Manufacturing of a New Selective Membrane Electrode for Neomycin Sulfate and its Estimation by Potentiometric Method

The research aims to prepare a new ionic membrane selective electrode for NYM Neomycin based on tungstophosphoric acid (TPA), Poly Vinyl Chloride (PVC) and DPPH (Di-Butyl Phthalate). It was found that the electrode is sensitive to concentrations ranging between (1 x 10-1-1 x 10-5) mol/L, and it gave a Nernstian response of (29.7 mV/decade) and a correlation coefficient (r) of (0.9939). The factors affecting the response of the electrode were studied, as it was found that the best concentration of the internal filling solution was (1 x 10-3) mol/L, and that the best pH range in which the electrode worked was between (3.5-1.5) and the best Nernstian response at pH (pH = 2.5) The effect of temperature was also studied, as it was found that the best temperature was (25°C) and the response time of the electrode was between (20-40) seconds. It was also found that the chronological age of the electrode was (25) days. The selectivity coefficient (Ki,jpot) was calculated in the presence of negative and positively charged interfering ions.

An Ion-Imprinted Imidazole-Functionalized Ordered Mesoporous Silica For Selective Removal of Chromium(VI) From Electroplating Effluents

In this work, ion imprinted technology incorporated with mesoporous silica materials (MCM-41) to obtain the novel specific adsorbent, ion imprinted mesoporous silica. Cr(VI) imprinted mesoporous silica (Cr(VI)IMS) was synthesized and used for adsorption studies and waste water application. A synthesized imidazolyl silane agent act as the functional monomer in the imprinted process to build up highly ordered functionalized imprinted materials. The chemical composition, thermal stability, porosity and highly ordered morphology were characterized by Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance(NMR), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) respectively. The Brunauer-Emmett-Teller (BET) surface area was 1054.51 m2 g-1 in this study. The Cr(VI)IMS showed great adsorption capacity to hexavalent chromium ions in acidic solution up to 45.6 mg g-1. Cr(VI)IMS displayed much higher adsorption capacity to Cr(VI) ions than other negative ions. The relative selectivity coefficient was 2.56, higher than those of other anions (below 1.5). After eight adsorption-regeneration cycles, the adsorption efficiency of Cr(VI)IMS still reached 92.5%. The Cr(VI)IMS was found to exhibit equivalent property after multiple cycles of experiments, indicating good repeatability and reproducibility.

CHLORIDE SENSOR FABRICATION BASED ON SPE Ag/AgCl THROUGH CYCLIC VOLTAMMETRIC TECHNIQUE: SCAN RATE EFFECT

The Cyclic Voltammetric (CV) technique is one of the Ag/AgCl fabrication processes. In electrochemical processes using this CV technique, the microstructure of the surface of a substrate or electrode can affect the scan rate. Thus, this study aims to identify the scan rate effect of the Cl-ion sensor fabrication process using the CV technique on the performance of the Cl-ion sensor. First, the CV process was carried out in one cycle to grow the AgCl layer on the Ag surface. Then, this process was carried out at varied scan rates of 20, 40, 60, 80, and 100 mV/s. After completing the Ag/AgCl fabrication process, it was followed by the characterization process, selectivity coefficient test, lifetime test, and validation test to compare the test results of the Cl SPE Ag/AgCl ion sensor with Ag/AgCl commercial. The results showed that the optimum Cl-ion sensor response was obtained at the scan rate of 60 mV/s. Then, based on the validation test, the Cl-ion in the two samples did not show significant differences. Therefore, it indicates that the SPE Ag/AgCl ion sensor has the same performance as the Ag/AgCl commercial.

The Performance of Organophosphate Pesticides Determination Using Biosensor Based on Small Device Potentiometer as a Transducer

The need to control pesticide residues in foodstuffs in a fast and straightforward analysis for the field scale is required. Therefore, this research develops a transducer-based biosensor with a small device potentiometer (SDP) to produce a fast and accurate pesticide detection tool. The biosensor based on Au electrodes by immobilizing the acetylcholinesterase (AChE) enzyme coated membrane cellulose acetate (CA) 15% (w/v) cross-linked glutaraldehyde (GA) 25% (v/v) and SDP as a transducer that produces a potential value. The biosensor testing results on the organophosphate pesticide class, namely diazinon and profenofos, showed the sensitivity of 21.204 and 20.035 mV decade−1, Limit of Detection (LoD) 10−7 mg L−1, selectivity coefficient −1 < Ki,j < 1 and accuracy of 99.497 and 94.765%, respectively. The results showed that the biosensor connected to an SDP transducer had an excellent performance in determining the presence of organophosphate pesticides.

