Development of hybrid MIL-53(Al)@CBS for ternary adsorption of tetracyclines antibiotics in water: Physical interpretation of the adsorption mechanism.

In this study, a hybrid material, MIL-53(Al)@CBS, was synthesized via the solvothermal method, involving the growth of MIL-53(Al) crystals on cocoa bean shell residues (CBS). Physicochemical characterization techniques, including TGA, BET, FTIR, XRD, and SEM, confirmed successful hybridization. MIL-53(Al)@CBS was employed as an adsorbent for antibiotics (oxytetracycline, tetracycline, chlortetracycline) separation from aqueous solutions. Parameters like pH, adsorbent dose, concentration, time, and temperature were systematically evaluated. FTIR revealed π-π interactions and hydrogen bonds between tetracyclines and the adsorbent. MIL-53(Al)@CBS exhibited adsorption, with removal rates up to 98.92%, 99.04%, and 98.24% for OTC, TC, and CTC, respectively. Kinetics suggested adsorption depends on active site availability, with TC adsorbing fastest. Microscopic models showed adsorption on three distinct active site types with different affinities without competition or adherence to the Langmuir hypothesis. Importantly, MIL-53(Al)@CBS maintained high adsorption capacity even after ten washing cycles, highlighting its potential for water treatment.

Application of a novel hybrid MIL-53(Al)@rice husk for the adsorption of glyphosate in water: Characteristics and mechanism of the process.

The development of new materials that have a high capacity to remove pollutants in water-based media is becoming increasingly important because of the serious contamination of water and the negative impact on biodiversity and public health. The presence of glyphosate in water, the most widely used herbicide worldwide, has triggered alerts owing to the collateral effects it may cause on human health. The main objective of the present study was to investigate the potential of the hybrid material MIL-53(Al)@RH for the adsorption of glyphosate in aqueous solution. The material was obtained following the methodology of MIL-53(Al) synthesis in the presence of hydrolyzed rice husk assisted by microwave. Batch adsorption experiments were carried out to evaluate the adsorbent dosage, pH0 solution effect, contact time, adsorbate concentration, and temperature effect. The results demonstrated that a maximum adsorption capacity of 296.95 mg g-1, at pH0 4 with a ratio of 0.04 g MIL-53(Al)@RH/50 mL of solution, was achieved in 30 min. The Avrami and pseudo-second order models appropriately described the adsorption kinetics and the equilibrium by Langmuir and Sips models. The enthalpy changes (ΔH°) determined propose an endothermic reaction governed by chemisorption, corroborating the kinetic and equilibrium settings. Hydrogen bonds, π*-π interactions, and complexation between the metal centers of MIL-53(Al) and the anionic groups of glyphosate were postulated to be involved as adsorption mechanisms. Finally, for practical application, MIL-53(Al)@RH was packed in a column for a fixed-bed test which revealed that the hybrid can remove glyphosate with an adsorption capacity of 76.304 mg L-1, utilizing 90% of the bed.

Development of an inexpensive and rapidly preparable enzymatic pencil graphite biosensor for monitoring of glyphosate in waters.

Glyphosate (GLY) is the most widely used non-selective broad-spectrum herbicide worldwide under well-reported side effects on the environment and human health. That's why it's necessary to control its presence in the environment. This work describes the development of an affordable, simple, and accurate electrochemical biosensor using a pencil graphite electrode as support, a horseradish peroxidase enzyme immobilized on a polysulfone membrane doped with multi-walled carbon nanotubes. The developed electrochemical sensor was used in the determination of GLY in river and drinking water samples. Cyclic voltammetry and amperometry were used as electrochemical detection techniques for the characterization and analytical application of the developed biosensor. The working mechanism of the biosensor is based on the inhibition of the peroxidase enzyme by GLY. Under optimal experimental conditions, the biosensor showed a linear response in the concentration range of 0.1 to 10 mg L-1. The limits of detection and quantification are 0.025 ± 0.002 and 0.084 ± 0.007 mg L-1, respectively, which covers the maximum residual limit established by the EPA for drinking water (0.7 mg L-1). The proposed biosensor demonstrated high reproducibility, excellent analytical performance, repeatability, and accuracy. The sensor proved to be selective against other pesticides, organic acids, and inorganic salts. Application on real samples showed recovery rates ranging between 98.18 ± 0.11 % and 97.32 ± 0.23 %. The analytical features of the proposed biosensor make it an effective and useful tool for the detection of GLY for environmental analysis.

Removal of Contaminants from Water by Membrane Filtration: A Review.

