Concentration Of PAN Research Articles

Natural deep eutectic based dispersive liquid-liquid microextraction and solidified floating organic drop for cadmium determination by electrothermal atomic absorption spectrometry with multivariate optimization (DLLME-SFOD-NADES-ETAAS)

A novel method was developed for cadmium determination based on dispersive liquid-liquid microextraction and solidified floating organic drop by multivariate optimization with electrothermal atomic absorption spectrometric detection using a natural deep eutectic solvent (NADES) of (L)-menthol and formic acid. Important factors, including pH, final concentration of PAN, mole ratio of formic acid, volume of NADES, type of dispersive solvent, and vortex time, were assessed using two-level fractional factorial design (FFD), and circumscribed central composite design (CCC). The analytical performance parameters, encompassing linearity range, limit of detection (LOD), limit of quantification (LOQ), and precision, were evaluated. The linearity range ranged from 0.72 to 2.50 ng/L, with corresponding LOD and LOQ values of 0.22 and 0.72 ng/L, respectively. Precision was evaluated by conducting three replicates of the three concentration levels, resulting in %RSD values of 11.8 %, 5.1 %, and 3.9 %, respectively. An enrichment factor (EF) of 112 was achieved. The optimized method was applied for cadmium determination in various matrices, including drinking water, environmental water, seafoods, yielding %recovery in the ranges of 78.05–102.41 %. Finally, comparison of t-values between the developed method and CRMs demonstrated satisfactory results at a 95 % confidence level.

Rapid and efficient determination of zinc in water samples by graphite furnace atomic absorption spectrometry after homogeneous liquid-liquid microextraction via flotation assistance

ABSTRACT. A new application of homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) has been developed for the determination of Zn(II) in the water samples by using graphite furnace atomic absorption spectrometry (GFAAS). 1-(2-Pyridylazo)-2-naphthol (PAN) was used as a chelating reagent. In this work, low density organic solvent was used as an extraction solvent and no centrifugation was required in this method. A special extraction cell was designed to facilitate collection of the low density extraction solvent. The predominant parameters influencing the HLLME-FA procedure, such as solution pH, concentration of PAN, extraction and homogeneous solvent types and volumes, ionic strength, and extraction time have been optimized. Applying all the optimum conditions in the process, the detection limit of 0.1 μg/L, linear range of 0.5–200 μg/L, and the precision (RSD%, n = 10) of 5.7% were obtained for zinc. The proposed procedure showed satisfactory results for the analysis of tap water, well water and sea water.
 
 KEY WORDS: Homogeneous liquid-liquid microextraction, Flotation assistance, Zinc, Graphite furnace atomic absorption spectrometry, Water samples
 Bull. Chem. Soc. Ethiop. 2022, 36(1), 1-11. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i1.1

The design and synthesis of spinel one-dimensional multi-shelled nanostructures for Li-ion batteries.

The rational design, synthesis, and massive production of one-dimensional (1D) spinel composite oxides with multi-shelled nanostructures are critical for the realization of highly efficient energy conversion and storage. However, owing to the limitations of the synthetic methods, the 1D multi-shelled nanostructures, especially for multi-element oxides and binary-metal oxides, have been rarely fabricated. Herein, we design a facile and general method to fabricate 1D spinel composite oxides with complex architectures. It is found that the concentration of the precursor polymer PAN can control the structures of the products at optimal heating rate, including hollow nanofibers, wire-in-tube nanofibers, and tube-in-tube nanofibers. This technique could be extended to various inorganic multi-element oxides and binary-metal oxides. Moreover, numerous twin boundaries (TBs) are found to form in the Co0.5Ni0.5Fe2O4 tube-in-tube nanofibers. Benefiting from both large porosity and TBs structures, the tube-in-tube hollow nanostructures are measured to possess superior electrochemical performances with high energy and stability in lithium-ion storage.

