New fabrication of CuFe2O4/PAMAM nanocomposites by an efficient removal performance for organic dyes: Kinetic study.

Today, removing pollutants from water sources is essential because of the population increase and the growing need for safe drinking water. Dyes are one of the most critical pollutants from industrial effluents such as paper and textile industries that profoundly affect the environment. There are several ways to remove environmental contaminants. Magnetic nanoparticles have a high ability to adsorb dyes. Of course, increasing the interaction between magnetic nanomaterials and pollutants is also essential, which can be done using porous materials such as dendrimers. In this work, the synthesis of CuFe2O4 magnetite nanoparticles within the polyamidoamine dendrimers structure was used as an efficient sorbent to remove both alizarin reds (ARS) and brilliant green (BG) dyes. Moreover, various parameters for dyes removal were studied. The optimum removal conditions were obtained for ARS within 30 min at a sorbent dose of 2 mg per 5 mL for the initial dye concentration of 7.0 ppm in pH 6 at 25 °C, and for BG within 45 min at a sorbent dose of 5 mg per 5 mL for the initial dye concentration of 17.0 ppm in pH 8 at 25 °C. At the optimum values of the above parameters, both dyes' removal efficiency was more than 97%. Also, the obtained results showed that the adsorption isotherm follows the Langmuir model and Temkin model for ARS and BG, respectively. This method was successfully used for the removal of both dyes in water samples.

Fluorescence detection of laccases activity by the photoinduced electron transfer (PET) process.

Laccases play a vital role in some physiological processes, for example in morphogenesis, carbon cycle, and defense against parasitism. So, designing a high-sensitivity accurate method is essential for researchers. In this study, a simple fluorescence method based on the function of carbon nitride (g-C3N4) by dopamine is synthesized. For the design of this sensor, carbon nitride (g-C3N4) is initially synthesis by using a simple method, which is carried out by heating melamine at 550 °C for 3 h and modifying it with dopamine by a linker such as glutaraldehyde. However, the g-C3N4-Dopa produced by this method, with an excitation wavelength of 330 nm, has a fluorescence emission at 466 nm. When laccase and g-C3N4-Dopa were mixed, dopamine with redox property was oxidized to dopaquinone; this causes the phenomenon of photoinduced electron transfer (PET) process between g-C3N4 and the dopaquinone. Hence, fluorescence quenching occurs due to this phenomenon. As a result of these discussions, a sensor for the laccase activity was designed based on the fluorescence quenching degree, supporting a linear range of 0.0-400.0 U L-1 with the detection limit of 2.0 U L-1. Using this sensor, the activity of the laccase enzyme in the human serum samples is measured. Dopamine-functionalized carbon nitride was prepared and utilized for the highly sensitive detection of laccases activity.

A hierarchical 3D camellia-like molybdenum tungsten disulfide architectures for the determination of morphine and tramadol.

A practical technique was applied to fabricate MoWS2 nanocomposite through a one-pot hydrothermal method for use as the electrocatalyst. The characterization of MoWS2 nanocomposite was investigated by several techniques to identify the size, crystal structure, and elemental composition. MoWS2 nanocomposite exhibited a unique and well-defined hierarchical structure with neatly and densely piled nanopetals acting as the active sites in the electrocatalytic reactions. A carbon screen-printed electrode (CSPE) modified with interesting MoWS2 nanopetals (MoWS2/CSPE) was constructed. Subsequently, the electrochemical oxidation of morphine on fabricated MoWS2/CSPE was studied. Experimental results confirm that under optimized conditions, the maximum oxidation current of morphine occurs at 275 mV in the case of MoWS2/CSPE that is around 100 mV more negative than that observed in the case of the unmodified CSPE and about 2.6 times increase was observed for the oxidation peak current. The analytical approach was obtained by differential pulse voltammetry in accordance with the relationship between the oxidation peak current and the morphine concentration. The oxidation peak currents for morphine were found to vary linearly with its concentrations in the range of 4.8 × 10-8-5.05 × 10-4 M with the detection limit of 1.44 × 10-8 M. Two completely separated signals occured at the potentials of 275 mV and 920 mV for oxidation of morphine and tramadol at the surface of MoWS2/CSPE which are sufficient for determination of morphine in the presence of tramadol. The presence of morphine was also detected in real samples using the introduced approach. Graphical abstract Schematic representation of fabrication of the MoWS2 nanocomposite through a one-pot hydrothermal method for use as the electrocatalyst. A carbon screen-printed electrode was modified with MoWS2 nanocomposite. Subsequently, the electrochemical oxidation of morphine on the fabricated electrode was studied.