Drinking water sources are increasingly subject to various types of contamination due to anthropogenic factors and require proper treatment to remove disease-causing agents. Public drinking water systems use different treatment methods to provide safe and quality drinking water to populations. However, they are ineffective in removing contaminants that are considered a danger to the environment and therefore to humans. Several alternative treatment processes have been proposed, such as membrane filtration, as final purification methods. This paper aims to summarize the type of pollutant compounds, filtration processes, and membranes that have been most studied in this area with particular emphasis on how the modification of membranes, either the manufacturing process or the incorporation of nanomaterials, influences their performance.

Addressing the Detection of Ammonium Ion in Environmental Water Samples via Tandem Potentiometry-Ion Chromatography.

An analytical methodology for detecting ammonium ion (NH4 +) in environmental water through potentiometry-ion chromatography (IC) in tandem is presented here. A multielectrode flow cell is implemented as a potentiometric detector after chromatographic separation of cations in the sample. The electrodes are fabricated via miniaturized all-solid-state configuration, using a nonactin-based plasticized polymeric membrane as the sensing element. The overall analytical setup is based on an injection valve, column, traditional conductometric detector, and new potentiometric detector (in that order), permitting the characterization of the analytical performance of the potentiometric detector while validating the results. The limit of detection was found to be ca. 3 × 10-7 M NH4 + concentration after linearization of the potentiometric response, and intra- and interelectrode variations of <10% were observed. Importantly, interference from other cations was suppressed in the tandem potentiometry-IC, and thus, the NH4 + content in fresh- and seawater samples from different locations was successfully analyzed. This analytical technology demonstrated a great potential for the reliable monitoring of NH4 + at micromolar levels, in contrast to the conductivity detector and previously reported NH4 + potentiometric sensors functioning in batch mode or even coupled with IC. Additionally, the suitability of the potentiometric cell for selective multi-ion analysis in the same sample, i.e., Na+, NH4 +, and K+ in water, has been proven.

HPLC-potentiometric method for determination of biogenic amines in alcoholic beverages: A reliable approach for food quality control.

Determination of ten biogenic amines in alcoholic beverages by HPLC coupled to a potentiometric detector for food quality control is herein presented. Biogenic amines were separated by ion-pair chromatography on a C18 column using a gradient mobile phase of acetic acid, acetonitrile, and butane-sulfonic acid. Detection was accomplished by a miniaturized amine-selective electrode. The method was validated following ICH and Eurachem guidelines. Linear regression models provided R2 values from 0.9870 ± 0.0019 to 0.9991 ± 0.0014 for tyramine and cadaverine, respectively. Detection and quantification limits depend on the molecular weight of BAs, ranging from 9.3 to 60.5 and from 31.1 to 202.3 µg L-1 for methylamine and spermine, respectively. Repeatability and intermediate precision showed RSD values lower than 5.8 and 8.3%, respectively. Accuracy of assays yielded recovery values from 86.4 to 109.9%. The biogenic amines content in red wine, white wine, and beer samples were 7.54, 5.24, and 4.58 mg L-1, respectively.

Supramolecular Atropine Potentiometric Sensor.

A supramolecular atropine sensor was developed, using cucurbit[6]uril as the recognition element. The solid-contact electrode is based on a polymeric membrane incorporating cucurbit[6]uril (CB[6]) as an ionophore, 2-nitrophenyl octyl ether as a solvent mediator, and potassium tetrakis (4-chlorophenyl) borate as an additive. In a MES-NaOH buffer at pH 6, the performance of the atropine sensor is characterized by a slope of (58.7 ± 0.6) mV/dec with a practical detection limit of (6.30 ± 1.62) × 10-7 mol/L and a lower limit of the linear range of (1.52 ± 0.64) × 10-6 mol/L. Selectivity coefficients were determined for different ions and excipients. The obtained results were bolstered by the docking and spectroscopic studies which demonstrated the interaction between atropine and CB[6]. The accuracy of the potentiometric analysis of atropine content in certified reference material was evaluated by the t-Student test. The herein proposed sensor answers the need for reliable methods providing better management of this hospital drug shelf-life while reducing its flush and remediation costs.

Challenges in the design of electrochemical sensor for glyphosate-based on new materials and biological recognition.

Glyphosate (GLY) is the main ingredient in the weed killer Roundup and the most widely used pesticide in the world. Studies of the harmful effects of GLY on human health began to become more wide-ranging after 2015. GLY is listed by the International Agency for Research on Cancer (IARC) as a carcinogenic hazard to humans. Moreover, GLY has the property to complex with transition metals and are stable for long periods, being considered a high-risk element for different matrices, such as environmental (soil and water) and food (usually genetically modified crops). Since that, it was noticed an increment in the development of new analytical methods for its determination in different matrices like food, environmental and biological fluids. Noteworthy, the application of electrochemical techniques for downstream detection sparked interest due to the ability to minimize or eliminate the use of polluting chemicals, using simple and affordable equipment. This work aims to review the contribution of the electroanalytical methods for the determination of GLY in different food and environmental matrices. Parameters such as the electrochemical transduction techniques based on the electrical measurement signals, receptor materials for electrodes preparation, and the detection mechanisms are described in this review. The literature review shows that the electrochemical sensors are powerful detection system that can be improved by their design and by their portability to fulfil the needs of the GLY determination in laboratory benches, or even in situ analysis.

