Chemical modification of alumina surface by immobilization of 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide for extractive concentration of silver ions

A column, solid phase extraction (SPE), preconcentration method was developed for determination of silver by using alumina coated with 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide and determination by flame atomic absorption spectrometry. The separation/preconcentration conditions for the quantitative recovery were investigated. At pH 2, the maximum sorption capacity of Ag⁺ was 7.5?mg?g^?1. The linearity was maintained in the concentration range of 0.02–11.0?µg?mL^?1 in the final solution or 0.14–1.10?×?10^4?ng?mL^?1 in the original solution for silver. The preconcentration factor of 140 and relative standard deviation of ±1.4% was obtained, under optimum conditions. The limit of detection (LOD) was calculated as 0.112?ng?mL^?1, based on 3σ_bl/m (n?=?8) in the original solutions. The proposed method was successfully applied to the determination trace amounts of silver in the environmental samples such as tea, rice and wheat flour, mint, and real water samples.     

Determination of silver(I) ion in water samples by graphite furnace atomic absorption spectrometry after preconcentration with dispersive liquid-liquid microextraction

A method was developed for the determination of silver ion (Ag) by combining dispersive liquid-liquid microextraction preconcentration with graphite furnace atomic absorption spectrometry. Diethyldithiocarbamate was used as a chelating agent, and carbon tetrachloride and methanol as extraction and dispersive solvent. Factors influencing the extraction efficiency of Ag and its subsequent determination were studied and optimized. The detection limit is 12 ng L^?1 (3 s) with an enrichment factor of 132, and the relative standard deviation is 3.5% (n?=?7, at 1.0 ng mL^?1). The method was successfully applied to the determination of trace amounts of Ag in water samples.     

Application of organo-nanoclay as a solid sorbent for rhodium complex separation and preconcentration

An organo-nanoclay is used as a new, easily accessible, and stable solid sorbent for the preconcentration of trace amounts of rhodium ions from aqueous solution, this followed by its determination by flame atomic absorption spectrometry (FAAS). Rh(III) ion was first complexed with 2,3,5,6-tetra(2-pyridyl) pyrazine (TPPZ) at pH values between 3.0 and 4.7, and then the complex was then adsorbed onto the nanoclay. The rhodium ions were eluted from the sorbent with HCl. The rhodium in the effluent was determined by FAAS. The linear analytical range is between 0.14 ng mL^?1 and 20.0 μg mL^?1 in the initial solution, the relative standard deviation at 2.0 μg mL^?1 of rhodium is 2.6% (n?=?8), the detection limit is 0.03 ng mL^?1, and the preconcentration factor is 140. Experimental parameters including the pH, eluent type, interference by other ions and breakthrough volume were optimized. The method was applied to the determination of rhodium in water, road dust and synthetic samples.     

Thiodiethanethiol Modified Silica Coated Magnetic Nanoparticles for Preconcentration and Determination of Ultratrace Amounts of Mercury,Lead, and Cadmium in Environmental and Food Samples

A new magnetic adsorbent, 2,2′-thiodiethanethiol grafted with tetraethyl orthosilicate modified Fe₃O₄ nanoparticles, was developed for the separation and preconcentration of Hg, Pb, and Cd in environmental and food samples. The concentrations of Pb and Cd were determined by inductively coupled plasma–optical emission spectrometry; Hg was determined by cold vapor atomic absorption spectrometry. A comprehensive study on the factors affecting the extraction and desorption efficiencies was performed. Under the optimized conditions, the method was linear in the 0.01–750 ng mL^?1 range (before preconcentration) with detection limits of 4, 8, and 2 ng L^?1 for Hg, Pb, and Cd, respectively. Relative standard deviations of 2.3, 2.9, and 2.4% (concentration 50 ng mL^?1, n = 7) and high preconcentration factors of 291, 285, and 288 were also obtained for Hg, Pb, and Cd. The accuracy of the proposed method was validated by analyzing a water certified reference material with satisfactory recoveries. The method was successfully applied to the determination of the analytes in tap and mineral waters and canned tuna fish samples.     

