. The devised approach was used to determine the concentration of Al(III) in several real water samples with high percentage recoveries and low standard and relative standard deviation values. The results were in good agreement with those obtained using atomic absorption spectrometry as indicated from the calculated t- and F-test values.

Widening the applications of the Just-Dip-It approach: a solid contact screen-printed ion-selective electrode for the real-time assessment of pharmaceutical dissolution testing in comparison to off-line HPLC analysis.

Over past years, the field of pharmaceutical dissolution testing has significantly expanded to cover not only the quality control of dosage forms, but also to play an important role in the bioavailability testing paradigm and screening of most formulations. These tests usually need a very long time sampling and monitoring, so that the automation of sampling is laborsaving. Problems often occur with these automatic devices due to sampling lines that may disconnect, crimp, carry over, become mixed up, or are inadequately cleaned. Potentiometric sensors, such as liquid contact (LC-ISE) or solid contact ion-selective electrodes (SC-SP-ISE), can provide timely data to be used for the real-time tracking of the amount of active pharmaceutical ingredients (APIs) released in the dissolution medium without these problems. In this work, we adopted the Just-Dip-It approach as a process analytical technology solution with the ultimate goal of advancing the ion selective sensors to their most effective use in pharmaceutical analysis. Two sensors were fabricated, the traditional LC-ISE and SC-SP-ISE. The sensing poly-vinyl chloride membranes of two electrodes were prepared using 2-nitrophenyl octyl ether as a plasticizer to soften the membrane, and the reduction in resistance to pioglitazone ions (PIO) permeability was achieved through the incorporation of sodium tetraphenylborate and calix[8]arene as a cationic exchanger salt and inclusion complexing ligand, respectively. Finally, prepared membranes were turned into the flexible perm-selective slices of hydrophobic plastic, which work as a barrier to other compounds, except for the PIO cation in the concentration range of 1 × 10−6 to 1 × 10−2 M and 1 × 10−5 to 1 × 10−2 M for SC-SP-ISE and LC-ISE, respectively. The challenges and opportunities of both sensors in comparison to a developed HPLC method were discussed for the dissolution testing of the combination dosage forms of pioglitazone. Potentiometric methods were validated according to IUPAC guidelines, while HPLC was validated according to ICH guidelines to ensure accuracy and precision.

Screen printed ion selective electrodes based on self-assembled thiol surfactant-gold-nanoparticles for determination of Cu(II) in different water samples

10-(4-(4-(Methylthio)-benzylideneamino)phenoxy)decane-1-thiol (MBPD) thiol surfactant was prepared in satisfactory good yield and characterized using IR, mass and 1H NMR spectroscopy. The fabrication of modified screen-printed (MSPE; electrode VI) and modified gold nanoparticles-screen-printed (GNPs-SPE; electrode X) sensors was the goal of this article. An excellent Nernstian response to Cu(II) ion was exhibited by the electrodes within the concentration range from 8.8 × 10−8 to 1.0 × 10−2 mol L−1 and from 5.3 × 10−10 to 1.0 × 10−2 mol L−1 with a detection limit of 8.8 × 10−8 mol L−1 and 5.3 × 10−10 mol L−1 and a slope of 28.80 ± 0.74 and 30.32 ± 0.18 mV decade−1 over a wide pH range of 3.0–7.0 and 2.0–8.5 for electrodes (VI) and (X), respectively. Electrodes (VI) and (X) had fast response time of 7 and 3 s at 25 °C, respectively. The electrodes showed remarkable selectivity for Cu(II) ion over wide variety of metal ions with selectivity coefficients ranged from −2.36 to −6.81 and from −2.56 to −6.97 for electrode VI and electrode X, respectively. For the determination of Cu(II) ion in different real spiked water samples with satisfactory results, potentiometric electrodes (VI and X) were applied to achieve this purpose. The results obtained using this potentiometric method and those obtained using AAS were in good agreement. The mean recovery, relative standard deviation and limit of quantification values support the reliability and reproducibility of the proposed potentiometric method.

All-Solid-State Disposable Polymeric Ion Selective Electrode for Determination of Milnacipran in Pharmaceutical Dosage Form

