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Asphaltene destabilization is still known as one of the main problems of the petroleum industry and imposes many costs on this industry during crude oil production, transportation, and refining. The most important solution to control this problem is using chemical compounds to disperse asphaltene aggregates. Ionic liquids, as an emerging industrial solvent and catalyst, have been used for this purpose in the last two decades. In this work, three ionic liquids having a tetrabutylammonium cation and oleate, stearate, and cinnamate anions were synthesized and used as asphaltene dispersants. The efficiency of the synthesized ionic liquids on the stability of asphaltene aggregates was investigated using cluster size, polydispersity index, zeta potential, and ultraviolet spectroscopy data. It was found that tetrabutylammonium cinnamate and tetrabutylammonium oleate (dispersion indices of 82.5 and 60.2, respectively) have a much higher efficiency than tetrabutylammonium stearate (dispersion index of 20.6). The results of cluster size, polydispersity index, and zeta potential analysis were confirmed by ultraviolet spectroscopy and optical microscopy data. For instance, the mean radius of asphaltene clusters was 2179.8 nm, reduced to 253, 680, and 1402 nm after adding tetrabutylammonium salt of cinnamate, oleate, and stearate, respectively. The same trend was observed in the results of the polydispersity index (0.417, 0.470, and 0.624) and zeta potential analysis (31.4, 1.81, and −0.56). The cinnamate, oleate, and stearate anions have four, one, and no carbon–carbon π bonds, respectively. It seems that the presence of π bonds that can form π–π interactions with π bonds of the asphaltene molecules is an essential factor in asphaltene stabilization by these ionic liquids. In addition, the results showed that the higher the net negative charge of the anion, the greater the ability of the anion to stabilize asphaltene aggregates. This stabilization, which was mainly done through electrostatic interactions between polar groups of asphaltene and the carboxylate anions, was confirmed by zeta potential data.

•Application of ten Tetraalkylammonium and phosphonium salt were evaluated as asphaltenes and dispersant.•The systematic study using UV–vis spectroscopy was done to investigate interactions between asphaltenes and organic salts based on the size and the shape of the cations and anions.•The length of alkyl chain in cations and hydrophobicity of anion have crucial role in preventing of asphaltene stacking interactions.•This mechanistic study was revealed that the role of anions on the stability of asphaltene aggregates is more important than cations.

A novel method is presented here for trace determination of celecoxib by fluorescence detection using curcumin nanoparticles (CurNPs) loaded on multi-walled carbon nanotubes with carboxyl functional groups (CurNPs–MWCNT–COOH). For the synthesis of CurNPs–MWCNT–COOH, CurNPs were retained on carbon nanotubes with the aid of ultrasound waves. The sensing method is based on monitoring the quenching of synthesized CurNPs–MWCNT–COOH fluorescence by celecoxib. The morphology of CurNPs–MWCNT–COOH was studied by transmission electron microscopy (TEM) of the composite alone and in the presence of celecoxib. The effects of several parameters on the production of CurNPs–MWCNT–COOH and determination of celecoxib such as the Triton X-100 concentration, the amount of MWCNT–COOH and the pH were evaluated and optimum conditions were established. The calibration graph was found to be linear in the range of 20–220 ng mL−1for celecoxib in the initial solution. The detection limit based on three times the standard deviation of the blank was 5.8 ng mL−1for celecoxib and relative standard deviations (RSD) of 3.6% and 1.8% were obtained for eight replicate determinations of 60 ng mL−1and 180 ng mL−1of celecoxib, respectively. The method was applied to the determination of celecoxib in serum samples.

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Phthalate esters are synthetic chemicals that are widely used in plastic industries as plasticizer. They are harmful to humans and could be carcinogenic. In this research, a new nanosorbent was prepared viaa Schiff-base reaction between p-dimethylaminobenzaldehyde and Fe3O4@SiO2-NH2nanoparticles. A characterization of the sorbent was performed by Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and energydispersive spectroscopy. A modified nanosorbent has a core shell structure, and shows a great tendency towards the sorption of phthalate esters. Hence, it was utilized for the dispersive solid-phase extraction of six phthalate esters and determination by gas chromatography-flame ionization detection. Several variables, such as the pH, sorbent amount, salt effects, extraction and desorption time, extraction solvent type and volume, were investigated to establish the optimal conditions. Calibration graphs were linear in the range of 1.0–150.0 μg L−1for dimethyl phthalate, bis-(2-ethylhexyl) phthalate, di-n-octyl phthalate and 0.1–200.0 μg L−1for diethyl phthalate, di-n-butyl phthalate and butyl benzyl phthalate, respectively. The obtained limits of detections (S/N= 3) were in the range of 0.02–0.31 μg L−1. Application of the method for the enrichment and determination of phthalate esters in mineral water, natural low fat yogurt and sodium chloride infusion (0.9%, w/v) was investigated.

This article presents a sensitive and straightforward colorimetric chemosensor for the determination of phosphate ion utilizing curcumin nanoparticles (CUNPs) as the sensing system. The color of as-prepared CUNPs can be changed from yellow to orange upon adding iron(III) ions due to the formation of a complex with CUNPs. However, in the presence of phosphate ions, iron(III) ions prefer to bind to phosphate ions and, subsequently the color of CUNPs is selectively recovered because of releasing the iron(III) ions from the CUNPs-iron(III) complex. Therefore, in this work the selective color changing of the CUNPs-iron(III) system upon the addition of phosphate ions was used for the quantitative sensing of phosphate ions. Various factors, such as the pH, concentration of iron(III) and volume of CUNPs, were examined and the optimum conditions were established. A linear calibration graph over the range of 10–400 ng mL–1for phosphate (r= 0.9995) was achieved using the optimal conditions. The limit of detection (LOD) of the proposed method for phosphate was 7.1 ng mL–1and the relative standard deviation (RSD) for measuring 50 ng mL–1of phosphate was 3.7% (n= 8). The developed method was applied for the measurement of phosphate in water, soil, and bone samples. Satisfactory results were obtained.

The presence of antibiotics in the environment threatens the health of humans and animals, seriously. In this respect, this study applies cerium oxide nanoparticles (CeO2NPs) as an adsorbent to remove tetracycline (TC) from aqueous solutions and investigates the effects of various parameters on the adsorption reaction. The studied parameters include pH‚ electrolyte concentration‚ TC concentration, amount of the adsorbent, flow rate of the solution, and the presence of several coexisting ions. According to the obtained results, the CeO2NPs are quite efficient for removal of TC at room temperature. Furthermore, adsorption of TC onto the CeO2NPs is fast and the corresponding isotherms fit the Langmuir model, perfectly. The proposed adsorption method is successfully employed to remove TC from various aqueous solutions including surface and drinking water samples.

In this study, chitosan-SnO2nanoparticles biocomposite was synthesized and investigated as an efficient green biosorbent for adsorption of Fe(II) ions. The as-prepared bio-nanocomposite was characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction spectroscopy, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Furthermore, a dispersive micro-solid phase extraction (D-μ-SPE) based on microvolume spectrophotometric detection technique was developed for preconcentration as well as determination of Fe(II) ions in environmental and wastewater samples. After reduction of Fe(III) ions by the addition of hydroxylamine hydrochloride as reducing agent, the system was applied to the total iron. Different parameters influencing the extraction efficiency including sample pH, the amount of adsorbent, adsorption time, and properties of desorption solvent were optimized. The adsorption isotherms of the synthesized adsorbent were also studied. The adsorption isotherm was well described by the Freundlich model and showed good adsorption capacity for the Fe(II) ions (17.24 mg g–1). The calibration graph was linear in the range 10–1,200 ng mL–1of Fe(II) and total iron. The detection limit of the method for determination of Fe(II) was 2.8 ng mL–1with a relative standard deviation of less than 1.3%. The adsorption capacity of the regenerated adsorbents was maintained at 90% even after the fourth adsorption–desorption cycle.

Herein, a novel fluorescence method has been developed for the determination of vitamin B12. The method is based on the interaction of vitamin B12 with silver nanoparticles embedded in chitosan (AgNPs–CH) followed by cloud point extraction using Triton X-100 as the nonionic surfactant followed by fluorescence detection. For fluorimetric detection, different excitation wavelengths were applied and an excitation wavelength of 250 nm and an emission wavelength of 337 nm were selected. The effect of different variables on the fluorescence intensity such as the pH of the sample solution, surfactant concentration, incubation temperature and time, electrolyte concentration and amount of AgNPs–CH was investigated. Under the approved conditions, a linear calibration curve was validated in the range of 0.2–15.0 ng mL−1of vitamin B12. The limit of detection (LOD) and the limit of quantification (LOQ) based on three and ten times the standard deviation of the blank were 0.036 and 0.119 ng mL−1, respectively. The relative standard deviation for eight replicate measurements of 1.0 and 7.0 ng mL−1of vitamin B12 was 2.92 and 2.45%, respectively. This probe was used for vitamin B12 determination in human plasma and urine samples with acceptable results and good recoveries.

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AbstractZirconia nanoparticles were modified by sodium dodecyl sulfate (SDS) under ultrasonic action and used as a new adsorbent for the removal of brilliant cresyl blue dye from aqueous solutions. The effect of different parameters such as pH, salt concentration, and amount of adsorbent on the removal procedure was studied and optimum conditions were established. The adsorption data were fitted to Langmuir, Freundlich, and Temkin isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model. The kinetic studies indicated that the experimental data were fitted well by the pseudo-second-order model. The maximum adsorption capacity was found to be 34.4 mg g−1of adsorbent for brilliant cresyl blue. The removal procedure was applied to the removal of brilliant cresyl blue form water samples.

