Determination of trace uranium (VI) using its self-assembly with a tetradentate–monodentate ditopic ligand by resonance light scattering

We describe here a resonance light scattering (RLS) method for uranium (VI) detection by using phosphorylethanol-amido-salophen (PAS) as optical probe. PAS is a tetradentate–monodentate ditopic ligand in which the tetradentate and monodentate ligands are salophen moiety and phosphate group, respectively. PAS can chelate uranyl with its salophen moiety. The chelated uranyl can connect phosphate group in another PAS through coordination reaction. This causes the self-assembly of PAS with uranyl to form a metallo-supramolecular polymer, resulting in a production of strong RLS signal. The RLS method was established based on the self-assemble. The RLS intensity is linearly related to the concentration of uranium (VI) in the 0.8–32 ng mL^?1 range, with a detection limit of 0.24 ng mL^?1 detection limit under optimal conditions. The method was successfully applied to determine uranium (VI) in environmental water samples with the recoveries between 97.1% and 102.6%.     

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.     

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.     

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 and Recovery of UO2(??) from Water Samples Using 2,2′‐Diamino‐4,4′‐bithiazole as a New Reagent for Solid Phase Extraction

A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of uranyl as its 2,2′‐diamino‐4,4′‐bithiazole (DABTZ) complex by using octadecylsilica columns and spectrophotometry is presented. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of DABTZ, type and least amount of eluent for elution of uranyl complex from columns, break‐through volume and limit of detection were evaluated. Also the effects of various cationic and anionic interferences on percent recovery of uranyl were studied. Average extraction efficiency of ca. 90% was obtained by elution of the column with minimal amount of solvent in the presence of interferences. The average preconcentration factor, 136 and a detection limit 0.32 ng·mL^?1 were obtained. The method was applied to the recovery and determination of uranyl in different water samples.     

Separation and chromium speciation by single-wall carbon nanotubes microcolumn and inductively coupled plasma mass spectrometry

Microcolumn packed single-walled carbon nanotubes (SWCNTs) were used as solid phase extraction adsorbent for chromium speciation coupled to inductively coupled plasma mass spectrometry for detection. The effects of the experimental parameters, including pH of the solution, sample flow rate, volume and concentration of eluent, sample volume and interfering ions, on separation and determination of Cr(III) and Cr(VI) were investigated in detail. It was found that Cr(III) was selectively sorbed on the microcolumn packed with SWCNTs in the pH range from 2.0 to 4.0, while Cr(VI) remained in solution. The retained Cr(III) was subsequently eluted with 2.0 mL of 1.2 mol L^?1 nitric acid. Under the optimum conditions, the detection limits based on 3σ criterion were 0.01 ng mL^?1 and 0.024 ng mL^?1 for Cr(III) and Cr(VI), respectively. The relative standard deviations were less than 5.0% (n?=?9, c?=?1.0 ng mL^?1). The method was successfully applied to the speciation of chromium in real samples including natural and waste water. The recoveries of spiked samples were higher than 92.5%.     

Adsorptive Cathodic Stripping Voltammetric Determination of Uranium(VI) in Presence of N‐Phenylanthranilic Acid

N‐Phenylanthranilic acid was used as a complexing agent for determination of uranium(VI) by adsorptive cathodic stripping voltammetry. Under the optimal experimental conditions of the experimental parameters, the peak current was proportional to the concentration of U(VI) in the range 0.75–30 ng mL^?1 and the detection limit was 0.036 ng mL^?1. The influence of possible interferences was investigated. The method was applied for determination of uranium in waste water from uranium conversion facility and natural water samples. Application of the method for simultaneous determination of U(VI) and Cu(II) showed that these ions could be simultaneously determined in a single scan at relatively wide concentration range.     

Optimization of Continuous Flow Hydride Generation Inductively Coupled Plasma Optical Emission Spectrometry for Sensitivity Improvement of Bismuth

Experimental variables in continuous flow hydride generation inductively coupled plasma-optical emission spectrometry (CF-HG-ICP-OES) were optimized for determination of bismuth. Concentrations of NaBH₄, HCl, and NaOH, flow rates of NaBH₄, sample solution, waste and carrier argon, radio frequency power, lengths of reaction, and stripping coils were optimized to obtain lower detection limits. Under optimum conditions, the detection limit was calculated as 0.16 ng mL^?1, and the calibration plot was linear between 1.0–50.0 ng mL^?1. An improvement in detection limit of 5.75 times by CF-HG-ICP-OES was reached vs. ICP-OES. Relative standard deviation (RSD) for ten replicate measurements of 10.0 ng mL^?1 Bi was calculated as 3.9%. Effect of possible interferic ions on Bi signal was evaluated. Accuracy of method was verified by using a standard reference material, SRM 1643e. Results found for Bi were in satisfactory agreement with certified values. The proposed method was then employed to determine trace concentration of Bi in milk samples. Bi amounts in samples were found in the range from lower than the quantitation limit to 14.5 ng mL^?1, whereas Bi concentrations were lower than the detection limit in three 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.     