Selective to lithium ions nanocomposite sorbents based on TiO2 containing manganese spinel

A method for obtaining nanocomposite sorbents, which are selective towards Li+ ions, has been proposed. The samples were based on adsorptive-active anatase, the selective component being lithium-manganese spinel LiMn2O4. This component was synthesized preliminarily, its nanoparticles were added to the sol of insoluble titanium hydroxocomplexes, and the nanocomposite was precipitated from this suspension and calcined at 5000C. A number of sorbents with different molar ratio of Ti:Mn were prepared via this procedure; they were investigated by means of chemical analysis, X-ray diffraction analysis, optical microscopy, transmission electron microscopy and scanning electron microscopy. The size of nanocrystallites was 20–30 nm. An increase in the spinel amount caused a decrease in the sorbent grain size; however, they the sorbent grains were mechanically durable due to TiO2 which was a binder. Adsorption of Li+ from the solution containing an excess of Na+ ions was studied. The optimal amount of LiMn2O4 (13%) was determined. The sample was obtained in the form of rather large grains (0.3 mm) and the selectivity coefficient Li+/Na+ was about 500. The sorbent was regenerated by a 1 M HNO3 solution without manganese leakage. After 10 cycles of sorption-desorption, the concentrate was obtained. This concentrate can be used for Li2CO3 precipitation.

Molecularly Imprinted Magnetic Fluorescent Nanocomposite-Based Sensor for Selective Detection of Lysozyme

A new strategy for the design and construction of molecularly imprinted magnetic fluorescent nanocomposite-based-sensor is proposed. This multifunctional nanocomposite exhibits the necessary optics, magnetism and biocompatibility for use in the selective fluorescence detection of lysozyme. The magnetic fluorescent nanocomposites are prepared by combining carboxyl- functionalized Fe3O4 magnetic nanoparticles with l-cysteine-modified zinc sulfide quantum dots (MNP/QDs). Surface molecular imprinting technology was employed to coat the lysozyme molecularly imprinted polymer (MIP) layer on the MNP/QDs to form a core-shell structure. The molecularly imprinted MNP/QDs (MNP/QD@MIPs) can rapidly separate the target protein and then use fluorescence sensing to detect the protein; this reduces the background interference, and the selectivity and sensitivity of the detection are improved. The molecularly imprinted MNP/QDs sensor presented good linearity over a lysozyme concentration range from 0.2 to 2.0 μM and a detection limit of 4.53 × 10−3 μM for lysozyme. The imprinting factor of the MNP/QD@MIPs was 4.12, and the selectivity coefficient ranged from 3.19 to 3.85. Furthermore, the MNP/QD@MIPs sensor was applied to detect of lysozyme in human urine and egg white samples with recoveries of 95.40–103.33%. Experimental results showed that the prepared MNP/QD@MIPs has potential for selective magnetic separation and fluorescence sensing of target proteins in biological samples.

DMAEMA-grafted cellulose as an imprinted adsorbent for the selective adsorption of 4-nitrophenol

4-Nitrophenol is a highly toxic environmental pollutant. It is a challenge to selectively remove it from a mixture of various pollutants. Herein, we report a study on the selective adsorption of 4-nitrophenol by using molecularly imprinted polymers (MIPs). The imprinted polymer was synthesized using cellulose as a framework, onto which, the complex of the imprinting molecule (i.e., 4-nitrophenol) and a candidate material [namely, 2-(dimethylamino)ethyl methacrylate. DMAEMA] was grafted. The obtained MIP showed an excellent adsorption capacity with good selectivity. Also, the adsorption of 4-nitrophenol by the obtained MIP was fast and the adsorbent exhibited good recyclability. The thermodynamics and kinetics of the adsorption process of 4-nitrophenol by MIP was thoroughly studied, where an otherwise-equivalent non-imprinted polymer was used as a control in the experiments. The selectivity of the MIP adsorbent for 4-niteophenol was evaluated by two types of experiments: (1) adsorption experiments in single-component adsorbate systems (containing 4-nitrophenol, 3-nitrophenol, catechol, or hydroquinone), and (2) competitive adsorption experiments in binary adsorbate systems (containing 4-nitrophenol plus either 3-nitrophenol, catechol or hydroquinone). The selectivity coefficient for 4-nitrophenols was twice of those of other phenols (that were all around 2), indicative of the extent of the affinity of MIPs to these phenolic compounds. The recyclability of the adsorbent was evaluated for 5 adsorption–desorption cycles, where the adsorption capacity of the last cycle remained over 90.2% of that of the first cycle. Graphic Abstract