Zirconia nanoparticles were modified by sodium dodecyl sulfate (SDS) under ultrasonic action and used as a new adsorbent for the removal of brilliant cresyl blue dye from aqueous solutions. The effect of different parameters such as pH, salt concentration, and amount of adsorbent on the removal procedure was studied and optimum conditions were established. The adsorption data were fitted to Langmuir, Freundlich, and Temkin isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model. The kinetic studies indicated that the experimental data were fitted well by the pseudo-second-order model. The maximum adsorption capacity was found to be 34.4 mg g−1of adsorbent for brilliant cresyl blue. The removal procedure was applied to the removal of brilliant cresyl blue form water samples.

Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC. The platforms include a colorimetric-based sensor based on nanopaper containing embedded silver and gold nanoparticles; a photoluminescent-based sensor, comprising CdSe@ZnS quantum dots conjugated to nanopaper; and a potential up-conversion sensing platform constructed from nanopaper functionalized with NaYF4:Yb3+@Er3+&SiO2nanoparticles. We have explored modulation of the plasmonic or photoluminescent properties of these platforms using various model biologically relevant analytes. Moreover, we prove that BC is and advantageous preconcentration platform that facilitates the analysis of small volumes of optically active materials (∼4 μL). We are confident that these platforms will pave the way to optical (bio)sensors or theranostic devices that are simple, transparent, flexible, disposable, lightweight, miniaturized and perhaps wearable.

A new solid-phase extraction method for determination of palladium by atomic absorption spectrometry is described. Multiwalled carbon nanotube (MWCNT) modified with 1-butyl 3-methyl imidazolium hexafluorophosphate (MWCNT-[BMIM]PF6) and supported on sawdust was used as an adsorbent for preconcentration of palladium. Palladium ions are retained on (MWCNT-[BMIM]PF6) adsorbent as [PdI4]2−and eluted from the column with a thiosulfate–ammonia mixture. The optimum conditions for the adsorption were evaluated by changing various parameters such as pH, sample volume, concentration and volume of eluent, iodide concentration and interfering ions to achieve highest sensitivity and selectivity. The calibration graph was linear in the range of 2–120 ng mL−1of palladium in the initial solution and the limit of detection based on 3Sbwas 0.41 ng mL−1. The method was applied to the determination of palladium in water, wastewater and soil samples.

A new dispersive liquid–liquid microextraction (DLLME) method coupled with microvolume UV-vis spectrophotometry was developed for the determination of trace amounts of bismuth. The method is based on the complex formation of Bi(iii) with iodide (BiI4−) and extraction into carbon tetrachloride as an ion pair. The extraction is assisted by methyltrioctylammonium chloride, which also acts as a disperser agent. The effect of important parameters, such as the concentration of sulfuric acid and iodide in the sample solution, the amount of methyltrioctylammonium chloride, and the type and volume of extraction solvent were investigated and optimized. The present method is capable of determining bismuth in the concentration range of 5 to 400 ng mL−1with a limit of detection (LOD) of 1.6 ng mL−1. The relative standard deviation for eight replicate measurements of Bi(iii) at concentrations of 200 and 75 ng mL−1was calculated to be 1.14 and 2.66%, respectively. The developed method was successfully applied to the determination of bismuth in bismuth subcitrate tablets and human serum samples.

Silver nanoparticles exhibit the optical properties of surface plasmon resonance (SPR). This paper describes a method based on both SPR and cloud point extraction of silver nanoparticles (AgNPs) for the determination of copper. Label free AgNPs are enriched into a non-ionic surfactant phase and show strong SPR intensity. Copper(ii) suppresses the transfer of AgNPs into the surfactant and decreases the SPR intensity. The decrease in the absorbance of the surfactant rich phase in the presence of Cu(ii) is used as an analytical signal for the determination of copper. The influence of chemical variables such as pH of the sample solution, ionic strength, and concentration of the AgNPs on the cloud point extraction was investigated. Under the optimum conditions, the extent of the decrease in SPR absorption intensity was linearly proportional to the concentration of Cu(ii) in the range of 0.5–60.0 μg L−1with a detection limit of 0.1 μg L−1. The relative standard deviation of ten replicate measurements of 40 μg L−1of Cu(ii) was 3.7%. The proposed method was successfully applied in the determination of Cu(ii) in food samples with satisfactory results.

ABSTRACTA simple and sensitive kinetic method for the determination of vanadium(V) based on its inhibitory effect on the reduction of thionine by ascorbic acid at pH=5 is described. The reaction rate is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 598 nm after a fixed time (10 min). The calibration graph is linear in the range of 10 − 120 ng ml−1of vanadium(V) and the detection limit is 6 ng ml−1. The relative standard deviation (RSD) for 80 ng ml−1of V(V) was 0.96% (n=10). The method was successfully applied to the determination of vanadium in a certified reference sample.