A new dispersive micro-solid phase extraction based on rejection property method combined with FAAS for the simultaneous determination of cobalt and copper after optimisation by Box-Behnken design

ABSTRACT A new, fast and simple technique of dispersive micro-solid phase extraction based on rejection property (DMSPE-RP) combined with flame atomic absorption spectrometry (FAAS) for the simultaneous preconcentration and determination of trace amounts of cobalt and copper ions has been introduced. In this technique, 1-(2-pyridylazo)-2-naphthol (PAN) was used as a chelating agent and adsorbent. The experimental factors affecting the analytical performance of the method such as pH of the sample solution, the concentration of PAN and salting-out effect were evaluated and optimised using Box–Behnken design. Under the optimum conditions, the method exhibited linear dynamic ranges of 5.0–350.0 µg L−1 for cobalt and 5.0–500.0 µg L−1 for copper with the coefficients of determination higher than 0.997. The detection limits were 1.2 and 1.5 µg L−1 and the enrichment factors were 184.0 and 154.0 for cobalt and copper, respectively. The accuracy of the method was evaluated by the analysis of water-certified reference material (TMDA 53.3 water). The results indicated that the presented method is a good technique for the determination of target metal ions in natural water samples.

Optimization of Air-assisted Liquid–liquid Microextraction by Box–behnken Design for Spectrophotometric Determination of Palladium in Water Samples

In this research, a fast, simple and highly efficient sample pretreatment technique based on air-assisted liquid–liquid microextraction (AALLME) followed by UV−Vis spectrophotometric detection has been applied for the preconcentration and determination of palladium in water samples. 1-(2-Pyridylazo)-2-naphthol (PAN) and chloroform were used as a chelating agent and extraction solvent, respectively. Parameters affecting AALLME, including pH of sample solution, concentration of PAN, volume of extraction solvent and number of extraction cycles were studied and optimized using Box–Behnken design. Under the optimum conditions, the calibration curve was linear in the concentration range of 5–700 ng/mL with the correlation coefficient (r2) of 0.996. Detection limit, enrichment factor, intra- and inter-day precision were 0.7 ng/mL, 193, 1.3 and 1.8%, respectively. Finally, the developed method was successfully applied for the determination of trace amounts of palladium in environmental water samples.

Multi-element determination of Cd, Pb, Cu, V, Cr, and Mn in ethanol fuel samples using energy dispersive X-ray fluorescence spectrometry after magnetic solid phase microextraction using CoFe2O4 nanoparticles

In this study, multi-element determination in ethanol fuel samples using energy dispersive X-ray fluorescence spectrometry (EDXRF) combined with magnetic solid phase microextraction (MSPME) was explored. The extraction and preconcentration of Cd, Pb, Cu, V, Cr, and Mn from ethanol fuel samples using CoFe2O4 nanoparticles impregnated with 1-(2-pyridylazo)-naphthol (PAN) was carried out for posterior direct determination in the solid phase using EDXRF. Factors such as the concentration of PAN, pH value, time of extraction, and sample volume were optimized. Under the optimized conditions, linear calibration curves were obtained. The precisions for the determination of each element, expressed as relative standard deviations (RSD) of standard solutions containing 0.20 mg L−1 of Cu, Cd, Pb, Cr, V, and Mn and calculated from ten consecutive measurements, were 1.6, 2.8, 2.8, 4.0, 1.5, and 4.5%, respectively. The proposed method allowed the determination of metals with detection limits of 0.012, 0.013, 0.016, 0.012, 0.009, and 0.011 mg L−1 for Cu, Cd, Pb, Cr, V, and Mn, respectively. The method was successfully applied to the extraction and determination of Cd, Pb, Cu, V, Cr, and Mn in ethanol fuel samples.

