Simultaneous spectrophotometric determination of uranium, nitric acid and nitrous acid by least-squares method in PUREX process

Multi-wavelength linear regression spectrophotometry combined with method of least squares for simultaneous determination of uranium, nitric acid and nitrous acid in PUREX (Plutonium/URanium EXtraction) process was developed. The molar absorbance matrix was calibrated with absorbance data measured in the wavelength range of 350–500 nm for a series of standard solutions by linear least-squares regression. This method used information from the absorption spectra of U(VI)–nitrous acid–nitric acid solutions to determine U(VI), nitrous acid and nitric acid. In the range of 0.95–74.1 g/L U(VI), 5 × 10^?4–2 × 10^?3 mol/L nitrous acid and 3–5 mol/L aqueous nitric acid solution, the measuring precision for determination of U(VI), nitrous acid and nitric acid was 0.46, 4.09, and 0.68 % respectively. In the solution of 30 % TBP–kerosene, the measuring precision for determination of U(VI) and nitrous acid was 0.42 and 4.2 % respectively in the range of 0.95–74.1 g/L U(VI) and 5 × 10^?4–2×10^?3 mol/L nitrous acid. The spectrophotometric method can be valuable for monitoring and controlling of both species in PUREX process operation, thanks to its simplicity, efficiency and accuracy.     

Flow‐Injection Spectrophotometric Determination of N‐acetylcysteine in Pharmaceutical Formulations with On‐Line Solid‐Phase Reactor Containing Zn(II) Phosphate Immobilized in a Polyester Resin

Abstract

A flow‐injection spectrophotometric procedure was developed for determining N‐acetylcysteine in pharmaceutical formulations. The sample was dissolved in deionized water and 400 µl of the solution was injected into a carrier stream of 1.0×10^?2 mol l^?1 sodium borate solution. The sample flowed through a column (70 mm length×2.0 mm i.d.) packed with Zn₃(PO₄)₂ immobilized in a polymeric matrix of polyester resin and Zn(II) ions were released from the solid‐phase reactor because of the formation of the Zn(II) (N‐acetylcysteine)₂ complex. The mixture merged with a stream of borate buffer solution (pH 9.0) containing 5.0×10^?4 mol l^?1 Alizarin red S and the Zn(II)Alizarin red complex formed was measured spectrophotometrically at 540 nm. The analytical curve was linear in the N‐acetylcysteine concentration range from 3.0×10^?5 to 1.5×10^?4 mol l^?1 (4.9 to 24.5 µg ml^?1) with a detections limit of 8.0×10^?6 mol l^?1 (1.3 µg ml^?1). The relative standard deviations (RSDs) were smaller than 0.5% (n=10) for solutions containing 5.0×10^?5 mol l^?1 (8.0 µg ml^?1) and 8.0×10^?5 mol l^?1 (13.0 µg ml^?1) of N‐acetylcysteine, and the analytical frequency was 60 determinations per hour. A paired t‐test showed that all results obtained for N‐acetylcysteine in commercial formulations using the proposed flow‐injection procedure and a comparative procedure agreed at the 95% confidence level.     

Effect of silver nanoparticles concentration on the metal enhancement and quenching of ciprofloxacin fluorescence intensity

Concentration effect of silver nanoparticles (AgNPs) on the photophysical properties of ciprofloxacin (Cip) have been investigated using optical absorption and fluorescence techniques. When performed AgNPs solution was added to the Cip solution, metal-enhanced fluorescence intensity and a blue-shift of 20 nm in the maximum emission spectra of Cip has been observed. The enhanced intensity of this system is strongly dependent on the AgNPs concentration and largest at the 6.0 × 10^?6 mol L^?1. With increase of AgNPs concentration, quenching of fluorescence is observed. Stern–Volmer quenching constants have been calculated at four temperatures. The results show the quenching constants are directly correlated with temperature. It indicates the quenching mechanism is the dynamic quenching in nature rather than static quenching. From which we determined the activation energy for the quenching of Cip-AgNPs to be about 31.1 kJ mol^?1. In addition, in the presence of optimum AgNPs concentration, a sensitive fluorimetric method for the determination of ciprofloxacin at the range 5.0 × 10^?7–3.0 × 10^?5 mol L^?1 and the detection limit of 2 × 10^?8 mol L^?1 in solution is proposed.     