Author Correction: Challenges in the serological evaluation of dogs clinically suspect for canine leishmaniasis.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Challenges in the serological evaluation of dogs clinically suspect for canine leishmaniasis.

Canine leishmaniasis is a major veterinary issue and also a public health challenge due to its zoonotic potential. In this context, serological evaluation is essential for Canine leishmaniasis management. Several serological alternatives, such as rapid diagnostic tests, enzyme-linked immunosorbent assay (ELISA) and immunofluorescence antibody test (IFAT), are well established. In fact, the capacity of distinct tests and antigens, evaluated by their sensitivity and specificity, to detect disease is normally considered sufficient for diagnosing Canine leishmaniasis. In this context, we evaluated the seropositivity using 8 different serological tests (ELISA with Leishmania recombinant proteins (rK39, LicTXNPx); soluble promastigote Leishmania antigens (SPLA); commercial ELISA test) in 82 clinically suspect animals from Northern Portugal. The obtained serological data originated 50% of inconclusive serological information with a mixture of seropositive and seronegative results for individual animals. Cut-off independent risk groups were then generated from the serological data to evaluate the clustering of the samples. This analysis originated risk groups that correlated with the most seropositive samples, suggesting that this method might be used, in a cut-off independent manner, to improve conventional serological evaluation. Ultimately, given that no test prioritization exists, the use of any single serological test increases the potential for misdiagnosis, along with all associated risks for the dog as well as public health. The use of a cut-off independent analysis has the potential to improve the predictive values of these tests, enabling a more accurate evaluation of the dog's condition.

Biosensing based on pencil graphite electrodes.

Pencil leads have been increasingly used as electrode material in electrochemical applications. Commonly denominated as pencil graphite electrodes (PGE), they represent a viable alternative to other standard electrodes due to their comparable electrical properties but mainly for their low cost and availability, enabling disposable applications. In order to achieve the best analytical performance literature evidences the type of lead (hardness level) and electrode surface pre-treatment are critical to the envisaged application. The present review describes the use of PGE in biosensing analysis, more specifically those sensors comprising immobilized enzymes but also briefly referring nucleic acids and other biological entities. It lays an emphasis in the immobilization process of the biological entities while focusing in the analytical performance of each biosensor, mainly sensitivity, linear range and limit of detection as comparative criteria. This review also addresses the main characteristics and properties of PGEs as transducer material in the electrochemical field.

Potentiometric perchlorate determination at nanomolar concentrations in vegetables.

In this work, an expeditious method based on the multi-commutated flow-analysis concept with potentiometric detection is proposed to perform determinations of the emergent contaminant perchlorate in vegetable matrices down to nanomolar concentration. To accomplish the task, a tubular shaped potentiometric sensor selective to perchlorate ion was constructed with a PVC membrane containing 12mmol/kg of the polyamine bisnaphthalimidopropyl-4,4'-diaminodiphenylmethane and 2-nitrophenyl phenyl ether 68% (w/w) as plasticizer casted on a conductive epoxy resin. Under optimal flow conditions, the sensor responded linearly in the concentration range of 6.3×10-7-1.0×10-3mol/L perchlorate. In order to extend the determinations to lower concentrations (4.6(±1.3)×10-10mol/L perchlorate), a column packed with 70mg of sodium 2,5,8,11,14-pentaoxa-1-silacyclotetradecane-polymer was coupled to the flow-system thus enabling prior pre-concentration of the perchlorate. The proposed procedure provides a simpler alternative for the determination of perchlorate in foods, nowadays only allowed by sophisticated and expensive equipment and laborious methods.

Vortex-assisted liquid-liquid micro-extraction and high-performance liquid chromatography for a higher sensitivity methyl methacrylate determination in biological matrices.

