Carboxylated Poly Vinyl Chloride Research Articles

First insight into microplastic groundwater pollution in Latin America: the case of a coastal aquifer in Northwest Mexico

Microplastics have been studied on biota and other environmental domains, such as soils. Despite the importance of groundwater as a resource for millions of people worldwide as drinking water and personal hygiene, domestic, agricultural, mining, and industrial purposes, there are very few studies concerning microplastics in this domain around the world. We present the first study in Latin America addressing this topic. Six capped boreholes were analyzed in terms of abundance, concentration, and chemical characterization, at three different depths, from a coastal aquifer in Northwest Mexico. This aquifer is highly permeable and affected by anthropogenic activities. A total of 330 microplastics were found in the eighteen samples. In terms of concentration, the interval ranged from 10 to 34 particles/L, with an average of 18.3 particles/L. Four synthetic polymers were identified: isotactic polypropylene (iPP), hydroxyethylcellulose (HEC), carboxylated polyvinyl chloride (PVC), and low-density polyethylene (LDPE); with iPP being the most abundant (55.8%) in each borehole. Agriculture activities and septic outflows are considered the potential regional sources of these contaminants into the aquifer. Three possible transport pathways to the aquifer are suggested: (1) marine intrusion, (2) marsh intrusion, and (3) infiltration through the soil. More research about the occurrence, concentration, and distribution of the different kinds of microplastics in groundwater is needed to have a better understanding of the behavior and health risks to organisms, including human beings.

Bioelectronic tongue dedicated to the analysis of milk using enzymes linked to carboxylated-PVC membranes modified with gold nanoparticles

Bioelectronic tongues (bioET) made of sensors combining enzymes and nanomaterials have been shown to be advantageous due to the specificity offered by the biosensors and the enhanced sensitivity provided by the nanomaterials. In this work, an innovative bioET for milk analysis is developed using potentiometric biosensors based on lactic dehydrogenase, galactose oxidase and urease specific for the detection of compounds of interest in milk (lactic acid, galactose and urea). The performance of the biosensors has been fostered by covalently immobilizing the enzymes on membranes of carboxylated polyvinyl chloride combined with gold nanoparticles. The design and composition of the biosensors contributes to preserving the enzymatic activity, allowing limits of detection in the range of 10 −5 – 10 −6 M with excellent sensitivity and reproducibility (variation coefficients ranged from 1 to 5.1%). The three biosensors, combined in a single device and coupled to a pattern recognition software, can discriminate efficiently twelve classes of milk with different fat content (skimmed, semi-skimmed and whole milk) and nutritional characteristics (calcium enriched, lactose free and folic acid-enriched). The bioET shows an excellent classification capability with an accuracy of up to 99.7%. By applying Support Vector Machine (SVM) analysis, the BioET can perform the simultaneous assessment of eight physicochemical parameters (acidity, fat, proteins, lactose, density, urea, dry matter and nonfat dry matter) with satisfactory correlation coefficients and low residual errors. The results are further improved by implementing ensemble methodologies. The proposed strategy has been demonstrated to be useful for improving the performance of bioETs in the dairy industry. • A potentiometric bioET specifically dedicated to milk analysis was developed. • Enzymes were covalently linked to membranes combining Carboxilated-PVC and AuNPs. • The effective enzymatic immobilization helped to retain the enzymatic activity. • Using SVM and ensemble methods, nine physicochemical parameters can be determined simultaneously.

Use of Cucurbit[6]uril as Ionophore in Ion Selective Electrodes for Etilefrine Determination in Pharmaceuticals

AbstractCucurbiturils are macrocyclic molecules and have been used with promising results in the development of electrochemical sensors and biosensors due to their main properties such as shape, selectivity, binding interactions and solubility. However, its application for the development of ion selective electrodes has been scarce. In this work, cucurbit[6]uril was used as molecular‐recognition compound for etilefrine sensing membrane with potentiometric transduction. The etilefrine selective electrode was evaluated and proposed as an alternative methodology for pharmaceutical quality control. Different membranes composition were evaluated, considering the use of different solvent mediators and the presence of anionic additives. The best membrane comprises 9.24 mmol.Kg−1 of cucurbit[6]uril, 68.90 % (w/w) of dibutylsebacate and 30.18 % (w/w) of carboxylated polyvinyl chloride. The electrode exhibited selective cationic response toward the etilefrine in a concentration interval of more than four decades, with an slope of 57.4±0.5 mV dec−1, a practical detection limit of (8±1)×10−7 mol L−1 and a low limit of linear range of (1.25±0.28)×10−6 mol L−1. The selectivity of the electrode towards different interfering was high. A comparative evaluation of the accuracy and precision of both procedures was done using the t‐student test (t4,12=1.135) and the Fischer test (F12,4=2.42) and compared with the tabulated ones (t4,12=1.135, F11,3=5.91) for the level of confidence of 95 %.