Synthesis of Graphite Paste/Molecularly Imprinted Polymer (MIP) Electrodes Based on Polyeugenol as a Glucose Sensor with Potentiometric Method

Diabetes mellitus is a chronic disease in which the body is unable to metabolize carbohydrates, fats, and proteins. In this study, eugenol was polymerized and then contacted with glucose and crosslinked using polyethylene glycol diglycidyl ether (PEGDE). The resulted PE-Glucose-PEGDE was eluted using ethanol to form MIP-Glucose. It was then characterized by FTIR, SEM, electrodes using the Eutech 510 potentiostat and UV-Vis spectrophotometer. The result of polyeugenol synthesis is a reddish-brown powder with a yield of 99.90% and a molecular weight of 6318.033 g/mol. UV-Vis spectrophotometer analysis showed that the contacted glucose was 2152.505 ppm. SEM results showed differences in the surface morphology of the material, indicating the formation of cavities in MIP and ESM, while no cavities are found in NIP and ESN. The electrode optimization resulted in the best composition ratio of MIP 1 mol: paraffin: graphite, respectively of 20:35:45. The resulting electrode has a Nernst factor of 20.24 mV/decade with a measurement range of 10–5–10–1 M, a limit of detection value of 8.363 × 10–5 M, and the value of the selectivity coefficient (Kij) of the electrodes in a (10–5–10–1) M fructose solution was 0.3733; 0.23048; 0.17864; 0.12359; 0.1073.

Polyvinyl Chloride Modified Carbon Paste Electrodes for Sensitive Determination of Levofloxacin Drug in Serum, Urine, and Pharmaceutical Formulations

Levofloxacin (LF) is a medically important antibiotic drug that is used to treat a variety of bacterial infections. In this study, three highly sensitive and selective carbon paste electrodes (CPEs) were fabricated for potentiometric determination of the LF drug: (i) CPEs filled with carbon paste (referred to as CPE); (ii) CPE coated (drop-casted) with ion-selective PVC membrane (referred to as C-CPE); (iii) CPE filled with carbon paste modified with a plasticizer (PVC/cyclohexanone) (referenced as P-CPE). The CPE was formulated from graphite (Gr, 44.0%) and reduced graphene oxide (rGO, 3.0%) as the carbon source, tricresyl phosphate (TCP, 47.0%) as the plasticizer; sodium tetrakis[3,5-bis(trifluoromethyl)phenyl] borate (St-TFPMB, 1.0%) as the ion exchanger; and levofloxacinium-tetraphenylborate (LF-TPB, 5.0%) as the lipophilic ion pair. It showed a sub-Nernstian slope of 49.3 mV decade−1 within the LF concentration range 1.0 × 10−2 M to 1.0 × 10−5 M, with a detection limit of 1.0 × 10−5 M. The PVC coated electrode (C-CPE) showed improved sensitivity (in terms of slope, equal to 50.2 mV decade−1) compared to CPEs. After the incorporation of PVC paste on the modified CPE (P-CPE), the sensitivity increased at 53.5 mV decade−1, indicating such improvement. The selectivity coefficient (log KLF2+,Fe+3pot.) against different interfering species (Na+, K+, NH4+, Ca2+, Al3+, Fe3+, Glycine, Glucose, Maltose, Lactose) were significantly improved by one to three orders of magnitudes in the case of C-CPE and P-CPE, compared to CPEs. The modification with the PVC membrane coating significantly improved the response time and solubility of the LF-TPB within the electrode matrix and increased the lifetime. The constructed sensors were successfully applied for LF determination in pharmaceutical preparation (Levoxin® 500 mg), spiked urine, and serum samples with high accuracy and precision.

Construction of a Highly Selective Membrane Sensor for the Determination of Cobalt (II) Ions

A highly Co (II) liquid ion-selective electrode depending on the reaction of cobalt ions with the reagent 2-(5-Bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl) amino] aniline is successfully fabricated. The characteristic slope (56.66 mV), the linear range response from 3.4 × 10−8 to 2.4 × 10−2 molar, the detection limit (2.7 × 10−8) molar, the selectivity coefficient toward some metal ions, the time of response (10 s), lifetime (seven months), the pH effect on the sensor potential and the basic analytical parameters were studied. The sensor was used to estimate the concentration of cobalt ions in food products and pharmaceutical formulations. The obtained results of the developed sensor were statistically analyzed and compared with those of other different reported electrodes.