FLOTATION-ASSISTED HOMOGENEOUS LIQUID-LIQUID MICROEXTRACTION FOR TRACE DETERMINATION OF URANIUM IN WATER SAMPLES BY ICP-MS

In this study, a novel method based on floatation assistance of homogeneous liquid-liquid microextraction (FA-HLLME), combined with inductively coupled plasma-mass spectroscopy (ICP-MS) was proposed, for the determination of trace uranium in environmental water samples. As one of the miniaturized separation and extraction techniques, homogenous liquid–liquid microextraction (HLLME) has been widely applied in the field of environmental monitoring and assessment. 1,2-pyridylazo-2-naphthol (PAN) was used as the complexing agent while toluene and methanol were selected as the extraction and homogeneous solvents, respectively. The factors that influenced the extraction efficiency for uranium determination (including pH, extraction and homogeneous solvents, concentration of PAN and NaCl, extraction time) were studied statistically. Under optimum conditions (pH=7.0, 100 mL toluene, 500 mL methanol, 6.4×10-5 mol L-1 PAN, 1.5 mol L-1 NaCl and 60 sec of extraction time), the linear dynamic range for uranium determination was 1.0-500.0 ng L-1 (R2=0.9995), with a corresponding limit of detection (LOD) of was 0.27 ng L-1. The relative standard deviation (R.S.D.) (C=50.0 ng L-1, n=9) was 1.13%, with a corresponding enrichment factor of 360 for uranium extraction. The proposed method was successfully applied for the determination of uranium in different water samples.

Flotation-Assisted Homogenous Liquid–Liquid Microextraction for Determination of Cadmium in Vegetables

ABSTRACTCadmium (Cd) is a toxic element that can damage human organs. Determination of Cd in vegetables is often difficult because of low concentration and matrix effects. A simple, fast, flotation-assisted homogenous liquid–liquid microextraction (FA-HLLME) was developed for determination of Cd in vegetables prior to flame atomic absorption spectrometry (FAAS), in which 1-(2-pyridylazo)-2-naphthol (PAN) was used as a complexing agent. The process was carried out based on fast extraction of Cd from an acetic acid sample solution in which cyclohexane was the extracting solvent. Effects of pH, type and volume of extraction and homogeneous solvents, concentration of PAN, extraction time, and ionic strength on the extraction method were optimized. Under optimum conditions, the limit of detection and preconcentration factor were 0.6 µg·L−1 and 38, respectively. The relative standard deviation was less than 3.1%. Extraction recovery was 94.3%–100.9%.

Structural and textural characteristics of surface halite crusts of a supratidal, ephemeral halite pan, South Jeddah, Red Sea Coast, Saudi Arabia

Two saline (halite and gypsum) pans have recently developed overlying lagoonal and sabkha sediments in the Şarūm area, south Jeddah, Saudi Arabia, as a result of the construction of an asphaltic road 30 years ago. Structural and textural characteristics of the halite layers reflect their formation during flooding, evaporative concentration, and desiccation stages of the ephemeral halite pan. The flooding stage textures record partial dissolution of the halite crusts, resulting in the formation of truncation surfaces, microkarst pits, pipes, and vugs. Microbial mats can flourish within dissolution vugs, despite the ambient high salinity of the brine. The evaporative concentration stage is characterized by the formation of thick, flat, halite crusts, in addition to isolated masses resembling cauliflowers, mushrooms, and platforms. The halite crusts and isolated masses consist of cumulate rafts and pyramidal hoppers, chevrons, and cornets. Agitation of the brine by waves or currents induced by wind favors the formation of rippled and clastic halite. Desiccation stage textures are represented by polygonal fractures and ridges, chaotic mud-halite filling microkarst pits and pipes, overgrowths, and displacive and efflorescent halite crystals. Field and petrographic studies and major element geochemistry of the brine indicate that the main recharge to the halite pan is from numerous seawater seepage points without direct connection to the Red Sea water or surface drainage. The results of this study provide valuable sedimentological information that could be useful in the interpretation of similar ancient halite.