Development of urea biosensor using non-covalent complexes of urease with aldehyde derivative of PEG and analysis on serum samples

Non-covalent complexes of urease/polyethylene glycol (PEG)-aldehyde were synthesized using regular molar ratios of urease and PEG-aldehyde at room temperature. The physical properties of the non-covalent complexes were analyzed in order to investigate the impact of coupling ratio, temperature, pH, storage stability, and thermal stability. Urease activity was analyzed by UV–Vis spectrophotometer at 630 nm. The results showed that the strongest thermal resistance was obtained using nU/nPEG:1/1 (mg/mL) complex within all molar ratios tested. The enzymatic activity of nU/nPEG:1/1 complex doubled the activity of the free enzyme. Therefore, this complex was chosen to be used in the analyses. When coupled with PEG-aldehyde, urease exhibited improved activity between pH 4.0–9.0 and the optimum pH was found to be 7.0. The thermal inactivation results of the complex demonstrated that higher activity remained (40%) when compared with the free enzyme (10%) at 60 °C. The storage stability of the non-covalent complex was 4 weeks which was greater than the storage stability of the free enzyme. A kinetic model was suggested in order to reveal the mechanism of enzymatic conversion. Potentiometric urea biosensor was prepared using two different membranes: carboxylated poly vinyl chloride (PVC) and palmitic acid containing PVC. The potentiometric responses of both sensors were tested against pH and temperature and the best results were obtained at pH 7.0 and 20–30 °C. Also, selectivity of the suggested biosensors toward Na+, Li+ Ca2+, and K+ ions was evaluated and the reproducibility responses of the urea biosensors were measured with acceptable results.

Electrochemical sensor based on molecularly imprinted polymer for sensitive triclosan detection in wastewater and mineral water

Triclosan (TCS) is a topical antiseptic widely used in different cosmetic products. It is also a common additive in many antimicrobial household consumables. Over a certain concentration, it becomes risky for human and environmental health. This work describes the development of an electrochemical sensor based on molecularly imprinted polymer (MIP), assembled on screen-printed gold electrode (Au-SPE), dedicated to the TCS detection in environmental water sources. To achieve this goal, an acrylamide/bisacrylamide solution was polymerized after linking TCS with the carboxylic polyvinyl chloride (PVC-COOH) layer onto the Au-SPE. The sensor device fabrication and its retention capabilities were characterized through cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. As control experiment, negligible responses were obtained during the non-imprinted polymer (NIP) test. The sensor could effectively detect TCS avoiding interferences of structural similar substances like 2,4,6-trichlorophenol and catechol. Under optimal conditions, the sensor responses were found logarithmic in the concentration range from 0.1 to 1000 pg mL−1. Indeed, compared with reported works, this sensor exhibits lower detection limit (LOD) and quantification limit (LOQ) of 0.23 and 0.78 pg mL−1, respectively. The developed sensor was effectively applied to wastewater samples for TCS detection and displayed satisfactory performances. Moreover, the different wastewater samples, regarding their TCS contents, were correctly classified by using principal component analysis (PCA) technique. Correspondingly, this work has demonstrated a cheap, simple and effective sensing platform for TCS detection thus making it a promising tool for future evolution of accurate and reliable environmental analysis.

Development and characterization of an electrochemical biosensor for creatinine detection in human urine based on functional molecularly imprinted polymer

