Polymeric Membrane Sensor Research Articles

Development of a reusable polymeric fluorescence sensor based on acryloyl β-cyclodextrin for the determination of aflatoxin B1 in grain products

AFB1 is a harmful substance that can be found in agricultural products and can seriously affect human health, even in trace amounts. Therefore, monitoring AFB1 levels to ensure food safety and protect public health is crucial. New, highly reliable, selective, and rapid detection methods are needed to achieve this goal. Our work involves the development of a polymeric membrane sensor using radical polymerization that can accurately detect AFB1. Various spectroscopic techniques (Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM)) were used to obtain information about the structural and morphological properties of the prepared sensor. The sensor displayed fluorescence selectively responsive to AFB1 at the excitation wavelength of 376 nm and emission wavelength of 423 nm. The polymeric fluorescence sensor showed good sensitivity and a wide linear range from 9.61 × 10−10 and 9.61 × 10−9 mol/L for AFB1quantification. The limit of detection (LOD) is as low as 3.84 × 10−10 mol/L for AFB1. Other mycotoxins, such as aflatoxin B2 and aflatoxin G1, did not interfere with the sensor’s high selectivity towards AFB1. To test the sensor’s effectiveness in detecting AFB1 in real samples, three different grain samples – peanuts, hazelnut butter, and peanuts with a sauce known to contain AFB1 – were utilized. The results were satisfactory and demonstrated that the sensor can be successfully employed in real samples, with an error range of 0.43 % to 12.10 %.

Investigation of Permeability Against Some Metals with a Functional Thiophene Based Polymeric Membrane Sensor

AbstractThere are many advantages of using membranes in the separation of wastewater, but their uses are limited because they are not reusable due to blockages in the membrane. In this study, alginate‐based poly(ethyl‐methacrylate) (PEMA) polymeric membranes containing previously synthesized IOS, which are known to be selective against Fe3+, were prepared and their permeability against heavy metals such as Cd2+, Co2+, Cu2+, Fe3+, Hg2+ and Pb2+ were investigated. The properties of membranes characterized by UV‐Vis and FT‐IR spectrophotometry, were investigated with analysis techniques such as SEM, contact angle measurements, TG‐DTG, DSC and AFM. As a result of the measurements taken from the UV spectrophotometer of the filtrates passed through various aqueous ion solutions of the membranes as mentioned above, it was concluded that the ion to which the membrane was most selective was the Fe3+ ion. Moreover, it could be said that thanks to the repeated filtration processes the membrane prepared retained some Fe3+ ion in each measurement and could be used many times in the filtration process. Resultantly, it is possible to say that the polymeric Fe3+ membrane sensor produced may be suitable for use when it is necessary to remove Fe3+ ion from a polluted aqueous environment.

Conductive imprinted polymeric interfacially modified electrochemical sensors based on covalently bonded layer-by-layer assembly of Gr/Au with flower-like morphology for sensitive detection of 2,4,6-TCP.

Polymeric membrane sensors based on molecular imprinted polymers (MIPs) have been attractive analytical tools for detecting organic species. However, the MIPs in electrochemical sensors developed so far are usually prepared by in situ polymerization of pre-polymers and non-covalent adsorption on the surface of the working electrode. Meanwhile, the MIPs in the electrochemical sensors developed are typically made of a non-conductive polymer film. This results in a relatively low current due to the lack of electron transfer. Additionally, the smoothness of the traditional electrochemical substrate results in a low specific surface area, which reduces the sensitivity of the electrochemical sensor. Here, we describe a novel electrochemical sensor with a conductive interface and MIPs modification. The electrochemical sensor was modified by covalent coupled layer by layer self-assembly with the imprinted polymer film. The incorporation of these two conductive functional materials improves the conductivity of the electrodes and provides interface support materials to obtain high specific surface area. By using 2,4,6-trichlorophenol as the model, the sensitivity of the developed conductive sensor was greatly improved compared to that of the traditional MIPs sensor. We believe that the proposed MIPs-based sensing strategy provides a general and convenient method for making sensitive and selective electrochemical sensors.