Magnetic Nanoparticle-Based Micro-Solid Phase Extraction and GC�CMS Determination of Oxadiargyl in Aqueous Samples

A new facile, rapid, inexpensive, and sensitive method based on magnetic micro-solid phase extraction (M-??-SPE) coupled to gas chromatography?Cmass spectrometry (GC?CMS) was developed for determination of the herbicide oxadiargyl in environmental water samples. The feasibility of employing non-modified magnetic nanoparticles (MNPs) as sorbent was examined and applied to perform the extraction process. Influential parameters affecting the extraction efficiency along with desorption conditions were investigated and optimized. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) of the method under optimized conditions were 0.005 and 0.030 ng mL^?1, respectively. The relative standard deviations (RSD) (n = 3) at a concentration of 0.10 ng mL^?1 was 11%. The calibration curve of oxadiargyl showed linearity in the range of 0.050?C0.50 ng mL^?1. The developed method was successfully applied to the extraction of oxadiargyl from spiked tap water and Zayande-Rood River water samples and the relative recoveries of 98 and 94% were obtained, respectively.     

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.     

Sulfur modified with 2-mercaptobenzoxazole as a new sorbent for preconcentration of silver prior to determination by flame atomic absorption spectrometry

A solid-phase extraction method for preconcentration of silver and consequent determination by atomic absorption spectrometry is described. The method is based on the retention of silver on sulfur modified with 2-mercaptobenzoxazole. The retained silver is eluted from the column with a thiourea solution and determined by flame atomic absorption spectrometry. The preconcentration conditions such as pH, amount of reagent loaded on sorbent, type of eluent and its volume, flow rate and interfering ions were investigated. The calibration graph was linear in the range of 3–200 ng mL^?1 of Ag⁺ in the initial solution with r = 0.9985. The limit of detection based on 3S_b was 1.0 ng mL^?1. The relative standard deviation for ten replicate measurements of 50 and 150 ng mL^?1 of Ag⁺ was 4.1 and 1.4 %, respectively. The method was applied to the determination of silver in radiology film and 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.     

On the Effect of Hydrogen Peroxide on the Flow‐Injection Determination of Platinum Based on Luminol Chemiluminescent Reaction

Abstract

A flow‐injection chemiluminescent (CL) method for the determination of trace amounts of Pt(IV) based on the oxidation reaction of luminol in alkaline solution is proposed. The effect of Pt(IV) on the oxidation of luminol was studied in the absence and in the presence of hydrogen peroxide. The positive effect of hydrogen peroxide as well as chloride ions on the sensitivity of measurements was observed. The developed method is characterized by a low limit of detection of Pt (LOD=0.06 ng mL^?1) and good reproducibility (RSD=2.2%). The addition of hydrogen peroxide to the reaction medium resulted in decreasing of platinum detection limit to 0.03 ng mL^?1.     

Cloud point extraction and simultaneous spectrophotometric determination of V(V), Co(II) and Cu(II) ions in water samples by 5-Br-PADAP using partial least squares regression

In this work, a new method has been proposed to simultaneously determine V(V), Co(II) and Cu(II) ions from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression (PLS). The metal ions in 10 ml of aqueous solution (containing 0.2 M sodium acetate buffer solution, pH 3.5) were formed complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Then, Triton X-114 (2 %, v/v) was added to the solution. By increasing the temperature of the solution up to 55 °C, a phase separation occurred. After centrifugation at 3,000 rpm for 10 min, the surfactant-rich phase was dissolved and diluted to 0.5 mL with ethanol. The metal ions were then determined using spectrophotometry. At these optimal extraction and operating conditions, linearity was obeyed in the range 7–300, 3–100 and 15–700 ng mL^?1 of V(V), Co(II) and Cu(II), with the detection limit of 2.2, 1.0 and 4.5 ng mL^?1, respectively. The relative predictive error for the simultaneous determination of 15 test samples of different concentrations of V(V), Co(II) and Cu(II) was 3.28, 3.64 and 4.04 %, respectively. The root mean square error of prediction for applying the PLS method to 15 synthetic samples in the linear ranges of these metal ions was 3.4, 1.6 and 18.1 ng mL^?1. The interference effect of some anions and cations was also tested. The proposed method has been applied successfully to the simultaneous determination of V(V), Co(II) and Cu(II) ions in real matrix samples with the recoveries of 96.75–104.80 %.     