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.     

Sensitive Determination of Prulifloxacin by Its Fluorescence Enhancement on Terbium(III)–Sodium Dodecylbenzene Sulfonate System

Abstract

A terbium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of prulifloxacin (PUFX). It was found that SDBS significantly enhanced the fluorescence intensity of the PUFX–Tb³⁺ complex (about 13-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 290 nm and 545 nm, pH 8.0, 4.0 × 10^?5 mol L^?1 terbium(III), and 4.0 × 10^?4 mol L^?1 SDBS. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of PUFX over the range 6.0 × 10^?8 to 2.0 × 10^?6mol L^?1 with a correlation coefficient of 0.9991. The detection limit (S/N = 3) was determined as 8.5 × 10^?9 mol L^?1. This method has been successfully applied for the determination of PUFX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range, and good stability. The luminescence mechanism of the system was also discussed in detail. In the fluorescence system of PUFX–Tb³⁺–SDBS, SDBS acted not only as the surfactant but also as the energy donor.     

Photoluminescence investigation of MPA–ZnS QDs interaction with selenite ion

The interaction between water-soluble zinc sulfide quantum dots (ZnS QDs) and selenite ion was investigated by photoluminescence method. The water-soluble ZnS QDs were synthesized using a simple and fast procedure based on the co-precipitation of nanoparticles in an aqueous solution in the presence of 3-mercaptopropionic acid (MPA), as the capping agent. Fluorescence intensity for MPA–ZnS QDs, with a strong fluorescent emission at about 430 nm, decreased in the presence of selenite. The influence of the effective parameters including pH and temperature was investigated. The results showed that under the optimum conditions, the fluorescence intensity change of QDs was linearly proportional to the selenite concentration in the range 4.0 × 10^?5–7.2 × 10^?4 mol L^?1. Moreover, the quenching mechanism was discussed to be a static quenching procedure.     

Spectrophotometric Multicommutated Flow System for the Determination of Hypochlorite in Bleaching Products

Abstract

A multicommutation flow system for the spectrophotometric determination of hypochlorite in bleaching products is proposed. In this system, N,N-diethyl-p-phenylenediamine (DPD) reacts with hypochlorite, and the product was monitored at 515 nm. The analytical curve for hypochlorite was linear in the concentration range from 2.68 × 10^?5 to 1.88 × 10^?4 mol L^?1 (2–14 mg L^?1) with a detection limit of 6.84 × 10^?6 mol L^?1 (0.51 mg L^?1). The sampling rate was 45 h^?1, and a relative standard deviation of 1.4% (n = 10) was obtained. The recovery of this analyte ranged from 97.2% to 102.5%, and the results found using the proposed spectrophotometric multicommutated flow system agreed with the data obtained using a reference method (iodometric titration) at the 95% confidence level.     

Flow Injection and Batch Spectrophotometric Determination of Ibuprofen Based on its Competitive Complexation Reaction with Phenolphthalein‐β‐Cyclodextrin Inclusion Complex

Abstract

Rapid, simple, and accurate spectrophotometric method is presented for the determination of ibuprofen by batch and flow injection analysis methods. The method is based on ibuprofen competitive complexation reaction with phenolphthalein‐β‐cyclodextrin (PHP‐β‐CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of ibuprofen was measured. Ibuprofen can be determined in the range 8.0×10^?6 ?3.2×10^?4 and 2.0×10^?5?5.0×10^?3 mol l^?1 by batch and flow methods, respectively. The limit of detection and limit of quantification were 6.19×10^?6 and 2.06×10^?5 mol l^?1 for batch and 1.77×10^?5 and 5.92×10^?5 mol l^?1 for flow method, respectively. The sampling rate in flow injection analysis method was 120±5 samples h^?1. The method was applied to the determination of pharmaceutical formulations.     