In this work, sensor based on a new molecularly imprinted polymer (MIP) for creatinine (Cre) detection, using screen-printed gold electrodes (Au-SPE), was developed. A carboxylic polyvinyl chloride (PVC-COOH) layer was first deposited on Au-SPE surface. The creatinine molecules were attached to the surface of Au-SPE/PVC-COOH. Afterward, the polymerization of acrylamide and N, N′ methylenebisacrylamid filled vacant spaces around them. The subsequent templates removal left binding sites within the polymer which are capable of selectively recognizing creatinine at different concentrations. To test the sensitivity of this biosensor, the same procedure without creatinine was performed on a gold non-imprinted polymer (Au-SPE/NIP). Their retention and molecular-recognition properties were qualitatively investigated by means of three instrumental techniques: voltammetry (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)), electrochemical impedance spectroscopy (EIS), and UV–Visible spectrophotometry (UV–Vis). The obtained results indicate that the MIP had a specific recognition ability for creatinine, while other structurally related compounds, such as urea or glucose, could not be recognized on the MIP. In addition, the biosensor was tested on volunteers with different creatinine urine levels and seemed a promising tool for screening creatinine in point-of-care. Moreover, Partial Least Square (PLS) analysis was used to obtain a correlation between the predicted creatinine concentrations from voltammetric measurements and concentrations measured by Jaffe's reaction as a reference method. The EIS and DPV biosensor responses show a limit of detection of 0.016ng/mL and 0.081ng/mL, respectively, with a linear range from 0.1ng/mL to 1μg/mL. This study provides a promising strategy to fabricate sensor devices based on MIP with highly selective recognition ability, simplicity of operation, small size and low cost.

Surface Imprinting Approach on Screen Printed Electrodes Coated with Carboxylated PVC for Myoglobin detection with Electrochemical Transduction

A novel surface molecularly-imprinted (MI) material to detect myoglobin (Myo) using gold screen printed electrodes (SPE) was developed. The sensitive detection was carry out by introducing a carboxylic polyvinyl chloride (PVCCOOH) layer on gold SPE surface. Myo was attached to the surface of gold SPE/PVC-COOH and the vacant spaces around it were filled by polymerizing acrylamide and N,N-methylenebisacrylamide (cross-linker). This polymerization was initiated by ammonium persulphate. After removing the template, the obtained material was able to rebind Myo and discriminate it among other interfering species. Various characterization techniques including electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirmed the surface modification. This sensor seemed a promising tool for screening Myo in point-of-care.

Potentiometric Determination of Amlodipine Besilate and Valsartan Using Microsized and Polymeric Matrix Membrane Sensors

Two poly(vinyl chloride) matrix membrane electrodes responsive to some drugs affecting the cardiovascular system, Amlodipine besilate (AM) and Valsartan (VL), were developed, described and characterized. A microsized graphite selective sensor was investigated with dibutylsebacate (DBS) as a plasticizer in a polymeric matrix of carboxylated polyvinyl chloride (PVC-COOH) in case of (sensor 1). This sensor 1 was prepared using 2- hydroxy propyl �-cyclodextrin (2HP �-CD) as an ionophore. While sensor 2 preparation was based on precipitation technique with bathophenanthroline iron (II) as electroactive materials in poly(vinyl chloride) (PVC) matrix. Fast and stable Nernstian responses near 1x10 -5 -1x10 -3 M for the two drugs over the pH range 3-6 and 7-9 for the two sensors, respectively, were obtained. The method was successively applied for the determination of AM and VL in presence of each others, in their pharmaceutical formulations and in human plasma samples. The percentages recoveries for the determination of the drugs by the proposed selective electrodes were 99.78 ±0.382 %, 100.23 ± 0.440 %, for sensors 1 and 2, respectively. Statistical comparison between the results obtained by this method and those obtained by the official method and the reported method of the drugs was done and no significant difference was found.

Microsized Graphite Sensors for Potentiometric Determination of Cyclobenzaprine Hydrochloride in Pure Powder, Tablets, and Plasma

Two cyclobenzaprine hydrochloride (CZ) microsized graphite selective sensors were investigated with dibutylsebacate as a plasticizer in a polymeric matrix of carboxylated polyvinyl chloride (PVC-COOH) in the case of sensor 1, based on the interaction between the drug and the dissociated COOH groups in the PVC-COOH. Sensor 2 was based on the interaction between the drug and ammonium reineckate, which acted as anionic electroactive material in the presence of polyvinyl chloride matrix. The two sensors were constructed by using 2-hydroxy propyl beta-cyclodextrin as an ionophore, which has a significant influence on increasing the membrane sensitivity and selectivity of both sensors. Fast and stable Nernstian responses of 1 x 10(-5) - 1 x 10(-2) and 1 x 10(-4) - 1 x 10(-2) M for the two sensors, respectively, with slopes of 58.6 and 55.5 mV/decade, respectively, over the pH range 2-4 were obtained. The proposed method displayed useful analytical characteristics for determination of CZ in its pure powder form with average recoveries 99.95 +/- 0.23 and 99.61 +/- 0.34% for sensors 1 and 2, respectively, and in plasma with good recoveries. The sensors were also used to determine the intact drug in the presence of its degradate and, thus, could be used as stability-indicating methods. The obtained results by the proposed methods were statistically analyzed and compared with those obtained by the U.S. Pharmacopeia method; no significant difference for either accuracy or precision was observed. Results obtained with the two electrodes revealed their performance characteristics, which were evaluated according to International Union of Pure and Applied Chemistry recommendations.