Screen printing technology offers a simple and cost-effective methodology for large scale production of electrochemical sensors with high reproducibility. Herein, a novel polymeric all-solid-state screen printed ion selective electrode is developed for determination of milnacipran (MLN) in pharmaceutical formulation. The morphology of the electrode was characterized by Scanning Electron Microscopy (SEM). The electrode response was optimized with regard to the membrane composition, type of the plasticizer and the ion exchanger. Optimal potentiometric response was obtained with a membrane containing milnacipran-phosphomolybdate (MLN-PMA) ion associate as ion exchanger and tricresyl phosphate as a plasticizer. The electrode exhibited a Nernstian response of 57.2±1 mV/decade (n = 3) over the concentration range from $1.0 \times 10^{-5}$ to $1.0 \times 10^{-2}$ M of MLN (r=0.9998) with a detection limit of $2.0 \times 10^{-6}$ M. The electrode showed a fast potentiometric response time ( $\le 10\text{s}$ ) with a high potential stability ( $\Delta \text{E}/\Delta \text{t}~\le 1.3~\mu \text{V}$ /s over 40 min of continuous monitoring). The electrode response is independent of pH in the range from 2.5 to 7.0. The electrode is selective to MLN over common pharmaceutical excipients, inorganic cations and amino acids. The electrode was used for determination of MLN in pharmaceutical dosage form with high accuracy (average recovery = 99.30%) and precision (RSD≤2%, n = 5).

Tailor-Made Specific Recognition of Cyromazine Pesticide Integrated in a Potentiometric Strip Cell for Environmental and Food Analysis.

Screen-printed ion-selective electrodes were designed and characterized for the assessment of cyromazine (CYR) pesticide. A novel approach is to design tailor-made specific recognition sites in polymeric membranes using molecularly imprinted polymers for cyromazine (CR) determination (sensor I). Another sensor (sensor II) is the plasticized PVC membrane incorporating cyromazine/tetraphenyl borate ion association complex. The charge-transfer resistance and water layer reached its minimal by incorporating Polyaniline (PANI) solid-contact ISE. The designed electrodes demonstrated Nernstain response over a linear range 1.0 × 10−2–5.2 × 10−6 and 1.0 × 10−2–5.7 × 10−5 M with a detection limit 2.2 × 10−6 and 8.1 × 10−6 M for sensors I and II, respectively. The obtained slopes were 28.1 ± 2.1 (r2 = 0.9999) and 36.4 ± 1.6 (r2 = 0.9991) mV/decade, respectively. The results showed that the proposed electrodes have a fast and stable response, good reproducibility, and applicability for direct measurement of CYR content in commercial pesticide preparations and soil samples sprayed with CYR pesticide. The results obtained from the proposed method are fairly in accordance with those using the standard official method.

Disposable Multiwall Carbon Nanotubes Based Screen Printed Electrochemical Sensor With Improved Sensitivity for the Assay of Daclatasvir: Hepatitis C Antiviral Drug

Disposable all solid-state screen printed ion selective electrode was developed for the assay of daclatasvir (DCV) in pharmaceutical formulation and spiked human urine. The sensor is based on daclatasvir-tetraphenyl borate (DCV-TPB) as a sensing element. Incorporation of the multiwall carbon nanotubes (MWCNTs) into the ion selective membrane was found to influence the sensor sensitivity. The MWCNTs containing membrane exhibited a Nernstian slope of 31.0±1 mV/decade over a wide concentration range from $1 \times 10^{-5}$ to $1 \times 10^{-2}$ M DCV (r2 = 0.9999) with a LOD of $8.5 \times 10^{-7}$ M in a pH 3.3 compared to a slope of 27.5 ± 1 mV/decade, over the concentration range from $1 \times 10^{-4}$ to $1 \times 10^{-2}$ M DCV for MWCNTs-free ion selective membrane. The response time of the electrode was $\le 0.23~\mu \text{V}$ /min against $330.0~\mu \text{V}$ /min for a coated glassy carbon electrode. Further characterizations, including reproducibility, chronopotentiometry, and selectivity were examined. The electrode showed high selectivity to DCV against the common interfering compounds. The electrode was applied for the assay of daclatasvir in pharmaceutical formulation and spiked urine sample with a high accuracy (±2%) and precision (%RSD <2).

Inline potentiometric monitoring of Butyrylcholinesterase activity based on metabolism of bambuterol at the point of care

Globally, millions of patients are being exposed to anesthetics during surgeries. Butyrylcholinesterase (BChE) is the main metabolizing enzyme for these anesthetics. BChE silent activity defect, either acquired or genetic, may be life threatening due to apnea and respiratory paralysis. Hence, the development of point-of-care analytical methods for screening of BChE activity is of great importance to identify patients with BChE defect. This study describes the development of an ionophore-doped screen-printed ion selective electrode as a fast and simple method to efficiently achieve a continuous monitoring of the enzymatic hydrolysis of bambuterol (BAM) as substrate. BChE activity parameters (Vmax and Km) were calculated to be 1.7 × 10−8 mol min-1 ml-1 and 7.9 × 10-5 mol l-1, respectively, indicating high affinity of BChE towards BAM. A side by side comparison of the results obtained using the inline potentiometric approach and a recently published online ATR-FTIR method is presented to highlight the opportunities and challenges of each method. For clinical diagnostics, this approach provides a new platform for rapid determination of enzyme kinetics in real time and clearly identify patients that are susceptible to potentially lethal respiratory paralysis.