Determination of Silver by Flame Atomic Absorption Spectrometry after Preconcentration on Naphthalene Modified with Dithizone

A solid‐phase extraction method for preconcentration of silver and consequent determination by atomic absorption spectrometry is described. The method is based on the adsorption of silver on naphthalene modified with dithizone in a column. The adsorbed silver is eluted from the column with a thiourea solution and determined by flame atomic absorption spectrometry. The adsorption conditions including pH, reagent concentration, eluent volume, flow rate and interfering ions were investigated. The calibration graph was linear in the range 10–1000 ng mL^?1 of Ag in the initial solution with r = 0.9998. The limit of detection based on 3S_b was 3.9 ng mL^?1. The relative standard deviation for ten replicate measurements of 40 and 600 ng mL^?1 of Ag was 4.4% and 0.9%, respectively. The method was applied to the determination of silver in mineral, radiology film and wound dressing samples.     

Application of modified multiwalled carbon nanotubes for palladium preconcentration and determination in water and soil samples by flame atomic absorption spectrometry

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^?1 of palladium in the initial solution and the limit of detection based on 3S_b was 0.41 ng mL^?1. The method was applied to the determination of palladium in water, wastewater and soil samples.     

β-Cyclodextrin-based polyurethane (β-CDPU) polymers as solid media for adsorption and determination of Pb(II) ions in dust and water samples

In this work, β-CD-based polyurethane copolymers (β-CDPU) have been prepared by reacting β-CD with hexamethylene diisocyanate as cross-linked agent in dry DMF. This polymer showed high selectivity for preconcentration of Pb(II) at trace level prior to its flame atomic absorption spectrometric determination. The effect of several parameters such as pH, flow rate of sample, eluent kind and volume was investigated. The adsorption behaviors and mechanisms of Pb(II) on the samples were also studied. The maximum adsorption amount of Pb(II) was 8 mg g^?1 with the preconcentration factor of 250 for Pb(II). The Langmuir isotherm was proved to describe the adsorption data better than the Freundlich isotherm and a pseudo-first-order kinetic model fits the adsorption kinetic processes well. The calibration curve was linear in the range of (3–200 ng mL^?1) with a correlation coefficient of 0.9996. The limit of detection based on three times the standard deviation of the blank was 1.15 ng mL^?1. The relative standard deviations for the determination of 10 and 100 ng mL^?1 of Pb(II) were 3.60 and 0.43 % (n = 10), respectively. The method was successfully applied to the determination of lead in some environmental samples such as Tehran and Bushehr drinking water, river water and dust samples.     

Sorption of uranium using silica gel with benzoylthiourea derivatives

Benzoylthiourea derivatives (N,N-diphenyl-N′-(3-methylbenzoyl)thiourea and diphenyl-N′-(4-methylbenzoyl)thiourea) were impregnated onto silica gel. The preconcentration of uranium(VI) from aqueous solution was investigated. Extraction conditions were optimized in batch method prior to determination by uv–visible absorption spectrometry using arsenazo(III). The optimum pH for quantitative adsorption was found as 3–7. Quantitative recovery of uranium (VI) was achieved by stripping with 0.1 mol L^?1 HCl. Equilibration time was determined as 30 min for 99% sorption of U(VI). Under optimal conditions, dynamic linear range of for U(VI) was found as 0.25–10 μg mL^?1. The relative standard deviation as percentage and detection limit were 5.0% (n = 10) for 10 μg mL^?1 U(VI) solution and 8.7 ng mL^?1, respectively. The method was employed to the preconcentration of U(VI) ions in soil and tap water samples.     