A Novel Polymeric Membrane Sensor for Chlorhexidine Determination

In the present work, potentiometric sensors with polymer membranes used for chlorhexidine (CHXD) determination were developed. The polymer membranes were plasticized with bis(2-ethylheksyl)sebacate (DOS) or 2-nitrophenyloctyl ether (o-NPOE). The active compounds used in the membrane were cyclodextrins, crown ethers, and ion exchangers. The best-constructed electrode was based on neutral heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin with lipophilic salt (KTpClBP)—potassium tetrakis(4-chlorophenyl) borate—dissolved in plasticizer, DOS. The presented electrode is characterized by an average cationic slope of 30.9 ± 2.9 mV decade−1 within a linear range of 1 × 10−6 to 1 × 10−3 mol × L−1, while the value of the correlation coefficient is 0.9970 ± 0.0026. The response time was about 5 s when increasing the sample concentration and about 10 s when diluting the sample. The electrode potential is independent of the pH within a range of 4.0–9.5. The polymeric membrane sensor was successfully applied for assays of chlorhexidine digluconate in pure samples and pharmaceutical samples. The relative error from three replicate measurements was determined to be 1.1%. and the accuracy was RSD = 0.3–1.1%.

Predicting the Potentiometric Sensitivity of Membrane Sensors Based on Modified Diphenylphosphoryl Acetamide Ionophores with QSPR Modeling.

While potentiometric, plasticized membrane sensors are known as convenient, portable and inexpensive analytical instruments, their development is time- and resource-consuming, with a poorly predictable outcome. In this study, we investigated the applicability of the QSPR (quantitative structure–property relationship) method for predicting the potentiometric sensitivity of plasticized polymeric membrane sensors, using the ionophore chemical structure as model input. The QSPR model was based on the literature data on sensitivity, from previously studied, structurally similar ionophores, and it has shown reasonably good metrics in relating ionophore structures to their sensitivities towards Cu2+, Cd2+ and Pb2+. The model predictions for four newly synthesized diphenylphosphoryl acetamide ionophores were compared with real potentiometric experimental data for these ionophores, and satisfactory agreement was observed, implying the validity of the proposed approach.

A novel polymeric fluorescence sensor based on acrylated citric acid for detection of melamine adulteration: Application in milk powder

Melamine selective acrylate citric acid (ACA) based polymeric membrane sensor was prepared by radical polymerization method and the sensor was characterized. The sensor showed a selective fluorescent response to melamine (λex/λem = 388/425 nm). The sensor response is linear in the concentration range of 3.96 × 10−9 to 7.93 × 10−8 mol L−1, the optimum pH value is 6.0 and response time is less than 1 min. Limit of detection (LOD) and limit of quantification (LOQ) were calculated as 2.32 × 10−10 mol L−1 and as 7.74 × 10−10 mol L−1, respectively. The sensor showed great selectivity towards melamine in the presence of a large number of molecules and ions. The performance of sensor was also confirmed by determining of melamine in milk powder sample and the results were compared with HPLC results and acceptable results were obtained. As a conclusion, the results revealed that the proposed sensor is an interesting alternative for melamine determination.

Prediction of Carbonate Selectivity of PVC-Plasticized Sensor Membranes with Newly Synthesized Ionophores through QSPR Modeling

Developing a potentiometric sensor with required target properties is a challenging task. This work explores the potential of quantitative structure-property relationship (QSPR) modeling in the prediction of potentiometric selectivity for plasticized polymeric membrane sensors based on newly synthesized ligands. As a case study, we have addressed sensors with selectivity towards carbonate—an important topic for environmental and biomedical studies. Using the logKsel(HCO3−/Cl−) selectivity data on 40 ionophores available in literature and their substructural molecular fragments as descriptors, we have constructed a QSPR model, which has demonstrated reasonable precision in predicting selectivities for newly synthesized ligands sharing similar molecular fragments with those employed for modeling.