Solid Phase Extraction of Uranium by Naphthalene‐Methyltrioctylammonium Chloride and Arsenazo(III) Adsorbent and Subsequent Spectrophotometric Determination

A simple and effective method has been presented for the preconcentration of uranium by solid phase extraction. For this purpose arsenazo(III) supported on naphthalene‐methyltrioctylammonium chloride was used as an adsorbent and uranium solution at pH 3.5 with flow rate of 1 mL·min⁻¹ was passed through the column. Therefore, uranium‐arsenazo(III) complex was formed onto column. Uranium was quantitatively eluted with 5 mL of a 0.1% ammonium tetraphenylborate and determined by spectrophotometric method at 652 nm. Several parameters such as pH, amount of reagents, sample volume, etc. were investigated. The effect of diverse ions on the preconcentration has also been studied and the optimized conditions developed have been utilized for the trace determination of uranium. A preconcentration factor of 100 was achieved. The relative standard deviation (N=8) was 0.5% for 3 ng· mL⁻¹ of uranium. The three sigma detection limit (36) was 0.045 ng·mL⁻¹     

LC–MS/MS Determination of Catecholamines in Urine Using FMOC-Cl Derivatization on Solid-Phase Extraction Cartridge

A method for the determination of catecholamine derivatives in human urine is proposed that includes the derivatization of target compounds on a solid-phase extraction cartridge and determination of the analytes by a UHPLC method with tandem mass-spectrometric detection. 9-Fluorenyl-methoxycarbonyl chloride was used as the derivatization agent. The limits of detection for the analytes were 2.5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-adrenaline, 5 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-octopamine, and 25 ng mL^?1 for 9-fluorenyl-methoxycarbonyl-dopamine. The proposed procedure was tested on real samples obtained from volunteers.     

Evaluation of a new multi-walled carbon nanotube paste electrode modified with Alizarin Red S for the determination of tellurium by differential pulse stripping voltammetry

A new modified carbon paste electrode based on multi-walled carbon nanotube and Alizarin Red S acts as a chelating agent for tellurium(IV) ions, is described. The electrochemical responses were found to be analytically suitable to develop a method for the determination of tellurium at low concentration levels. Under optimised operational conditions, the sensor exhibited linear behaviour in the range of 2.0–300 ng mL^?1 (correlation coefficient: 0.9982) with a detection limit of 0.45 ng mL^?1. The results indicate that the sensor is sensitive and effective for the determination of tellurium in water samples and certified reference materials.     

Simultaneous Determination of Amoxicillin and Clavulanic Acid in Dog Plasma by High-Performance Liquid Chromatography Tandem Mass Spectrometry

A rapid, sensitive, and specific high-performance liquid chromatography tandem mass spectrometric method was developed for the simultaneous determination and confirmation of amoxicillin and clavulanic acid in plasma. Plasma sample was subjected to a simple deproteinization with acetonitrile, and then the supernatant was directly diluted by water. Analysis was performed on a Phenomenex Luna C₈ reversed-phase column by detection with mass spectrometry in negative ions multiple reaction monitoring mode. A gradient elution program with 0.1% formic acid and acetonitrile was performed at a flow of 0.25 mL min^?1. There is good linearity in the range of 0.5–500 ng mL^?1 for both amoxicillin and clavulanic acid. The decision limits of amoxicillin and clavulanic acid were 0.06 ng mL^?1 and 0.08 ng mL^?1 in plasma, respectively, and the detection capabilities of two analytes were below 0.5 ng mL^?1. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The extraction recoveries of amoxicillin and clavulanic acid were between 102% and 115% in plasma at three spiked levels of 0.5, 50, and 500 ng mL^?1, with the relative standard deviations less than 15% for each analyte. The developed method was applied to pharmacokinetic studies of amoxicillin and clavulanic acid tablets in healthy beagles.     

Simultaneous derivatization and extraction of iodine from milk samples by hollow fiber liquid-phase microextraction followed by gas chromatography-electron capture detection

A simple, low-cost and sensitive method is demonstrated for derivatization and extraction of iodine from milk samples using hollow fiber liquid-phase microextraction (HF-LPME) and gas chromatography-electron capture detection. Iodide ions are converted to iodine under acidic medium and in the presence of an oxidant. The generated iodine reacted with 3-pentanone in extraction vial to give 2-iodo-3-pentanone and was extracted into 4 μL of 1-octanol located in the lumen of a hollow fiber. Organic solvent was selected using one variable at a time optimization method and the other main factors affecting derivatization and HF-LPME procedures were evaluated using a Taguchi’s L₁₆ (4⁵) orthogonal array. Under optimal conditions, the method showed low limit of detection (0.5 ng mL^?1), wide linear range (1–2,000 ng mL^?1) with good correlation coefficient (0.9997) and acceptable relative standard deviation (4.6 %, n = 5). Finally, the developed method was successfully applied for determination of iodide in real samples including infant milk formulas and cow milk with reasonable relative recoveries (99.8–110.5 %).