Silver modified magnetic carbon nanotubes composite as a selective solid phase extractor for preconcentration and determination of trace mercury ions in water solution

A magnetic composite of silver/iron oxides/carbon nanotubes (Ag/Fe₃O₄/CNTs) was synthesized and used as an adsorbent for the preconcentration of mercury ions in water solutions at room temperature (25°C) in this study. The silver nanoparticles were supported on the magnetic CNTs. The modification enabled the composite had not only a high adsorption capacity for mercury ions (Hg²⁺) but also the magnetic isolation properties. A fast, sensitive, and simple method was successfully developed for the preconcentration and determination of trace amount of Hg²⁺ in water using the synthesized nanocomposite as adsorbent. The mercury concentration was determined by an atomic fluorescence spectrometer (AFS). The experimental conditions such as pH value, extraction temperature, extraction time, sample volume, eluent composition and concentration, sorbent amount, and coexisting ions were investigated for the optimization. A 500 mL of sample volume resulted in a preconcentration factor of 125. When a 200 mL of sample was employed, the limit of detection for Hg²⁺ was as low as 0.03 ng mL^?1with relative standard deviation of 4.4% at 0.1 ng mL^?1 (n = 7). The ease of synthesis and separation, the good adsorption capacity, and the satisfactory recovery will possibly make the composite an attractive adsorbent for the preconcentration of ultratrace Hg²⁺ in waters.     

Determination of Lead at Trace Level Through Cloud Point Extraction and Atomic Absorption Spectrometry with Electrothermal Atomization: An Environmentally Benign Methodology

The quantification of lead in water samples is presented at the sub-ppb level through preconcentration with cloud point extraction (using Triton x-100 and eriochrome black T) and atomic absorption spectrometry with electrothermal atomization. In order to study the influence of several variables, experimental design analyses were carried out. Linearity was observed between 0.15 to 1.20 ng mL^?1 (r = 0.98), with a detection limit of 0.04 ng mL^?1 and a quantification limit of 0.15 ng mL^?1. A mean recovery of 90 ± 9% (n = 6, P = 0.05) was found; at the precision was 9% expressed as the coefficient of variation. Anions and cations that were studied did not affect the recovery of lead. Water samples of different sources were analyzed directly as well as by the standard addition method; no statistical differences were found between the two procedures. Finally, the present methodology was compared with liquid–liquid extraction of the lead-ditizone complex, using green analytical indicators proposed for this purpose.     

Sensitive quantification of uranium using cloud point extraction coupled with inductively coupled plasma-optical emission spectrometry

This article reports the utilization of cloud point extraction as a preconcentration strategy prior to U(VI) determination by inductively coupled plasma-optical emission spectrometry. Complexes of U(VI) with Cyanex-301 were preconcentrated into mixed-micellar medium using Triton X-100 and Cetylpyridinium bromide at ambient temperature. Optimal values of parameters impacting the extraction efficiency were determined. The proposed technique has linearity range of 5–200 ng mL^?1 with r = 0.99 and detection and quantification limits of 0.57 and 0.85 ng mL^?1, respectively. The method has good selectivity for U(VI) over various cations and was successfully applied to U(VI) determination in water samples with satisfactory results.     

Removal, preconcentration and spectrophotometric determination of U(VI) from water samples using modified maghemite nanoparticles

Arsenazo III modified maghemite nanoparticles (A-MMNPs) was used for removing and preconcentration of U(VI) from aqueous samples. The effects of contact time, amount of adsorbent, pH and competitive ions was investigated. The experimental results were fitted to the Langmuir adsorption model in the studied concentration range of uranium (1.0 × 10^?4–1.0 × 10^?2 mol L^?1). According to the results obtained by Langmuir equation, the maximum adsorption capacity for the adsorption of U(VI) on A-MMNPs was 285 mg g^?1 at pH 7. The adsorbed uranium on the A-MMNPs was then desorbed by 0.5 mol L^?1 NaOH solution and determined spectrophotometrically. A preconcentration factor of 400 was achieved in this method. The calibration graph was linear in the range 0.04–2.4 ng mL^?1 (1.0 × 10^?10–1.0 × 10^?8 mol L^?1) of U(VI) with a correlation coefficient of 0.997. The detection limit of the method for determination of U(VI) was 0.01 ng mL^?1 and the relative standard deviation (R.S.D.) for the determination of 1.43 and 2.38 ng mL^?1 of U(VI) was 3.62% and 1.17% (n = 5), respectively. The method was applied to the determination of U(VI) in water samples.     