Simultaneous voltammetric determination of glutathione, doxorubicin and tyrosine based on the electrocatalytic effect of a nickel(II) complex and of Pt:Co nanoparticles as a conductive mediator.

Glutathione (GSH) is an important tripeptide that plays an important role in preventing damage to reactive oxygen species. An electrochemical assay was fabricated for this purpose by modification of a carbon paste electrode (CPE) with bis(1,10-phenanthroline)(1,10-phenanthroline-5,6-dione)nickel(II) hexafluorophosphate (BPPDNi) as new electro-catalyst and Pt:Co nanoparticle (Pt:CO-NPs) as highly conductive mediator. The analyses were performed at a scan rate of 10 mV/s and at a pH value of 7.4. The BPPDNi/Pt:CO-NPs/CPE showed a high sensitivity and good selectivity for electro-catalytic determination of glutathione (GSH) in nano-molar concentration range. In addition, the BPPDNi/Pt:CO-NPs/CPE was used for the determination of glutathione in the presence of doxorubicin (DOX) and tyrosine (Tyr) with three separated oxidation signals ~160 mV, ~385 mV and ~790 mV vs. Ag/AgCl/KClsat, respectively. The peak currents of the square wave voltammetric analyses were linearly dependent on glutathione, doxorubicin and tyrosine concentrations in the respective ranges of 0.001-450, 0.5-300 and 1.0-650 µM, with detection limits of 0.5 nM, 0.1 µM and 0.6 µM, respectively. Graphical abstract The first analytical sensor for simultaneous determination of glutathione, doxorubicin and tyrosine.

Application of dispersive liquid-liquid-solidified floating organic drop microextraction and ETAAS for the preconcentration and determination of indium.

A new, simple and efficient method, including dispersive liquid-liquid-solidified floating organic drop microextraction and then electrothermal atomic absorption spectrometry, has been developed for the preconcentration and determination of ultratrace amounts of indium. The method was applied to preconcentrate the indium-1-(2-pyridylazo)-2-naphthol complex in 25 µL 1-undecanol. The various factors affecting the extraction efficiency, such as pH, type and volume of extraction solvent, type and volume of disperser solvent, sample volume, ionic strength, and ligand concentration, were investigated and optimized. Under the optimum conditions, an enrichment factor of 62.5, precision of ±4.75%, a detection limit of 55.6 ng L-1, and for the calibration graph a linear range of 96.0-3360 ng L-1 were obtained. The method was used for the extraction and determination of indium in water and standard samples with satisfactory results. Graphical Abstract Preconcentration of indium ions via liquid-liquid-solidified floating organic drop microextraction method and determination by ETAAS.

Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples.

In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values.

Determination of ultra trace amounts of copper by a multi-injection technique of electrothermal atomic absorption spectrometry after using solid-phase extraction.

A new method using a multi-injection technique combined with SPE was developed for the determination of copper (Cu) in environmental samples. The method is based on SPE of copper ions on naphthalene as its 2-(5-bromo-2-pyridylazo)- 5-diethylaminophenol (5-Br-PADAP)-ammonium tetraphenylborate complex, in the pH range 6.0-9.5, and determined by electrothermal atomic absorption spectrometry. No chemical modifier is required in the graphite furnace. The detection limit can be reduced to 1.5 ng/L using an injection volume of 25.0 µL (five 5.0 µL) without interference by the matrixes. The optimum pyrolysis and atomization temperatures were 500 and 2200°C, respectively, for the concentrated solution of Cu. The sensitivity for 1% absorption was 2.6 pg Cu. Eight replicate determinations for 0.1 µg Cu in 5.0mL dimethylformamide gave an RSD of 2.3% for a single injection and 2.7% for a multi-injection. The procedure was validated with certified reference materials and successfully applied to the determination of copper in water and plant samples.

Separation and preconcentration of trace amounts of rhodium using a dispersive liquid-liquid microextraction method and its determination by flame atomic absorption spectrometry.