A Battery-Powered Wireless Ion Sensing System Consuming 5.5 nW of Average Power

This paper presents a battery-powered wireless ion sensing platform featuring complete sensing-to-transmission functionality. A 1 mm × 1.2 mm chip fabricated in 65 nm includes a 406 pW potentiometric analog front end, a 780 pW 10-bit SAR ADC, a 2.4 GHz power-oscillator-based wireless transmitter that consumes an average of 2.4 nW during a 10-sample/sec transmission rate, two timing generation oscillators that each consume 140 pW, and a 3:1 switched-capacitor dc-dc converter with 485 pW of quiescent power that achieves the efficiencies of 96.8% and 70.5% at 60 and 3.9 nW loads, respectively. The chip connects to a screen-printed ion-selective electrode responsive to sodium ions, and in vitro testing across an NaCl solution concentration range of 0.1-100 mM exhibited a linear near-Nernstian response with a slope of 71 mV/log10[Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ]. When all blocks are operating, the system consumes an average of 5.5 nW.

Screen Printed Ion Selective Electrodes as a Fully Integrated PAT Tool: Application to the Analysis and Impurity Profiling of Diatrizoate Sodium

Conventional pharmaceutical manufacturing is generally accomplished via batch processing followed by laboratory testing conducted on some representative samples collected to evaluate batch quality. However, today significant opportunities exist for improving pharmaceutical quality assurance through innovation in process development and analysis. FDA's guidance for pharmaceutical industry has defined Process Analytical Technology (PAT) as a system for designing, analyzing, and controlling manufacturing through timely measurements, with the goal of ensuring final product quality. Nevertheless, pharmaceutical companies are encouraged to develop and implement innovative PAT tools for designing, analyzing, and controlling manufacturing through real-time strategies (i.e., during processing) of critical quality attributes of raw and final product. The goal of PAT is that quality cannot be tested into products; it should be built-in or should be by design. Furthermore, FDA stated that sensor-based measurements could pave the way to built-in product quality assurance which is the key to PAT development. From this perspective, this scientific approach presents screen-printed ISEs (SPEs) as a potential real-time analyzer and PAT-tool. Diatrizoate sodium (DTA) was chosen as a model analyte, it is a widely used X-ray contrast agent that is susceptible to degradation into a cytotoxic and mutagenic compound, that can be also used as its precursor. Two SPEs were fabricated and used successfully in the analysis of both DTA and its potential impurity. The proposed SPEs have the advantage of being real-time analyzers that could be fully integrated into the production cycle giving a key to a promising competent PAT-tool.

Modified screen-printed ion selective electrodes for potentiometric determination of sodium dodecylsulfate in different samples.

Fabrication and general performance characteristics of novel screen-printed sensors for potentiometric determination of sodium dodecylsulfate (SDS) are described. The sensors are based on the use of ion-association complexes of SDS with cetylpyridinium chloride (electrode I) and cetyltrimethylammonium bromide (electrode II) as exchange sites in a screen-printed electrode matrix. Electrodes (I) and (II) show fast, stable, and near-Nernstian response for the mono-charge anion of SDS over the concentration range of 1×10(-2) - 5.8×10(-7) and 1×10(-2)-6.3×10(-7) mol/L at 25°C and the pH range of 2.0-9.0 and 2.0-8.0 with anionic slope of 57.32±0.81 and 56.58±0.65 mV/decade, respectively. Electrodes (I) and (II) have lower LODs of 5.8×10(-7) and 6.3×10(-7) mol/L and response times of about 8 and 13 s, respectively. Shelf life of 5 months for both electrodes is adequate. Selectivity coefficients of SDS related to a number of interfering cations, and some inorganic compounds were investigated. There were negligible interferences caused by most of the investigated species. The direct determination of 0.10-13.50 mg of SDS by electrodes (I) and (II) shows average recoveries of 99.96 and 99.85%, and mean RSDs of 0.83 and 1.04%, respectively. In the present investigation, both electrodes were used successfully as end point indicators for determination of SDS in pure pharmaceutical preparations and real spiked water samples. The results obtained using the proposed sensors to determine SDS in solution compared favorably with those obtained by the standard addition method.