A highly sensitive procedure for determination of ultra trace amounts of molybdenum by graphite furnace atomic absorption spectrometry after dispersive liquid-liquid microextraction

A simple, rapid and sensitive method is developed for selective determination of ultra trace amounts of molybdenum(V?) from different water samples. The method is based on highly efficient separation and pre-concentration of molybdenum(V?) by dispersive liquid-liquid microextraction followed by its determination with graphite furnace atomic absorption spectrometry. Ultra traces of the target ion were extracted and pre-concentrated from acidic water samples by using sodium diethyldithiocarbamate as a suitable chelating agent, and carbon tetrachloride and acetone as extraction and disperser solvents, respectively. After optimizing different parameters, including type and volume of extraction and disperser solvents, pH of test solution, extraction time, volume and concentration of the chelating agent and sample volume, an enrichment factor of 362 was obtained. The linear concentration range, limit of detection and relative standard deviation of the method were evaluated as 0.04–0.8 ng mL^?1, 0.007 ng mL^?1 and 4.5%, respectively. This method was applied successfully to the determination of molybdenum in tap water and wastewater samples.     

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

Determination of ultra traces of lead in water samples after combined solid-phase extraction–dispersive liquid–liquid microextraction by graphite furnace atomic absorption spectrometry

A solid-phase extraction coupled with dispersive liquid–liquid microextraction (DLLME) method followed by graphite furnace atomic absorption spectrometry (GFAAS) was developed for the extraction, preconcentration, and determination of ultra trace amounts of lead in water samples. Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100 mL of lead solution were first concentrated using a solid phase sorbent. The extracts were collected in 1.50 mL of THF and 18 μL of carbon tetrachloride was dissolved in the collecting solvent. Then 5.0 mL pure water was injected rapidly into the mixture of THF and carbon tetrachloride for DLLME, followed by GFAAS determination of lead. The analytical figures of merit of method developed were determined. With an enrichment factor of 1,800, a linear calibration of 3–60 ng L^?1 and a limit of detection of 1.0 ng L^?1 were obtained. The relative standard deviation for seven replicate measurements of 30 ng L^?1 of lead was 5.2 %. The relative recoveries of lead in mineral, tap, well, and river water samples at spiking level of 10 and 20 ng L^?1 are in the range 94–106 %.     

Naked magnetite nanoparticles for both clean-up and solid-phase extraction-trace determination of mercury

A new solid-phase extraction method was developed for trace determination of Hg(II) by using a small amount of naked magnetite nanoparticles as an adsorbent. The magnetite nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The adsorbed Hg(II)-dithizone complex was eluted with 1.0 mL aliquot of an acidic 1-propanol solution prior to electrothermal atomic absorption spectrometry. A huge positive effect was found on the mercury adsorption by ionic strength. Under optimized condition, a linear calibration curve was obtained for mercury in the range of 0.2–50 ng mL^?1 with relative standard deviation in the range of 0.5–2.0%. The limit of detection and enrichment factor were 0.01 ng mL^?1 and 98.3, respectively. The effects of coexisting ions were studied extensively, and a new clean-up procedure was used to remove the matrix effects by using a simple sample pretreatment step using a little amount of magnetite nanoparticles. The method was successfully applied to the determination of Hg(II) in different water and human urine samples and a commercial sodium nitrate.     