Determination of Polyethylene Glycol Monoester Acrylate and Polyethylene Glycol Diester Acrylate Using Reversed-Phase High-Performance Liquid Chromatography

A procedure was developed for the determination of polyethylene glycol monoester acrylate (PEGMA) and polyethylene glycol diester acrylate (PEGDA) by reversed-phase high performance liquid chromatographic (RP-HPLC) with UV detector. Sample was well separated on an SinoChrom ODS-BP (C-18) column (200 × 4.6 mm i.d., 5 μm) with mobile phases composed of acetonitrile-phosphate buffer solution (0.05 mol · L^?1 pH = 6.86) in the ratio of 42:58 (v/v). The PEGMA and PEGDA were detected by UV detector at 205 nm, and quantitatively analyzed with an external standard of methyl acrylate. For PEGMA, the linear response ranged from 0.40 × 10^?5 mol · L^?1 to 2.00 × 10^?3mol · L^?1 (r² > 0.999), the detection limit was 0.12 × 10^?5 mol · L^?1, the recovery rate was found to be 93.4%–99.7%. For PEGDA, the linear response ranged from 0.20 × 10^?5 mol · L^?1 to 1.00 × 10^?3mol · L^?1 (r² > 0.999), the detection limit was 0.04 × 10^?5 mol · L^?1, the recovery rate was found to be 99.1% ～ 105.8%. This quantitative method can also be used in the HPLC analysis of other α,β-unsaturated esters.     

Synthesis,structural characterization and DNA-binding studies of a new cobalt (II) complex: (HAcr)<Subscript>4</Subscript>[Co(Sal)<Subscript>3</Subscript>]

A new cobalt (II) coordination compound was synthesized using proton transfer mechanism. The reaction between CoCl₂·2H₂O, Salicylic acid (H₂Sal) and acridine (Acr) gave a new coordination compound formulated as (HAcr)₄[Co(Sal)₃], which was characterized by elemental analysis, NMR, IR and UV/Vis spectroscopies. The interaction of this complex with DNA has been investigated in vitro using UV absorption, fluorescence spectroscopy, viscosity measurements and gel electrophoresis methods. The intrinsic binding constant has been estimated to be 5.8 × 10⁵ M^?1 using UV absorption. The interaction of DNA–Co (II) complex caused quenching in fluorescence. The binding constant, the number of binding site and Stern–Volmer quenching constant have been calculated to be 7.7 × 10⁴ M^?1, 1.143 and 1.5 × 10⁴ Lmol^?1, respectively. The increase in the viscosity of DNA with increasing the concentration of the Co (II) complex and the observations of other experiments suggest that the cobalt (II) complex binds to DNA by partial intercalation binding mode. Furthermore, the interaction of DNA–Co (II) complex was confirmed using gel electrophoresis studies. Moreover, molecular docking technique predicted partial intercalation binding mode for the complex.     

Determination of Benzoyl Peroxide Levels in Wheat Flour and Pharmaceutical Preparations by Differential Pulse Voltammetry in Nonaqueous Media

Abstract

Benzoyl peroxide (BP) was determined by differential pulse voltammetry (DPV) using a glassy carbon electrode in a dichloromethane‐acetic acid (1.5×10^?2 mol l^?1) solution and tetrabutyl ammonium perchlorate (0.01 mol l^?1) as the supporting electrolyte. The peak potential was ?0.045 V (vs. Ag/AgCl). There was a good linear relationship between the peak current and the benzoyl peroxide concentration in the range of 2.5×10^?6–1.0×10^?4 mol l^?1. The detection limit of the method was 2.5×10^?7 mol l^?1. The recovery was 94.8–106.0%. The samples of wheat flour and the pharmaceutical preparations for the treatment of acne vulgaris were directly detected with desired results. The reaction mechanism of benzoyl peroxide on the electrode was also discussed, which was two electrons and two protons irreversible reaction.     

A Novel Enhanced Chemiluminescence System with Ag(III) Complex for the Determination of Ofloxacin and Levofloxacin in Pharmaceutical Preparation and Biological Fluid

A novel chemiluminescence (CL) method is developed for determination of ofloxacin and levofloxacin with Ag(III) complex in H₂SO₄ solution medium. The CL intensity is proportional to drug concentration in a wider range with a correlation coefficient of 0.999. The limit of detection (s/n = 3) for ofloxacin and levofloxacin was 5.3 × 10^?9 g ml^?1 and 8.3 × 10^?9 g ml^?1, respectively, and their recoveries from urine and serum samples were in the range of 90.1–112% with the RSDs of 1.0–2.8%. The proposed method was applied for analysis of real samples with satisfactory result. The possible CL mechanism was discussed.     