A New Screen-printed Ion Selective Electrode for Determination of Citalopram Hydrobromide in Pharmaceutical Formulation

Abstract Novel citalopram screen-printed ion selective electrodes were fabricated, characterized and used for the determination of citalopram in pharmaceutical formulations. The proposed sensors incorporated potassium tetrakis( p -chlorophenyl) borate (KTpClPB) ionophore (electrode V) and citalopram-phosphotungstate (CP-PT) ion pair complex (electrode X) as electroactive materials in screen-printed electrodes and tricresylphosphate (TCP) as solvent mediator. The fabricated electrodes demonstrated near Nernstain response over wide linear range of 4.9 × 10 −7 −1.0 × 10 −2 M and 1.0 × 10 −6 −1.0 × 10 −2 M citalopram with lower limit of detection of 4.9 × 10 −7 M and 1.0 × 10 −6 M and slope of (60.47 ± 0.80) mV decade −1 and (59.93 ± 1.45) mV decade −1 for electrode (V) and (X), respectively. The results showed that the proposed sensors had the characteristics such as fast and stable response, good reproducibility, long term stability (5 and 4 months) and applicability over a wide pH range of 2–9 and 2–8 for electrodes (V) and (X). The sensors displayed good selectivity for citalopram with respect to number of common foreign inorganic, organic species, excipients and the fillers added to the pharmaceutical preparation. The sensors were successfully applied for the determination of citalopram in tablet, urine and serum.

Potentiometric determination of iron in polluted water samples using new modified Fe(III)-screen printed ion selective electrode

This article is focused on the determination of Fe(III) ion as an important factor in water pollution. A potentiometric method based on screen-printed ion-selective electrode was described for the determination of Fe(III) ion in different polluted water samples. It is based on incorporation of the Fe-phosphotungstate ion-associate in a screen-printed electrode (SPE) composition and tricresylphosphate (TCP) as plasticizer. 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 Nernstian response of 19.20±0.73mVdecade−1 in the concentration range of 1×10−7–2.5×10−2molL−1. The electrode was found to be usable within the pH range of 3–7.5 and exhibited a fast response time (about 7s), low detection limit (1.57×10−7molL−1), long lifetime (>6 months) and good stability. The isothermal temperature coefficient (dE0/dt) of the electrode was calculated. The electrode was successfully applied for the determination of Fe(III) ion in pure solutions and polluted water samples (formation, tab and sea water samples) using potentiometric determination technique. The results obtained applying this potentiometric electrode is comparable with those obtained using inductive coupled plasma technique.

Application of Electrochemically Reduced Graphene Oxide on Screen-Printed Ion-Selective Electrode

In this study, a novel disposable all-solid-state ion-selective electrode using graphene as the ion-to-electron transducer was developed. The graphene film was prepared on screen-printed electrode directly from the graphene oxide dispersion by a one-step electrodeposition technique. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to demonstrate the large double layer capacitance and fast charge transfer of the graphene film modified electrode. On the basis of these excellent properties, an all-solid-state calcium ion-selective electrode as the model was constructed using the calcium ion-selective membrane and graphene film modified electrode. The mechanism about the graphene promoting the ion-to-electron transformation was investigated in detail. The disposable electrode exhibited a Nernstian slope (29.1 mV/decade), low detection limit (10(-5.8) M), and fast response time (less than 10 s). With the high hydrophobic character of graphene materials, no water film was formed between the ion-selective membrane and the underlying graphene layer. Further studies revealed that the developed electrode was insensitive to light, oxygen, and redox species. The use of the disposable electrode for real sample analysis obtained satisfactory results, which made it a promising alternative in routine sensing applications.

Septonex–tetraphenylborate screen-printed ion selective electrode for the potentiometric determination of Septonex in pharmaceutical preparations

A screen-printed electrode (SPE) was fabricated for the determination of 1-(ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex) based on the use of Septonex-tetraphenylborate as the electroactive substance, and o-nitrophenyloctylether (o-NPOE) as the plasticizing agent. The electrode passes a near-Nernstian cationic slope of 59.33 ± 0.85 mV from activity between pH values of 2 to 9 with a lower detection limit of 9×10(-7) M and response time of about 5 s and exhibits an adequate shelf-life of 6 months. The method was applied for the determination of Septonex in pharmaceutical preparations. A percentage recovery of 99.88% was obtained with RSD=1.24%. The electrode was successfully applied in the determination of Septonex in laboratory-prepared samples by direct potentiometric, calibration curve and standard addition methods. Potentiometric titration of Septonex with sodium tetraphenylborate and phosphotungstic acid as a titrant was monitored with the modified screen-printed electrode as an end-point indicator electrode. Selectivity coefficients for Septonex relative to a number of potential interfering substances were determined. The sensor was highly selective for Septonex over a large number of compounds. Selectivity coefficient data for some common ions show negligible interference; however, cetyltrimethylammonium bromide and iodide ions interfere significantly. The analytical usefulness of the proposed electrode was evaluated by its application in the determination of Septonex in laboratory-prepared pharmaceutical samples with satisfactory results. The results obtained with the fabricated sensor are comparable with those obtained by the British Pharmacopeia method.

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.