Cardiac troponin T detection using polymers coated quartz crystal microbalance as a cost-effective immunosensor

Cardiac troponin T (cTnT) detection has been the focus of increased interest due to its role in myocardial infarction diagnosis. In this study, we report a relatively low coat technique to detect cTnT using a quartz crystal microbalance (QCM) sensor. A sensitive detection is achieved by introducing a QCM surface with a carboxylic polyvinyl chloride immobilization layer. The surface morphologies of this polymer film under varied deposition thickness have been investigated by field emission scanning electron microscopy and atomic force microscopy. A cTnT detection result from a modified QCM surface can be obtained within a short response time by a direct detection of the immunoreaction and a direct conversion of mass accumulation into a frequency shift, representing a measurable electrical signal. The relationship between the cTnT concentration and the response current from a QCM sensor shows detectability at the concentration of cTnT as low as 5 ng/ml.

Membrane Electrodes for the Determination of Pyridostigmine Bromide

Two pyridostigmine bromide (PB) selective electrodes were investigated with 2-nitrophenyl octyl ether as a plasticizer in a polymeric matrix of carboxylated polyvinyl chloride (PVC-COOH), based on the interaction between the drug solution and the dissociated COOH groups in the PVC-COOH. One of the sensors was fabricated by using PVC-COOH only as anionic site without incorporation of an ionophore (sensor 1). The second sensor was constructed by using 2-hydroxy propyl beta-cyclodextrin as an ionophore (sensor 2). Linear responses of PB within a concentration range of 10(-3)-10(-2) and 10(-5)-10(-2) M, with slopes of 51.9 +/- 0.31 and 56.7 +/- 0.40 mV/decade over pH range of 5-10 were obtained using sensors 2 and 1, respectively. The proposed method displayed useful analytical characteristics for determination of PB in tablets with average recoveries of 100.22 +/- 0.62, and 100.15 +/- 0.72, and in plasma with average recoveries of 99.14 +/- 1.19 and 99.79 +/- 0.72, for sensors 2 and 1, respectively. The utility of 2-hydroxy propyl beta-cyclodextrin as an ionophore has a significant influence on increasing both membrane sensitivity and selectivity of sensor 2 in comparison with sensor 1. The methods were also used to determine the intact drug in the presence of its degradate, and thus could be used as stability-indicating methods. The results obtained by the proposed procedures were statistically analyzed and compared with those obtained by the U.S. Pharmacopeia method. No significant difference for either accuracy or precision was observed.

Synthesis and characterization of polyaniline–carboxylated PVC composites: Application in development of ammonia sensor

Polyaniline (PAni) and carboxylated polyvinyl chloride (PVC) composites were synthesized and studied for their structural, electrical and electrochemical properties and used as a novel material for development of an ammonia gas sensor. Processible conducting composites were prepared by introducing carboxylated PVC in the PAni matrix under vigorous stirring and sonication conditions. Self-standing films of these electroactive and homogeneous composites were obtained by a solution casting method. A significant improvement in processibility, stability and mechanical property was observed in the composite films having PAni up to 90 wt% of total content. However, the electrical conductivity decreased remarkably as the percentage of PAni decreased in the composites. An optimum composition of the composite having 80 wt% of PAni was used for development of a conductometric sensor for ammonia. A simple and low cost sensor device based on two-probe conductivity measurement was developed for ammonia gas. The sensor device having two parallel Pt wires separated nearly 100 μm was bridged with a PAni–carboxylated PVC composite film by a dip coating method. Ammonia gas was sensed in a closed glass chamber. The sensor was fast enough to detect ammonia gas down to 1 ppm and was reproducible, as the response was recorded after 5 min and 10 min exposure.

Determination of Hydroxyurea in Capsules and Biological Fluids by Ion-Selective Potentiometry and Fluorimetry

Two hydroxyurea selective electrodes were investigated with beta-cyclodextrin used as ionophore and either tetrakis (p-chlorophenyl) borate (electrode 1), or tetrakis [3,4-bis (trifluoromethyl) phenyl] borate (electrode 2), as a fixed anionic site in a polymeric matrix of carboxylated polyvinyl chloride. Linear responses of hydroxyurea within a concentration range of 10(-5)-10(-)3 M with slopes of 51.2 and 58.6 mV/decade with pH 3-6 were obtained by using electrodes 1 and 2, respectively. Two spectrofluorimetric methods involving the formation of drug-AI(III) complex (method 3) and drug-Mg(II) complex (method 4) at pH 5 were also investigated. These complexes emit fluorescence at wavelengths of 380 and 355 nm, after excitation at 305 nm, for AI and Mg complexes, respectively. The calibration graphs were rectilinear from 0.5 to 2.5 microg/mL for the AI complex and 1 to 5 microg/mL for the Mg complex. The 4 proposed methods display useful analytical characteristics for determination of hydroxyurea, with average recoveries of 100.2 +/- 0.83 and 99.4 +/- 1.81% in capsules and 99.7 +/- 0.70 and 99.4 +/- 1.25% in biological fluids for the potentiometric and fluorimetric methods, respectively. Results obtained by the proposed procedures were statistically analyzed and compared with those obtained by the U.S. Pharmacopeial method. The 4 proposed procedures were also used to determine the stability of the drug in the presence of its degradate, hydroxylamine.

Potentiometric Dipyridamole Sensors Based on Lipophilic Ion Pair Complexes and Native Ionic Polymer Membranes

ABSTRACT The construction and general performance characteristics of three novel potentiometric PVC membrane sensors responsive to the dipyridamole cation are described. These sensors are based on the use of the ion -association complexes of dipyridamole cation with tetraphenylborate and Reineckate counter anions as ion exchange sites in a plasticized PVC matrix.A plasticized native polymer (e.g., carboxylated polyvinyl chloride) is also used. These sensor exhibit linear and near- Nernstian response for 1×10−2 - 1×10−6 M dipyridamale with cationic slopes of 53.4 ? 55.1 mv/decade and the working pH range is 2-5. No interference are caused by many inorganic and organic cations due to complete dissolution and high exchange equiliburium of the ion-association electroactive complexes in the membrane phase. Fairly good thermodynamic ionic exchange process at the membrane/drug solution interface and good mechanical and thermal stability are obtained up to 60C. The sensor proved useful for determining dipyridamole in various dosage forms with an average recovery of 98.7% and a means standard deviation of0.6%.

A miniaturized urea sensor based on the integration of both ammonium based urea enzyme field effect transistor and a reference field effect transistor in a single chip

A urea biosensor prepared by covalent binding of urease directly to the surface of an ammonium-sensitive field effect transistor (FET) is described. Nonactin incorporated in carboxylated polyvinyl chloride was used to obtain the sensitive membrane of the ammonium-sensitive FET. The grafting of urease on the polyvinylchloride–COOH membrane surface was performed through carbodiimide coupling. The activity of the immobilized enzyme was spectrometrically controlled through the time-dependent disappearance of the absorbance of NADH at 340 nm. An apparent activity of 50% was found, compared with free enzyme. The sensitivity of the urea enzyme FET is 50 mV/pUrea working in a differential mode of 2 μM to 1 mM, this sensitivity being constant during 15 days. Finally, in order to test the potentialities of the urea biosensor for the environmental applications, the detection of heavy metal ions such as Cu(II) and Hg(II) in solution was performed by measuring the remaining activity of the inhibited enzyme.

Dehydration of glycerine‐water mixtures by pervaporation

AbstractDehydration of glycerine‐water mixtures by pervaporation (PV) was studied with Nafion® (NA), cellulose triacetate (CA), polyimide, carboxylated polyvinyl chloride (CPVC), and polyethersulfone (PES) membranes. PES membrane yielded the highest selectivity (6580) and CPVC membrane yielded the lowest selectivity (1552) at 5% by weight of water in the feed and 30°C. The NA membrane yielded the highest permeation flux (0.2–1.45 kg/m2h) of water over the entire water concentration range. Energy of activation of permeation for water was in the range of 7–15 kJ/mol, being highest for CPVC and lowest for CA. Comparison of PV and vapor liquid equilibrium data showed that the former gave better results, particularly for concentrating glycerine above 90 wt%.

Penicillin enzyme biosensors based on pH membrane electrodes

Several penicillin biosensors obtained by covalent binding of penicillinase directly to the surface of pH detectors are presented. Two types of pH electrodes were used: membranes with tridodecylamine, as hydrogen ionophore, incorporated in carboxylated polyvinyl chloride, and membranes made of aminated polyvinyl chloride without any ionophore. Short response time and high stability characterize all described biosensors. The effects of several parameters on the shape of the calibration curves of the biosensors are discussed.