Determination of Minoxidil by Bleaching the Permanganate Carrier Solution in a Flow-Based Spectrophotometric System

The determination of minoxidil (MX) with potassium permanganate as a carrier in a flow injection method is described. The detection at 550 nm was linear from 1.0 × 10^?5 to 5.0 × 10^?4 mol L^?1. The limit of detection (3σ/slope) was 8.92 × 10^?6 mol L^?1, with an analytical frequency of 32 h^?1. The proposed method was applied to commercial samples, with recoveries from 104.7 to 106.4%. Comparison with the HPLC procedure reveled relative errors from 0.48 to 1.4%, and the results agreed within a 95% confidence level.     

Monitoring of atmospheric 3H around Narora Atomic Power Station

Atmospheric tritium activity is measured regularly around Narora Atomic Power Station (NAPS) since gaseous waste, which contains tritium, is being released through a 145 m high stack at NAPS site. Atmospheric data collected during 2004–2008 shows a large variation of ³H concentration in air, fluctuating in the range of ≤0.2–91.6 Bq m^?3. Significantly, higher tritium levels were measured in samples near the site boundary (1.6 km) of NAPS compared to off-site locations. The atmospheric dilution factor was found to be in the range of 1.1 × 10^?7–7.3 × 10^?7 s m^?3. The scavenging ratio of NAPS site was found to be varying from 0.2 × 10⁴ to 14.1 × 10⁴ (Bq m^?3 rain water per Bq m^?3 air). The inhalation dose to a member of general public at different distances (1.6–30 km) from NAPS site was found to be ranged from 0.08–0.21 μSv year^?1.     

Determination of Coenzyme II Using Balofloxacin–Terbium(III) as a Fluorescence Probe by Spectrofluorometry

Abstract

A new spectrofluorometric method was developed for determination of coenzyme II. We studied the interactions between balofloxacin–terbium(III) complex and coenzyme II by using ultraviolet–visible absorption and fluorescence spectra. While balofloxacin–terbium(III) was used as a fluorescence probe, under the optimum conditions, coenzyme II could remarkably enhance the fluorescence intensity of the balofloxacin–terbium(III) complex at λ = 545 nm, and the enhanced fluorescence intensity was in proportion to the concentration of coenzyme II. Optimum conditions for the determination of coenzyme II were also investigated. The dynamic range for the determination of coenzyme II was 6.0 × 10^?8 to 6.0 × 10^?6 mol L^?1, and the detection limit (3σ/k) was 3.5 × 10^?8 mol L^?1. This method was simple, practical, and relatively free interference from coexisting substances and could be successfully applied to determination of coenzyme II in synthetic samples. The mechanism of fluorescence enhancement of balofloxacin–terbium(III) complex by coenzyme II was also discussed.     

Determination of Semicarbazide-Sensitive Amine Oxidase Activity in Blood Plasma by a Light Scattering Technique

A novel method for the determination of semicarbazide-sensitive amine oxidase (SSAO) activity in blood plasma has been developed. The method was based on the change of light scattering (LS) intensity resulting from the derivative product of the interaction of 2,4-dinitrophenylhydrazine (DNPH) with benzaldehyde produced by catalyzing of SSAO to benzylamine. In Britton-Robinson (B-R) buffer solution, the intensity of system's LS at 514.6 nm was significantly enhanced and was directly proportional to the concentration of benzaldehyde. In this method, SSAO enzyme activity is defined as the concentration of benzaldehyde (nmol) formed per mL plasma per hour. The range of determination of SSAO enzyme activity was 6.40 × 10^?3 ?0.340 nmol mL^?1 h^?1 with a detection limit of 1.92 × 10^?3 nmol mL^?1 h^?1. The relative standard deviation was 2.8–4.1% and the average recovery was 67.9% (n = 6).     

RP-LC Determination of Residual Monomers in Polycarboxylate Superplasticizers

A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer by reversed-phase high performance liquid chromatography. Seven kinds of residual monomers were quantitatively determined on a SinoChrom ODS-BP (C18) column and UV detector at 205 nm. The mobile phases which were used to determine micromolecular monomers were composed of acetonitrile and phosphate buffer solution (0.05 mol L^?1, pH = 3) in the ratio of 8:92 (v/v). While the mobile phases for long side-chain monomers testing were composed of acetonitrile and phosphate buffer solution (0.05 mol L^?1, pH = 6.5) in the ratio of 40:60 (v/v). The linear response ranged from 4.0 × 10^?6?C2.0 × 10^?3 mol L^?1. The detection limit was 0.12 × 10^?5?C0.8 × 10^?5 mol L^?1. Determination of real samples showed that relative standard deviation of high conversion rate samples was 3.1?C8.7% and standard addition recovery ratio was 91.5?C102.8%. While the relative standard deviation of low conversion rate samples was less than or close to 1% and the standard addition recovery ratio was 96.3?C103.1%.     