Modified Activated Carbon as Solid Phase Extraction Adsorbent for the Preconcentration and Determination of Trace As(III) in Environmental Samples by Graphite Furnace Atomic Absorption Spectrometry

A simple and selective method was developed for the preconcentration, separation, and determination of trace amounts of As(III) in an aqueous solution by solid phase extraction combined with graphite furnace atomic absorption spectrometry. Activated carbon (AC) was modified by sodium diethyldithiocarbamate (NaDDTC) and then used as a new, stable and easily prepared solid sorbent in a mini column for the extraction of As(III) in aqueous solution. Factors influencing the sorption and desorption of As(III), such as volume and concentration of eluent, sample pH, flow rate and effect of interfering ions on the recovery of As(III) have been systemically investigated. At pH 2.0 As(III) could be adsorbed quantitatively by NaDDTC‐AC, and then eluted completely with 2 mL of 3.0 mol·L^?1 HNO₃. The amount of eluted As(III) was measured using graphite furnace atomic absorption spectrometry. The detection limit of As(III) was 0.04 ng·mL^?1 with enrichment factor of 100 and the relative standard deviation (RSD, n=8) was 1.58% at 10 ng·mL^?1 level.     

Highly Selective and Sensitive Preconcentration of Mercury Ion and Determination by Cold Vapor Atomic Absorption Spectroscopy

Abstract

A simple and selective method based on a sodium dodecyl sulfate (SDS)–coated chromosorb P modified by 2‐mercaptobenzoxazole (MBO) has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CVAAS).

The mercury ions were adsorbed quantitatively on SDS‐coated chromosorb due to its complexation with MBO, while the retained Hg²⁺ ions were then stripped from the column with minimal amounts of 2 M nitric acid in acetone. The eluting solution was sent to CV‐AAS for evaluating Hg²⁺ ion content and results indicate that the calibration curve was linear for Hg²⁺ ion in the range of 0.05–85.6 ng mL^?1 and 0.09–9.6 µg mL^?1 of Hg²⁺ ions. Maximum capacity of the SDS‐coated chromosorb modified with 40 mg of the ligand was found to be 498±30 µg of mercury(II), the limit of detection was 0.01 ng mL^?1, and enrichment factors were about 300, which make it suitable it for dilute solution analysis. The method was successfully applied to the determination of Hg²⁺ ion content in real samples.     

Determination of trace molybdenum in biological and water samples by graphite furnace atomic absorption spectrometry after separation and preconcentration on immobilized titanium dioxide nanoparticles

A new method has been developed for the determination of trace molybdenum based on separation and preconcentration with TiO₂ nanoparticles immobilized on silica gel (immobilized TiO₂ nanoparticles) prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS). The optimum experimental parameters for preconcentration of molybdenum, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Molybdenum can be quantitatively retained by immobilized TiO₂ nanoparticles at pH 1.0 and separated from the metal cations in the solution, then eluted completely with 0.5 mol L^?1 NaOH. The detection limit of this method for Mo was 0.6 ng L^?1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 3.4% at the 10 ng mL^?1 Mo level. The method has been applied to the determination of trace amounts of Mo in biological and water samples with satisfactory results.     

Simultaneous preconcentration and determination of malachite green and fuchsine dyes in seafood and environmental water samples using nano-alumina-based molecular imprinted polymer solid-phase extraction

Molecular imprinted polymer for determination of malachite green (MG) and fuchsine basic (FU) dyes by spectrophotometry has been used, to develop a novel simultaneous extraction and preconcentration method. Molecularly imprinted layer-coated nano-alumina (MIP@Nano-Al₂O₃) as adsorbent was prepared by surface molecular imprinting technique, and characterised by FTIR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and thermogravimetric analysis (TGA). The method is based on simultaneous extraction of MG and FU dyes from aqueous solution by using molecularly imprinted polymer and measuring the absorbance at 617 and 546 nm for MG and FU, respectively. Parameters which affect the extraction efficiency such as pH, volume of eluent and amount of adsorbent were investigated and optimised. Linear calibration curves were obtained in the range of 2–750 ng mL^?1 for MG and 1–240 ng mL^?1 for FU under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.655 and 0.245 ng mL^?1 (n = 10) for MG and FU, respectively. The relative standard deviation (RSD) for 100 ng mL^?1 of MG and FU was 2.35 and 3.06% (n = 7), respectively. The method was applied to the simultaneous determination of the dyes in different seafood and environmental water samples.