A vortex-assisted liquid-liquid micro-extraction coupled with high-performance liquid chromatography, with UV-vis, is proposed to pre-concentrate methyl methacrylate and to improve separation in biological matrices. The use of 1-octanol as extracting phase, its volume, the need for a dispersant agent, the agitation conditions and the cooling time before phase separation were evaluated. In optimum conditions, enrichment factors of 20 (±0.5) and enrichment recovery of 99% were obtained. The straightforward association of this extraction process with the HPLC method, previously regulated by the International Organization for Standardization, afforded a detection limit of 122 ng/mL and a quantification limit of 370 ng/mL. The within-batch precision, relative standard deviation, was 3% for a sample with 1.49 µg/mL and 4% for a sample with 13.4 µg/mL. The results showed a between batch-precision of 21% for experiments performed on five different days, for a sample with a concentration of 1.10 µg/mL in methyl methacrylate.

Fully automated analytical procedure for propofol determination by sequential injection technique with spectrophotometric and fluorimetric detections.

In this work, an application of an enzymatic reaction for the determination of the highly hydrophobic drug propofol in emulsion dosage form is presented. Emulsions represent a complex and therefore challenging matrix for analysis. Ethanol was used for breakage of a lipid emulsion, which enabled optical detection. A fully automated method based on Sequential Injection Analysis was developed, allowing propofol determination without the requirement of tedious sample pre-treatment. The method was based on spectrophotometric detection after the enzymatic oxidation catalysed by horseradish peroxidase and subsequent coupling with 4-aminoantipyrine leading to a coloured product with an absorbance maximum at 485 nm. This procedure was compared with a simple fluorimetric method, which was based on the direct selective fluorescence emission of propofol in ethanol at 347 nm. Both methods provide comparable validation parameters with linear working ranges of 0.005-0.100 mg mL(-1) and 0.004-0.243 mg mL(-1) for the spectrophotometric and fluorimetric methods, respectively. The detection and quantitation limits achieved with the spectrophotometric method were 0.0016 and 0.0053 mg mL(-1), respectively. The fluorimetric method provided the detection limit of 0.0013 mg mL(-1) and limit of quantitation of 0.0043 mg mL(-1). The RSD did not exceed 5% and 2% (n=10), correspondingly. A sample throughput of approx. 14 h(-1) for the spectrophotometric and 68 h(-1) for the fluorimetric detection was achieved. Both methods proved to be suitable for the determination of propofol in pharmaceutical formulation with average recovery values of 98.1 and 98.5%.

A SO2-selective electrode based on a Zn-porphyrin for wine analysis.

This work describes the assessment of a SO2-selective electrode based on the use of the neutral carrier 5,10,15,20-tetraphenyl(porphyrinate)zinc(II) in a PVC membrane plasticized with 2-nitrophenyl phenyl ether. After being conditioned in 2 mol L(-1) diethylamine solution for 24 h, the electrode exhibited selective anionic response toward the analyte in a concentration interval of more than four decades, with an slope of -59.5 mV dec(-1), a practical detection limit of 3.7×10(-6) mol L(-1) and a low limit of linear range of 7.2×10(-6) mol L(-1). The response mechanism is based on the displacement of the diethylamine:metalloporphyrin complex equilibrium within membrane bulk, inducing a variation in the cationic-sites to ionophore ratio. In turn, free hydroxyl ions are complexed by the displaced ionophore in a ratio 1:1 and translated as single negative charge nernstian response. Finally, the selectivity of the electrode is evaluated in view of its application to wine analysis. Results had high accuracy and precision when compared with a reference method.

Pilot monitoring study of ibuprofen in surface waters of north of Portugal.

Ibuprofen is amongst the most worldwide consumed pharmaceuticals. The present work presents the first data in the occurrence of ibuprofen in Portuguese surface waters, focusing in the north area of the country, which is one of the most densely populated areas of Portugal. Analysis of ibuprofen is based on pre-concentration of the analyte with solid phase extraction and subsequent determination with liquid chromatography coupled to fluorescence detection. A total of 42 water samples, including surface waters, landfill leachates, Wastewater Treatment Plant (WWTP), and hospital effluents, were analyzed in order to evaluate the occurrence of ibuprofen in the north of Portugal. In general, the highest concentrations were found in the river mouths and in the estuarine zone. The maximum concentrations found were 48,720 ng L(-1) in the landfill leachate, 3,868 ng L(-1) in hospital effluent, 616 ng L(-1) in WWTP effluent, and 723 ng L(-1) in surface waters (Lima river). Environmental risk assessment was evaluated and at the measured concentrations only landfill leachates reveal potential ecotoxicological risk for aquatic organisms. Owing to a high consumption rate of ibuprofen among Portuguese population, as prescribed and non-prescribed medicine, the importance of hospitals, WWTPs, and landfills as sources of entrance of pharmaceuticals in the environment was pointed out. Landfill leachates showed the highest contribution for ibuprofen mass loading into surface waters. On the basis of our findings, more studies are needed as an attempt to assess more vulnerable areas.