Pre-concentration of uranium from water samples by dispersive liquid–liquid micro-extraction

Abstract In this study, a simple and rapid dispersive liquid–liquid microextraction (DLLME) was developed for the determination of uranium in water samples prior to high performance liquid chromatography with diode array detection. 1-(2-pyridylazo)-2-naphthol (PAN) was used as complexing agent. The effect of various parameters on the extraction step including type and volume of extraction and dispersive solvents, pH of solution, concentration of PAN, extraction time, sample volume and ionic strength were studied and optimized. Under the optimum conditions, the limit of detection (LOD) and preconcentration factor were 0.3 μg L−1 and 194, respectively. Furthermore, the relative standard deviation of the ten replicate was <2.6%. The developed procedure was then applied to the extraction and determination of uranium in the water samples.

Application of cuckoo optimization algorithm–artificial neural network method of zinc oxide nanoparticles–chitosan for extraction of uranium from water samples

In this study, a solid phase extraction using the new sorbent (zinc oxide nanoparticles–chitosan) has been developed for preconcentration and determination of trace amount of uranium from water samples. Hybrid modeling of cuckoo optimization algorithm–artificial neural network (COA–ANN) has been employed to develop the model for simulation and optimization of this method. The 1-(2-pyridylazo)-2-naphthol (PAN) was used as chelating agent. The pH, volume of elution solvent, mass of zinc oxide nanoparticles–chitosan, concentration of PAN, flow rate of sample and elution solvent were the input variables, while recovery of uranium was the output. At the optimum conditions, the limit of detections and enrichment factor were 0.5μgL−1 and 125, respectively for the uranium. The developed procedure was then applied to the extraction and determination of uranium from water samples.

Ultraviolet Light Induced Photocatalytic Degradation of Phthalic Anhydride Using Aeroxide P-25 and Kronos

In this work, photocatalytic degradation of phthalic anhydride using Aeroxide P-25 and kronos 7050 was performed under external UV light source. The photocatalytic activity for both of the catalysts was investigated under external UV light source. The effect of various parameters such as catalyst loading, initial concentration and initial pH of PAN on degradation was studied. The results showed that phthalic anhydride was degraded to 71 % in 4h using Aeroxide P-25 at pH 3.5 while 55 % degradation was achieved by kronos 7050 at same conditions. It was observed that 51 % degradation of PAN was achieved by photochemical route. Under UV+Visible light illumination, 83 % of degradation of PAN was achieved using (C-doped TiO2) Kronos 7000 which proved to be the best among three catalysts. In this work the kinetic model (-rA= 0.005 C A 0.825 I b ) was developed that satisfactorily described the photocatalytic degradation of phthalic anhydride across the different sets of experimental conditions and it was observed that the experimental data for different concentration of phthalic anhydride fit this equation.

Modeling of solid-phase tea waste extraction for the removal of manganese and cobalt from water samples by using PSO-artificial neural network and response surface methodology

The aim of this research was to develop a low price adsorbent with the abundant of source to remove manganese and cobalt from water samples. Tea waste solid-phase extraction coupled with flame atomic absorption spectrometry (FAAS) was used for the extraction and determination of manganese and cobalt ions. Response surface methodology (RSM) and hybrid of artificial neural network-particle swarm optimization (ANN-PSO) have been used to develop predictive models for simulation and optimization of tea waste extraction process. The pH, amount of tea waste, concentration of PAN (complexing agent), eluent volume, concentration of eluent, and sample and eluent flow rates were the input variables, while the extraction percent of Mn and Co were the output. Two approaches for their modeling and optimization capabilities were compared. The generalization and predictive capabilities of both RSM and ANN were compared by unseen data. The results have shown the superiority of ANN compared to RSM. Under the optimum conditions, the detection limits of Mn and Co were 0.5 and 0.67μgL−1, respectively. This method was applied to the preconcentration and determination of manganese and cobalt from water samples.