A sensitive and selective method for the determination of low levels of rhodium (Rh) in environmental samples is needed. In the proposed method, an extracting solvent with a lower toxicity and density than the other solvents typically used in dispersive liquid-liquid microextraction was used to extract trace amounts of Rh from aqueous samples. Rh ions were complexed with 1-(2-pyridylazo)-2-naphthol in the pH range of 3.2-4.7 and extracted with dispersive liquid-liquid microextraction. The type and volume of the extracting solvent and dispersive solvent, centrifugation time, pH, amount of the chelating agent, and sample ionic strength were carefully studied. Under the optimal conditions, the LOD and RSD were 0.36 ng/mL (3Sb/m, n = 7) and +/-2.0% (n = 7), respectively. The calibration curve was linear in the range of 4.0-800 ng/mL. The method was applied to the determination of Rh in well and tap water, and spiked recoveries were in the range of 96-103.7%.

Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

Application of nanoclay for preconcentration of ultra trace amounts of palladium in environmental samples prior to its determination by ETAAS.

In the present work, a batch preconcentration technique using nanoclay with 5-(4-dimethylaminobenzylidene)rhodanine coupled with electrothermal atomic absorption spectrometry was developed for the separation and determination of trace amounts of palladium. In this method, the sample solution was stirred with nanoclay as an adsorbent. Then, adsorbed palladium was subsequently eluted with HCl in acetone (1.5 mol L−1) and, finally, this eluate was injected to electrothermal atomic absorption spectrometry. Under the optimum conditions, the limit of detection and linear dynamic range were found to be 2.6 and 10.0­133 ng L−1 (in original solution), respectively. Furthermore, the enrichment factor and relative standard deviation of seven replicate determinations were 148 and ±5.1 %, respectively. This suggested method is simple, selective and sensitive and can be applied to the extraction and determination of palladium in water, tea leaves, synthetic sample and certified reference material with satisfactory results.

Potentiometric determination of trace amounts of aluminium utilizing polyvinyl chloride membrane and coated platinum sensors based on E-N'-(2-hydroxy-3-methoxybenzylidene) benzohydrazide.

This paper describes the construction and performance characteristics of novel polyvinyl chloride membrane (PME) and coated platinum (CPtE) aluminium (Al) ion selective electrodes based on E-N'-(2-hydroxy-3-methoxybenzylidene) benzohydrazide. The electrodes exhibited linear responses with near Nernstian slopes of 19.9 +/- 0.3 (PME) and 20.1 +/- 0.4 (CPtE) mV/decade of activity within the Al3+ ion concentration range of 3.0 x 10(-7) to 1.0 x 10(-2) M for the PME and 1.0 x 10(-7)-1.0 x 10(-2) M for the CPtE. These sensors were applicable in a pH range of 3.0 to 7.0. The LODs of the PME and CPtE were 1.7 x 10(-7) and 5.6 x 10(-8) M, respectively. They had a response time of less than 10 s and could be used practically for a period of at least 2 months without measurable divergence in results. The isothermal temperature coefficient of the PME was 1.12 x 10(-3) V/degrees C, and it can tolerate partially nonaqueous media up to 25%. The electrodes showed excellent selectivity towards Al3+ ions in the presence of a wide range of alkali, alkaline earth, and transition metals ions. They were successfully applied for the direct determination of Al3+ ions in tap water, aqueduct water, mineral water, and Al-Mg syrup and as indicator electrodes in potentiometric titration of Al ions with EDTA.

Ligandless dispersive liquid--liquid microextraction of iron in biological and foodstuff samples and its determination by Electrothermal atomic absorption spectrometry.

A new, simple, and efficient method comprising ligandless dispersive liquid-liquid microextraction combined with electrothermal atomic absorption spectrometry is reported for the preconcentration and determination of ultratrace amounts of Fe(III). Carbon tetrachloride and acetone were used as the extraction and disperser solvents, respectively. Some effective parameters of the microextraction such as choice of extraction and disperser solvents, their volume, extraction time and temperature, salt and surfactant effect, and pH were optimized. Under the optimum conditions, the calibration curve was linear in the range of 0.02 to 0.46 microg/L of Fe(III), with LOD and LOQ of 5.2 and 17.4 ng/L, respectively. The RSD for seven replicated determinations of Fe(IIl) ion at 0.1 microg/L concentration level was 5.2%. Operational simplicity, rapidity, low cost, good repeatability, and low consumption of extraction solvent are the main advantages of the proposed method. The method was successfully applied to the determination of iron in biological, food, and certified reference samples.

Determination of ultra-trace amounts of cadmium by ET-AAS after column preconcentration with a new sorbent of modified MWCNTs.

The present research reports on the application of modified multiwalled carbon nanotubes as a new, easily prepared, and stable solid sorbent for the column preconcentration of ultra-trace amounts of cadmium in aqueous solution. Multiwalled carbon nanotubes were oxidized with concentrated HNO3 and modified with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and then were used as a solid phase for the column preconcentration of Cd(II). Elution was carried out with 0.5 mol L(-1) HNO3. The amount of eluted Cd(II) was measured using electrothermal atomic absorption spectrometry. Various parameters such as pH, sample and eluent flow rate, eluent concentration, breakthrough volume, and interference of a great number of anions and cations on the retention of analyte on sorbent were studied. Under the optimized conditions, the calibration graph was linear in the range of 0.67 ng L(-1) to 5.0 µg L(-1) and the detection limit (3Sb, n = 7) was 0.14 ng L(-1) in initial solution. A preconcentration factor of 300 and relative standard deviations of ± 3.6 % for seven successive determinations of 3 ng of Cd(II) were achieved. The column preconcentration was successfully applied to the analysis of river water, waste water, and Persian Gulf water sample.

Cu-BTC MOF/ionic liquid nanocomposite as novel catalyst to electrochemical monitoring of digoxin in pharmaceutical and environmental samples.

There is no effective environmental treatment strategy that does not include monitoring for pharmaceutical compounds in environmental and biological fluids. The widespread presence of pharmaceutical-based pollutants in water sources is a significant public health concern. The treatment process relies heavily on maintaining a stable digoxin concentration in bodily fluids. Finding the correct dose for this medication appears to be crucial. In this research, an easy and high sensibility electrochemical sensor was developed to determine digoxin based on a paste electrode (CPE) that was modified with Cu-BTC MOF and ion liquid ((IL); 1-Methyl-3-Butyl-imidazolinium bromide in this case) using voltammetric methods in 0.1 M phosphate buffer solution (PBS) at pH 5.0. The sensor's selectivity was significantly increased by using Cu-BTC MOF and IL to detect digoxin. The characteristics of the electrode modifiers were evaluated by SEM, XRD and EDS techniques. The LDR was found to be 0.1-40 µM and the LOD of 0.08 µM, respectively.

Developing an exclusive sensor based on molecularly imprinted polymer/Multi-walled carbon nanotubes/Fe3O4@Au nanocomposite for the selective determination of an anti-cancer drug imatinib.

Determination of pharmaceuticals especially anticancer drugs is one of the important issues in environmental and medical investigation and creating good information about human health. The presence sturdy introducing an electroanalytical sensor based on molecularly imprinted polymer (MIP)/Multi-walled carbon nanotubes (MWCNTs)/Au@Fe3O4 nanoparticles modified carbon paste electrode (PE) to determine imatinib (IMA). The MIP/MWCNTs/Au@Fe3O4/PE showed catalytic activity and also a sensitive strategy to sensing IMA in the concentration range 1-1000 µM with a limit of detection of 0.013 µM. The MIP/MWCNTs/Au@Fe3O4/PE has shown interesting results in the analysis of IMA in real samples, and the interference investigations results show the high selectivity of the MIP/MWCNTs/Au@Fe3O4/PE in the monitoring of IMA in complex fluids such as tablet and blood serum and results approved by F-test and t-test as statistical methods.

Fabrication of a new multi-walled carbon nanotube paste electrode for stripping voltammetric determination of Ag(I).

A new modified carbon paste electrode based on multi-walled carbon nanotubes and a synthesized Schiff base of N,N'-bis(2-hydroxybenzylidene)-2,2'(aminophenylthio) ethane, acting as a chelating agent for Ag(I) ions, is described. The electroanalytical procedure for the determination of Ag(I) was comprised of two steps: the chemical accumulation of the analyte under open-circuit conditions followed by replacing the medium with a 0.1 M HCl solution where the accumulated Ag(I) was reduced for 20 s in -0.7 V. The potential was then scanned from -0.2 to +0.2 V to obtain the voltammetric peak. The effective parameters in the sensor response were examined. Under optimized operational conditions, a linear response range from 0.5-200 ng mL(-1) was obtained. The detection limit for silver determination was 0.092 ng mL(-1). For 7 successive determinations of 15.0 and 60.0 ng mL(-1) of Ag(I), relative standard deviations of 2.2% and 1.2% were obtained, respectively. The procedure was applied in determining Ag(I) in X-ray photographic films and water samples.