Electrocatalytic oxidation of methanol by ZSM-5 nanozeolite-modified carbon paste electrode in alkaline medium

Development of a novel modified electrode for electrocatalytic oxidation of methanol in order to decrease overvoltage is importance. In this paper, carbon paste electrode (CPE) was modified by ZSM-5 nanozeolite. The average diameter of used nanozeolite was 97 nm. Ni²⁺ ions were incorporated to the nanozeolite by immersion of the modified electrode in a 0.1 M nickel chloride solution. Then, electrochemical studies of this electrode were performed by using cyclic voltammetry(CV) in alkaline medium. This modified electrode was used as an anode for the electrocatalytic oxidation of methanol in 0.1 M of NaOH solution. The obtained data demonstrated that ZSM-5 nanozeolite at the surface of CPE improves catalytic efficiency of the dispersed nickel ions toward methanol oxidation. The values of electron transfer coefficient, charge-transfer rate constant, and the electrode surface coverage are obtained 0.61, 0.2342 s^?1, and 4.33 × 10^?8 mol cm^?2, respectively. Also, the mean value of catalytic rate constant between the methanol and redox sites of electrode and diffusion coefficient were found to be 2.54 × 10⁴ cm³ mol^?1 s^?1 and 1.85 × 10^?8 cm² s^?1, respectively. Obtained results from both CV and chronoamperometric techniques indicated that the electrode reaction is a diffusion-controlled process.     

Voltammetric sensing of triclosan in the presence of cetyltrimethylammonium bromide using a cathodically pretreated boron-doped diamond electrode

ABSTRACT

In the present study, a simple, cheap and sensitive electrochemical method based on a cathodically pretreated boron-doped diamond (CPT-BDD) electrode is described for the detection of triclosan with the cationic surfactant (cetyltrimethylammonium bromide, CTAB) media. The oxidation of triclosan was irreversible and exhibited an adsorption controlled process. The sensitivity of the adsorptive stripping voltammetric measurements was significantly improved with addition of CTAB. Using square-wave stripping mode, a linear response was obtained for triclosan determination in Britton-Robinson buffer solution at pH 9.0 containing 2.5 × 10^?4 M CTAB at around + 0.67 V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The method could be used in the range of 0.01–1.0 μg mL^?1 (3.5 × 10^?8–3.5 × 10^?6 M), with a detection limit of 0.0023 μg mL^?1 (7.9 × 10^?9 M). The feasibility of the proposed method for the determination of triclosan in water samples was checked in spiked tap water.     

The Host-Guest Chemistry of Proflavine with Cucurbit[6,7,8]urils

The binding of the polyaromatic guest, 3,6-diaminoacridine (Proflavine) to cucurbit[n]uril (CB[n]) where n = 6, 7 and 8 has been studied by fluorescence spectrophotometry and binding constants determined using a least squares fitting method. Titration of CB[8] into a solution of Proflavine results in a 95% decrease in fluorescence up to a CB[8] to Proflavine ratio of 2:1. From the induced fluorescence spectra a binding constant of 1.9 × 10⁷ M^? 1 was determined. When Proflavine is titrated into a solution of CB[8] a similar binding constant is calculated (1.3 × 10⁷ M^? 1). Titration of CB[6] into a solution of Proflavine yields a decrease in fluorescence of 18–20%, but no binding is observed beyond what is seen within experimental error. Finally, titration of CB[7] into a solution of Proflavine results in an increase in fluorescence (32%) and a blue-shift of the emission wavelength from 509 nm to 485 nm. From the induced fluorescence spectra a binding constant of 1.65 × 10⁷ M^? 1 was determined. From ¹H NMR it appears that the decrease in fluorescence for Proflavine with CB[6] and CB[8] is due to collisional quenching, whereas the increase in fluorescence with CB[7] may be due to rotational restriction.