Vortex-assisted liquid–liquid microextraction coupled to flame atomic absorption spectrometry for lead determination: ionic liquid based microextraction using Triton X-100 as dispersant

A simple liquid–liquid microextraction termed as vortex-assisted liquid–liquid microextraction (VLLME) coupled to flame atomic absorption spectrometry for lead (Pb) determination is achieved through phase-partitioning phenomena of ionic surfactants in aqueous solution. In this procedure, the hydrophobic chelate of Pb with 1-(2-pyridylazo)-2-naphthol (PAN) was extracted into the fine droplets of 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6], while using Triton X-100 (TX-100) as dispersing medium. Several variables including [C4mim][PF6] volume, pH of sample, TX-100 volume, concentration of PAN, centrifugation time and rate were considered to be studied. At optimum experimental values of significant variables, detection limit (LOD) and the enhancement factor (EF) were observed to be 0.307 μg L−1 and 54.2, respectively. The relative standard deviation (RSD) of 10 μg L−1 Pb was 4.09%. The coexisting ions showed no obvious negative outcome on Pb preconcentration. Validation of the developed method was carried out by Pb determination in “NIST-SRM 1515 Apple leaves” standard reference material and the results were found in good agreement with the certified values. The method was applied satisfactorily for the preconcentration of Pb in acid digested samples.

Applicability of cloud point extraction for the separation trace amount of lead ion in environmental and biological samples prior to determination by flame atomic absorption spectrometry

A sensitive cloud point extraction procedure(CPE) for the preconcentration of trace lead prior to its determination by flame atomic absorption spectrometry (FAAS) has been developed. The CPE method is based on the complex of Pb(II) ion with 1-(2-pyridylazo)-2-naphthol (PAN), and then entrapped in the non-ionic surfactant Triton X-114. The main factors affecting CPE efficiency, such as pH of sample solution, concentration of PAN and Triton X-114, equilibration temperature and time, were investigated in detail. A preconcentration factor of 30 was obtained for the preconcentration of Pb(II) ion with 15.0mL solution. Under the optimal conditions, the calibration curve was linear in the range of 7.5ngmL−1–3.5μgmL−1 of lead with R2=0.9998 (n=10). Detection limit based on three times the standard deviation of the blank (3Sb) was 5.27ngmL−1. Eight replicate determinations of 1.0μgmL−1 lead gave a mean absorbance of 0.275 with a relative standard deviation of 1.6%. The high efficiency of cloud point extraction to carry out the determination of analytes in complex matrices was demonstrated. The proposed method has been applied for determination of trace amounts of lead in biological and water samples with satisfactory results.

Conductivity of solutions of poly(acrylonitrile) in dimethyl sulfoxide

The conductivity of solutions of poly(acrylonitrile) (PAN) in dimethyl sulfoxide (DMSO) is studied. Using the Raman spectroscopy method, it is found that PAN causes associates of DMSO molecules to dissociate into free molecules, as a result of which the conductivity of the solution grows. Simultaneously, PAN molecules hamper the rotation of DMSO molecules, which decreases the conductivity. There exists a critical concentration of PAN (≈5.4 vol. %) at which the rotation of DMSO molecules is hindered to the greatest extent and the conductivity drops by an order of magnitude.

A novel ionic liquid/micro-volume back extraction procedure combined with flame atomic absorption spectrometry for determination of trace nickel in samples of nutritional interest

A simple, highly sensitive and environment-friendly method for the determination of trace amount of nickel ion in different matrices is proposed. In the preconcentration step, the nickel from 10 mL of an aqueous solution was extracted into 500 microL of ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C(4)MIM][PF(6)], containing PAN as complexing agent. Subsequently, the PAN complex was back-extracted into 250 microL of nitric acid solution, and 100 microL of it was analyzed by flow injection flame atomic absorption spectrometry (FI-FAAS). The main parameter influencing the extraction and determination of nickel, such as pH, concentration of PAN, extraction time and temperature, ionic strength, and concentration of stripping acid solution, were optimized. An enhancement factor of 40.2 was achieved with 25 mL sample. The limit of detection (LOD) and quantification obtained under the optimum conditions were 12.5 and 41.0 microg L(-1), respectively. To validate the proposed methods two certified reference materials 681-I and BCR No. 288 were analyzed and the results were in good agreement with the certified values. The proposed method was successfully applied to determination of nickel in water samples, rice flour and black tea.