Magnetic nanoparticles based on cerium MOF supported on the MWCNT as a fluorescence quenching sensor for determination of 6-mercaptopurine.

In this study, a new magnetic nanocomposite was developed as an efficient and fast-response fluorescence quenching sensor for determination of anticancer drug 6-mercaptopurine (6-MP). For this purpose, the needle-shape fluorescence metal-organic framework of cerium (Ce-MOF) were successfully synthesized on the surface of multiwalled carbon nanotubes using 1,3,5-benzenetricarboxylic acid ligand via a facile solvothermal assisted route and magnetized. The accuracy of the proposed synthesis was confirmed using the FT-IR, FE-SEM, XRD, and VSM methods. The obtained product as presented the fluorescence emission in 331 nm by excitation of 293 nm in excitation/emission slit widths of 10.0 nm. The operation of suggested method is based on quenching the fluorescence signal in accordance with increasing the 6-MP concentration. The proposed assay effectively detected the trace amount of 6-MP in the linear range of 1.0 × 10-6 to 7 × 10-5 M. The limit of detection and limit of quantification were obtained as 8.6 × 10-7 and 2.86 × 10-6 M, respectively. The analyte molecule was determined in real samples with satisfactory recoveries between 98.75 and 105.33.

Ultrasensitive and highly selective "turn-on" fluorescent sensor for the detection and measurement of melatonin in juice samples.

Melatonin (MLT), a hormone related to the regulation of brain functions, is directly related to sleep quality and is considered to be a possible adjuvant therapy for patients needing hospitalization for coronavirus disease 2019 pneumonia, and accurate measurement of MLT is crucial. Herein, a new, highly sensitive, and easy operation fluorescent probe was provided based on Zr metal-organic framework encapsulation into the molecularly imprinted polymer (MOF@MIP). By combining unique properties of MIP and fluorescent MOF, selectivity and operation of the applied method were significantly improved. Different characterization methods, such as XRD, FT-IR, and FE-SEM, were used to confirm the synthesis reliability. MOF@MIP was successfully used for the precise identification and ultrasensitive detection for trace amounts of MLT. The detection mechanism for the analytical system is based on the ''turn-on'' fluorescence (FL) signal in 404 nm. The findings proved that it is possible to detect trace amounts of MLT in real samples including grape, cherry, and sour cherry juice. The linear range and the limit of detection (LOD) for trace amounts of MLT were obtained as 1-100 ng/mL and 0.18 ng/mL, respectively.

Simple turn-off fluorescence sensor for determination of raloxifene using gold nanoparticles stabilized by chitosan hydrogel.

It is essential to develop a simple, applicable, and reliable assay to anticancer drug raloxifene (RAF) because of its significant usage and side effect due to entering residue in the environment. Fluorescence sensors developed and widely used because of them high selectivity, fast-response, and highly-sensitivity. The gold nanoparticles using chitosan hydrogel was synthesized and applied as a fluorescence sensor to determine the trace amount of RAF. The characterization methods including DLS, FE-SEM, EDX, XRD, and FT-IR were performed to confirm the synthesized structure. This sensor turned off the fluorescent signals proportional to RAF concentrations at 400 nm. The RAF can be detected in the linear range from 5 × 10-7 to 5 × 10-5 M. Limits of detection and quantification were obtained as 34 × 10-8 and 11 × 10-7 M as well as the relative standard deviation calculated as 1.63% in RAF measuring. The effective parameters on quenching efficiency were studied by central composite design (CCD) with response surface methodology (RSM). The effective parameters in RAF determination, include analyte concentration, temperature, contact time, and pH, were obtained as 35 µM, 30 °C, 8 min, and pH = 8.5. The sensor was applied to determine the RAF concentrations in biological and environmental samples with satisfactory recoveries between 97.5% and 109%.