A Novel Terpolymer Membrane-Based Electrode Sensor for Selective Determination of Cd(II) Ions

A new polymeric membrane sensor for Cd(II) ion based on methyl acrylate-acrylonitrile-methyl methacrylate terpolymer as membrane carrier has been synthesized via atom transfer radical polymerization (ATRP) method at 60 ºC. Preliminary investigation with the membrane exhibited promising selectivity for Cd(II) ion with a slope of 32.02 mV/decade and the same could be estimated in the concentration range of 1 × 10-6 − 1 × 10-1 M in the working pH range of 4-6 for up to 90 days. The potentials generated across the membrane were reproducible and the response time was less than one minute. The electrode works well even in a partially non-aqueous media. The effect of surfactant and detergent on the working of Cd(II) selective electrode was also studied. A decrease in potential was observed in the presence of appreciable amount of surfactant and detergent. Addition of plasticisers was found to greatly improve the performance of membrane, best results being obtained with the membrane ratio (NaTPB:TP:TBP::1:100:06), exhibiting a working concentration range of 1 × 10-6 − 1 × 10-1 mol L-1 with a short response time of 10 s. The proposed sensor shows significantly good selectivity toward Cd(II) ion in comparison with some alkali, alkaline earth, transition and heavy metal ions. It was successfully employed as an indicator electrode in potentiometric titration of cadmium(II) ions against EDTA solution.

The Long-Lasting Story of One Sensor Development: From Novel Ionophore Design toward the Sensor Selectivity Modeling and Lifetime Improvement

The metalloporphyrin ligand bearing incorporated anion-exchanger fragment, 5-[4-(3-trimethylammonium)propyloxyphenyl]-10,15,20-triphenylporphyrinate of Co(II) chloride, CoTPP-N, has been tested as anion-selective ionophore in PVC-based solvent polymeric membrane sensors. A plausible sensor working mechanism includes the axial coordination of the target anion on ionophore metal center followed by the formed complex aggregation with the second ionophore molecule through positively charged anion-exchanger fragment. The UV-visible spectroscopic studies in solution have revealed that the analyte concentration increase induces the J-type porphyrin aggregation. Polymeric membranes doped with CoTPP-N showed close to the theoretical Nernstian response toward nitrite ion, preferably coordinated by the ionophore, and were dependent on the presence of additional membrane-active components (lipophilic ionic sites and ionophore) in the membrane phase. The resulting selectivity was a subject of specific interaction and/or steric factors. Moreover, it was demonstrated theoretically and confirmed experimentally that the selection of a proper ratio of ionophore and anionic additive can optimize the sensor selectivity and lifetime.

Polymeric Membrane Sensors for Batch and Flow Injection Potentiometric Determination of Procainamide

Three new potentiometric membrane sensors responsive to procainamide hydrochloride (PR) were constructed and their general performance characteristics were determined. The sensors were constructed from PR ion-association complexes with tetraphenylborate (NaTPB) (1), phosphomolybdic acid (PMA) (2) and phosphotungstic acid (PTA) (3) as exchange sites in a polyvinyl chloride (PVC) matrix. The sensors exhibited stable, rapid and near-Nernstian properties for PR at concentrations of $1\times 10^{{-2 }}$ – $4\times 10^{-6}$ , $1\times 10^{-2}- 5\times 10^{-6}$ , $1\times 10^{-2}$ – $6\times 10^{-6}$ M at 25 °C with cationic slopes of 58 ± 0.5, 57 ± 0.5 and 56 ± 0.5 (mV/decade) for sensor 1, 2 and 3 respectively. The response time of the sensors was 20s in the optimum pH range of 4-8. The sensors were used in steady state and flow injection mode (automated system). Method validation revealed the sensors have high selectivity, low detection limits, long life, wide dynamic ranges as well as high accuracy and precision. Direct determination of 5- $2000~\mu \text{g}$ /ml of PR in solution returned average recoveries of 98.5%, 99.0% and 98.5% and mean relative standard deviations of 1.6%, 1.6% and 1.8% at $200.0~\mu \text{g}$ /ml for sensor 1, 2 and 3 respectively. Further, detection of procainamide in spiked urine exhibited favorable relative standard deviation (1.60-1.76%) and high recovery (98.83-99.26%). The sensors were used as end-point indicators for titration of procainamide with NaTPB.

Self-Sterilizing Polymeric Membrane Sensors Based on 6-Chloroindole Release for Prevention of Marine Biofouling.

A self-sterilizing strategy based on antimicrobial organic agent release is proposed for polymeric membrane sensors to prevent marine biofouling. A solid-contact polymeric membrane calcium ion-selective electrode (Ca2+-ISE) is selected as a model sensor. 6-Cholorindole (6-Cl indole) is utilized as the biocidal agent due to its potential antimicrobial activity and environmental friendliness. The plasticized polymeric membrane doped with 6-Cl indole shows a markedly improved antimicrobial activity against the bacterial cells collected from seawater and effectively prevents the formation of a biofilm on the sensor surface, while displaying response properties (i.e., linear range, selectivity, and response time) similar to those of the undoped membrane. Importantly, the present sensor can preserve an improved antimicrobial activity when kept in the artificial seawater for 45 days, indicating highly stable antibacterial properties of the membrane electrode. Additionally, the 6-Cl indole-doped Ca2+-ISE exhibits no significant loss of analytical performance after exposure to a rather concentrated bacterial suspension (∼109 colony-forming units per mL (CFU mL-1)) for 7 days. The proposed antimicrobial agent release methodology can be extended to develop polymeric membrane-based marine sensors with stable biofouling resistances against bacterial colonization.

Validation of a Novel Potentiometric Method Based on a Polymeric PVC Membrane Sensor Integrated with Tailored Receptors for the Antileukemia Drug Cytarabine.

A simple, rapid and easy method is proposed for the detection of a cytostatic therapeutic drug, cytarabine, in real samples. The method is based on potentiometric transduction using prepared and characterized new ion-selective electrodes for cytarabine. The electrodes were integrated with novel man-tailored imprinted polymers and used as a sensory element for recognition. The electrodes revealed a remarkable potentiometric response for cytarabine over the linearity range 1.0 × 10−6–1.0 × 10−3 M at pH 2.8–4 with a detection limit of 5.5 × 10−7 M. The potentiometric response was near-Nernstian, with average slopes of 52.3 ± 1.2 mV/decade. The effect of lipophilic salts and plasticizer types on the potentiometric response was also examined. The electrodes exhibited an enhanced selectivity towards cytarabine over various foreign common ions. Validation and verification of the presented assay method are demonstrated by evaluating the method ruggedness and calculating the detection limit, range of linearity, accuracy (trueness), precision, repeatability (within-day) and reproducibility (between-days). The proposed ion-selective electrodes revealed good performance characteristics and possible application of these electrodes for cytarabine monitoring in different matrices. The electrodes are successfully applied to cytarabine determination in spiked biological fluid samples and in pharmaceutical formulations.

A New Fluorescent Sensor for Arsenic(III) Determination in Aqueous Media.

A novel polymeric membrane sensor was developed by using 2-hydroxyethyl acrylate, trimethylolpropane triacrylate, (3-mercaptopropyl)trimethoxysilane, and poly(ethylene glycol)diacrylate for As(III) determination. Various parameters, like the pH, response time, the foreign ions, and concentration effects were investigated for deciding the optimum working conditions of the polymeric sensor. As a result of this investigation, the optimum pH was found to be 2, and the response time was found to be 30 s. The linear range of the sensor was 6.65 × 10-9 - 3.99 × 10-8 mol L-1 (0.50 - 2.99 μg L-1) with a detection limit of 2.33 × 10-9 mol L-1 (0.18 μg L-1). Soy flour and well-water samples were successfully analyzed with the developed sensor. The sensor can be used at least 100 times after regeneration. It could be reused by washing with purified water and showed good stability for 6 months.

Comprehensive experimental and theoretical investigations on chromium (III) trace detection in biological and environmental samples using polymeric membrane sensor

ABSTRACT In the current work, a new highly selective and sensitive sensor based on PVC membrane for accurate trace detection of chromium (III) ions as the environmental contaminant based on 4-Isopropylcalix[4]arene (4-IPC4) was developed. The electrode demonstrated a working range from 1.0 × 10−6 to 1.0 × 10−1 M with 19.45 ± 0.21 mV and 9.0 × 10−7 M of Nernstian slope and detection limit, respectively. The pH of the electrode was independent of the potential response over the range of 3.0 to 5.5. The developed sensor revealed acceptable repeatability for at least three months with fast response time (less than 15 seconds). The impedance changes of the solution/electrode interface were investigated using the EIS technique. The proposed sensor was used successfully for direct detection of Chromium (III) ions in biological and environmental samples and the obtained values validated by AAS and ICP techniques with the recovery values varied from 99.6 to 101.9% for the concentration range of 15.0 to 75.0 ppm. Moreover, the electrode was successfully applied as an indicator electrode for potentiometric titration of Cr3+ cation with standard EDTA solution. The characterisation of the proposed sensor and its selective membrane were carried out using FT-IR, UV-Vis, and SEM techniques. The adsorption energy as an important parameter of trapping has been calculated at B3LYP/3-21G (d) level via using the density functional theory (DFT). The strong interactions were resulted by natural bond orbital (NBO) calculations between lone pair of O with lone pair* of chromium (III) ions which revealed that the charge transfer plays important role in the formation of the complex.

QSPR modeling of potentiometric sensitivity towards heavy metal ions for polymeric membrane sensors

Potentiometric electrodes with plasticized membranes containing various ligands are widely employed as ion-selective sensors and as cross-sensitive sensors in multisensor systems. The design and testing of the appropriate ligands to make the sensors with required properties is a long and tedious process, which is not always successful. The concept of quantitative structure-property relationship (QSPR) seems to be an attractive complement to the ordinary ligand testing and design in potentiometric sensing. In this study we explore the feasibility of QSPR as a tool for in silico prediction of sensor performance of various ligands in PVC-plasticized potentiometric sensor membranes. The data on potentiometric sensitivity towards Cu2+, Zn2+, Cd2+, Pb2+ of membranes based on 35 nitrogen-containing ligands were employed for QSPR modeling. In spite of the limited dataset the derived models relating the chemical structures of the ligands with their electrochemical sensitivities have reasonable precision of sensitivity prediction with root mean squared errors RMSE around 5 mV/dec and squared determination coefficient R2det about 0.8 in external 10-fold cross-validation for zinc, cadmium and lead. This shows a good promise for further research in this area.

UV photocrosslinked polymeric fluorescent sensor for bisphenol A

Bisphenol A (BPA) is known as endocrine disrupting compound and it is widely used as an intermediate in manufacturing of polycarbonate and epoxy resins. These resins are used to manufacture inner surface of food cans or directly contact with food and can release BPA into food. It is known that BPA poses health risk, but how risky is a matter of debate. In this study, selective and sensitive fluorescent polymeric membrane sensor for detection of BPA was developed based on fluorescence quenching (λex/λem = 272/295 nm). Working concentration range was linear between 4.4 × 10−9 mol L−1 and 1.1 × 10−7 mol L−1 with a detection limit of 1.58 × 10−9 mol L−1. Optimization of sensor was done and the sensor exhibited satisfactory results for being used as a fluorescent sensor for determination of BPA. Additionally, the proposed method was successfully applied to plastic food containers real samples. The developed sensor was shown to be more sensitive than other methods currently in use, and was able to provide results in a matter of seconds, opening up the possibility of a rapid tool for BPA detection.

Response characteristics of lead-selective membrane sensors based on a newly synthesized quinoxaline derivatives as neutral carrier ionophores

Novel lead-selective polymeric membrane sensors were prepared based on the use of 2,2′-(quinoxaline-2,3-diyl bis (azanediyl)) dibenzoic acid (sensor I) and N′-(3-chloroquinoxalin-2-yl) nicotinohydrazide (sensor II) as novel synthetic neutral carrier ionophores embedded in a plasticized poly(vinyl chloride) (PVC) matrix. The sensors displayed near-Nernstian cationic slope of 35.3 and 37.18 mV/decade over the concentration range 7.0 × 10−6–1.0 × 10−3 and 4.0 × 10−6–1.0 × 10−3 M at pH 5 with lower detection limits of 4.7 × 10−6 and 1.8 × 10−6 M for sensors (I) and (II), respectively. The influence of anionic additive on the potentiometric responses of the prepared membrane sensors was studied. The selectivity studies showed high selectivity towards Pb(II) ions over large number of other cations for all the proposed sensors. Formal complex formation constants of the ionophores with Pb(II) and a series of interfering cations have been determined in the organic membrane phase. The formal complex formation constants found are in excellent agreement with those determined by potentiometric selectivity measurements. The sensors were subjected to lead assessment in biological fluid samples either in static and flow-through mode of operations. The results obtained agree fairly well with data obtained by atomic absorption spectrometry (AAS).

Novel potentiometric sensors for pyrilamine maleate

The fabrication and electrochemical response characteristics of four novel potentiometric sensors for determination of pyrilamine maleate (PyraH) were described. The sensors include polymeric membrane electrodes (PME1, PME2) and carbon paste electrodes (CPE1, CPE2). The fabricated sensors were based on the ion-pair of pyrilamine with sodium tetraphenylborate (NaTPB) and ammonium reineckate (NH4RN) using dibutyl phthalate (DBP) as plasticizing solvent. The sensors showed linear, stable and near-Nernstian slopes of 56.4 ± 0.4, 54.2 ± 0.2, 58.8 ± 0.3 and 57.9 ± 0.4 mV decade−1 at 25 ± 0.1 °C and detection limits of 2.0 × 10−5, 1.8 × 10−5, 1.0 × 10−5 and 9.5 × 10−6 mol L−1 for PME1, PME2, CPE1 and CPE2 sensors, respectively. The response time was less than 10 and 8 s for polymeric membrane and carbon paste sensors. The proposed sensors displayed good selectivity for pyrilamine with respect to a number of common inorganic and organic species. The thermal temperature coefficients of the investigated sensors were 0.9508, 0.7012, 0.9450 and 0.6497 mV °C−1. Modified carbon paste sensors showed lower detection limits, higher thermal stability and faster response time than those of polymeric membrane sensors. The proposed sensors displayed useful analytical characteristics for determination of pyrilamine in pharmaceutical preparation and biological fluids (Human urine and plasma).

Polymeric Membrane Sensors for the Selective Determination of Metoclopramide Hydrochloride and their Applications to Pharmaceutical Analysis

Metoclopramide (MCP) ion selective electrodes based on metoclopramide-phosphotungstic acid (MCP-PT) ion pair complex in PVC matrix membrane were constructed. The plasticizers used were tri-butyl phosphate (TBP), di-octyl phenyl phosphonate (DOPP), di-butyl phthalate (DBPH), di-octyl phthalate (DOP), di-butyl phosphate (DBP), bis 2-ethyl hexyl phosphate (BEHP). The sensors based on TBP, DOPP, DBPH and DOP display a fast, stable and linear response with slopes 59.9, 57.7, 57.4, 55.3 mV/decade respectively at pH ranged 2-6. The linear concentration range between 1.0×10-5 – 1.0×10-2 M with detection limit 3.0×10-6 and 4.0×10-6 M for electrodes using TBP, DOPP and DBPH while electrode using DOP shows a linear concentration range between 3.0×10-5 – 1.0×10-2 M and detection limit 6×10-6 M. The selectivity coefficient values were calculated for MCP with respect to different inorganic cations, sugars and amino acids using the MCP depending on TBP plasticizer which is also used for the determination of MCP in pure solutions and in pharmaceutical preparations by direct, standard addition methods and as an indicator electrode in potentiometric titration with phosphotungstic acid (PT) giving satisfactory results.
 Key words: Metoclopramide-HCl membrane sensors , Metoclopramide determination , pharmaceutical analysis , PVC membrane sensors

Automatic potentiometric system for quantification of three imidazole derivatives based on new polymeric PVC membrane sensors

New potentiometric monitoring devices for trace and fast determination of three imidazole derivatives were presented. The sensing materials were fabricated by the inclusion of imidazolinium phosphomolybdate (Imd/PMA) (sensor I), imidazolinium tetraphenylborate (Imd/TPB) (sensor II), or dibenzo-24-crown-8 (DB24C8) (sensor III) in the plasticized polyvinyl chloride (PVC) matrix. The sensors showed clear enhanced response towards imidazolium [Imd+] ions over the concentration range 4.0 × 10−6–1 × 10−2 mol L−1 at pH 5 with 0.42 μg mL−1 as a detection limit. The selectivity was tested with various inorganic and nitrogenous organic ions. Long life span, fast response, long-term stability, and high reproducibility are shown for the sensors. Method validation for the proposed method was achieved by quantifying the detection limit, linear range, accuracy, precision, repeatability, and between-day variability. It revealed good performance characteristics of the proposed sensors. The applicability of the sensors for analyzing imidazole in urine samples was successfully demonstrated via recovery studies.