Comparison of tropospheric gas-phase chemistry schemes for use within global models

Abstract. Methane and ozone are two important climate gases with significant tropospheric chemistry. Within chemistry-climate and transport models this chemistry is simplified for computational expediency. We compare the state of the art Master Chemical Mechanism (MCM) with six tropospheric chemistry schemes (CRI-reduced, GEOS-CHEM and a GEOS-CHEM adduct, MOZART-2, TOMCAT and CBM-IV) that could be used within composition transport models. We test the schemes within a box model framework under conditions derived from a composition transport model and from field observations from a regional scale pollution event. We find that CRI-reduced provides much skill in simulating the full chemistry, yet with greatly reduced complexity. We find significant variations between the other chemical schemes, and reach the following conclusions. 1) The inclusion of a gas phase N2O5+H2O reaction in one scheme and not others is a large source of uncertainty in the inorganic chemistry. 2) There are significant variations in the calculated concentration of PAN between the schemes, which will affect the long range transport of reactive nitrogen in global models. 3) The representation of isoprene chemistry differs hugely between the schemes, leading to significant uncertainties on the impact of isoprene on composition. 4) Differences are found in NO3 concentrations in the nighttime chemistry. Resolving these four issues through further investigative laboratory studies will reduce the uncertainties within the chemical schemes of global tropospheric models.

Simultaneous cloud point extraction of low levels of Cd, Cr and Hg in seaweed species prior to neutron activation analysis

A one-step preconcentration cloud point extraction (CPE) method has been developed for the simultaneous determination of Cd, Cr, and Hg using a mixture of 1-(2-pyridylazo)-2-naphthol (PAN) and 1-(2-thiazolylazo)-2-naphthol (TAN) chelating agents and polyoxyethylene nonylphenylether-20 (PONPE-20) surfactant. The pH, concentration of PAN and TAN, concentration of PONPE-20, ionic strength and temperature affecting the sepa-ration were optimized. The recoveries of each of the elements under the optimum conditions of pH 8.6, [PAN/ TAN] = 1 x 10-4 M, [PONPE-20] = 0.1 % (m/v), ionic strength = 0.05 M KNO3, and temperature of 41 oC were > 98 %. The concentrations of the elements were determined by neutron activation analysis using the Dalhousie University SLOWPOKE-2 reactor (DUSR) facility. The detection limits of Cd, Cr, and Hg were 6.0, 3.6 and 1.2 ng g-1 respectively, and precision and accuracy of measurements were evaluated. The method was success-fully applied to the simultaneous determination of Cd, Cr, and Hg in fifteen Ghanaian seaweed species. Journal of Applied Science and Technology Vol. 13 (1 & 2) 2008: pp. 48-54

Solidified floating organic drop microextraction (SFODME) for simultaneous separation/preconcentration and determination of cobalt and nickel by graphite furnace atomic absorption spectrometry (GFAAS)

Solidified floating organic drop microextraction (SFODME), combined with graphite furnace atomic absorption spectrometry (GFAAS) was proposed for simultaneous separation/enrichment and determination of trace amounts of nickel and cobalt in surface waters and sea water. 1-(2-Pyridylazo)-2-naphthol (PAN) was used as chelating agent. The main parameters affecting the performance of SFODME, such as pH, concentration of PAN, extraction time, stirring rate, extraction temperature, sample volume and nature of the solvent were optimized. Under the optimum experimental conditions, a good relative standard deviation for six determination of 20 ng l −1 of Co(II) and Ni(II) were 4.6 and 3.6%, respectively. An enrichment factor of 502 and 497 and detection limits of 0.4 and 0.3 ng l −1 for cobalt and nickel were obtained, respectively. The procedure was applied to tap water, well water, river water and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments.