Influence of EDTA,carboxylic acids,amino- and hydroxocarboxylic acids and monosaccharides on the generation of arsines in hydride generation atomic absorption spectrometry

The influence of EDTA, carboxylic acids, amino-and hydroxocarboxylic acids, monosaccharides and humic substances on the generation of arsines in hydride generation atomic absorption spectrometry (HGAAS) was investigated. EDTA (0.02 mol L⁻¹), ascorbic acid (0.02 mol L⁻¹) and glucose or fructose (0.2 mol L⁻¹) are useful additives for levelling sensitivities for As(III), monomethylarsonate (MMA) and dimethylarsinate (DMA). The presence of glycine, malonic, tartaric acids, BICIN and soil humin extracts leads to differences in analytical signal response between these arsenic species. An analytical application to the determination of the sum of As(III), monomethylarsonate (MMA) and dimethylarsinate (DMA) as well as the sum of toxicologically relevant hydride forming arsenic fraction As(III) + As(V) + MMA + DMA in EDTA soil/sediment extracts using continuous flow HGAAS was demonstrated. The limit of detection was 0.2 mg kg⁻¹ As. Within-day and between-day precision were in the range 3–7% and 4–10%, respectively, for arsenic contents of 0.7–25 mg kg⁻¹, with recoveries 95–103%.      

Ionic liquid promoted Diels-Alder Reaction between anthrone and maleimides

Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]⁺[Cl]⁻, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.      

Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L⁻¹) and low detection limit (0.03 μg L⁻¹), which makes it suitable for determination of PCP in water samples.      

Determination of europium by using the chemical oscillating system of Ce(IV)-KBrO<Subscript>3</Subscript>-acetone-oxalic acid-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

A sensitive and convenient method for the determination of trace europium ions using an oscillating chemical reaction involving Ce(IV) - KBrO₃ - acetone - oxalic acid - H₂SO₄ was proposed. The results indicated that the changes in oscillating period (T) was linearly proportional to the negative logarithmic concentration of Eu³⁺ (-log C) in the range of 1.41 × 10⁻⁸ ˜ 1.41 × 10⁻⁴ mol L⁻¹ (r = 0.9982) with a detection limit of 1.04 × 10⁻⁹ mol L⁻¹. The recoveries were limited to the range of 99.5% to 100.8%. Under the same conditions, other rare earth ions did not interfere with the determination of Eu³⁺. In addition, a perturbation mechanism was also discussed briefly.      

Properties of ibuprofen ion-selective electrodes based on the ion pair complex of tetraoctylammonium cation

Ibuprofen membrane electrodes based on different plasticizers: diisobutyl phthalate (DIBP), o-nitrophenyloctyl ether (o-NPOE), dioctyl sebacate (DOS) and tetraoctylammonium 2-(4-isobutylphenyl)propionate were prepared. All electrodes show: a near Nernstian slope of characteristic (58.3–60.9 mV decade⁻¹) in the measurement range (10⁻⁴–10⁻¹ mol L⁻¹), limit of detection (5.0×10⁻⁵ mol L⁻¹), really long lifetime (12 months), dependence of the electrode potential on pH (5.5–9.0), reproducibility of potential (0.6–1.2 mV) and selectivity coefficients in relation to some organic and inorganic anions. The electrodes were applied for the determination of ibuprofen in tablets by the calibration curve method and the standard addition method.      

Separation and determination of inorganic cations in beverages by capillary electrophoresis with indirect UV detection

A rapid, simple and reliable capillary electrophoresis method for the separation and quantitation of inorganic cations with indirect UV detection at 214 nm was developed. The electrolyte was: 12 mM imidazole as background absorbance provider; 5 mM malic acid and 1.0 mM 18-crown-6 ether as complexing agents; and 20% D₂O (v/v) to improve ion mobility. The pH was 4.25. The applied voltage was 22 kV at 22°C. Nine ions were completely separated and determined with correlation coefficients of 0.9979-0.9992. The relative standard deviations (RSD) were less than 0.5% for migration time and less than 5.2% for peak area (n=8). The detection limits (S/N=3) were from 0.08 mg L⁻¹ (for Na⁺) to 0.51 mg L⁻¹ (for Cu²⁺). To assess the reliability atomic absorption (AA) was also used to determine the same samples. Satisfactory results were obtained for real samples of jasmine tea drink and coconut milk.      

Determination of penicillin V potassium in pharmaceuticals and spiked human urine by chemiluminescence

A simple and selective method for penicillin V potassium (PVK) determination by chemiluminescence (CL) was developed. Oxidation of PVK by alkaline hydrogen peroxide produces CL, which is greatly enhanced by N, N-dimethyl formamide (DMF) and N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). Optimum conditions were established using luminometry. There is a linear relationship between the chemiluminescent peak height and the amount of PVK within the range 0.5–129.5 mg L⁻¹, with a detection limit of 0.2 mg L⁻¹. The coefficient of variation was 1.2% for 40 mg L⁻¹ PVK solution (n = 7). The method is very simple, has high sensitivity and good selectivity, and is usable for process control. It was successfully utilized for the determination of PVK in pharmaceuticals and spiked human urine.      

Spatial trends of petroleum hydrocarbons in water and sediments

Seasonal changes in petroleum hydrocarbons in water and streambed sediment from selected oil-related areas of Ondo State, Nigeria have been examined using gravimetric and infrared methods. The highest and lowest total petroleum hydrocarbon concentrations (TPH) in water (sediments in brackets) gravimetrically were 3.49 mg L⁻¹ (199.3) mg kg⁻¹ and 0.003 mg L⁻¹ (81.0) mg kg⁻¹ while the concentrations found by IR were 24.0 mg L⁻¹ (135.0 mg kg⁻¹) and 14.0 mg L⁻¹ (33.0 mg kg⁻¹) respectively. The two seasons were positively correlated (α = 0.01) by both methods. The TPH level was well correlated with the sediment organic carbon (OC) during both seasons. The characteristic carbonyl (C=O) vibrations at 1650 cm⁻¹ and 1700 cm⁻¹ indicate oxidation of the oil residue. The study recommends further investigation into the type of organics present to evaluate their toxicity and appropriate remediation.      

Cloud point extraction-preconcentration and flame atomic absorption spectrometric determination of low levels of zinc in water and blood serum samples

A simple, sensitive and selective flotation method is described for the preconcentration and atomic absorption spectrometric determination of zinc ion in water and blood samples. At a solution pH of 5.2, 4-(2-pyridylazo-resorcinol) and Triton X-114 were used as hydrophobic ligand and non-ionic surfactant, respectively. The chemical variables affecting the preconcentration process were optimized. Under the optimized experimental conditions, the selective preconcentration and determination of as low zinc concentration as 6.5 μg L⁻¹ can be made. The proposed method was successfully applied to the preconcentration and low-level determination of zinc in different water and blood serum samples.      

Determination of diclofenac in pharmaceuticals and urine samples using a membrane sensor based on the ion associate of diclofenac with Rhodamine B

The potentiometric response characteristics of a diclofenac selective electrode, based on ion association in different plasticizers, were compared. The sensitivity, working range, detection limit and selectivity of membrane sensors demonstrated significant dependence on the type of plasticizers. The potentiometric unit presented a linear response toward diclofenac concentrations between 1 × 10⁻⁵ − 5 × 10⁻² mol L⁻¹, with slopes of approximately 60 mV dec⁻¹, and exhibited a response time of 3 s. The potentiometric analysis of sodium diclofenac in pharmaceutical formulations was perfomed by the membrane electrode proposed and compared with the results of potentiometric titration given by the Pharmacopoeia of Ukraine.      

Cobalt(II) ion-selective electrode with solid contact

A new all plastic sensor for Co²⁺ ions based on 2-amino-5 (hydroxynaphtyloazo-1′)-1,3,4 thiadiazole (ATIDAN) as ionophore was prepared. The electrode exhibits a low detection limit of 1.5 × 10⁻⁶ mol L⁻¹ and almost theoretical Nernstian slope in the activity range 4.0 × 10⁻⁶–1 × 10⁻¹ mol L⁻¹ of cobalt ions. The response time of the sensor is less than 10 s and it can be used over a period of 6 months without any measurable divergence in potential. The proposed sensor shows a fairly good selectivity for Co(II) over other metal ions. The electrode was successfully applied for determination of Co²⁺ in real samples and as an indicator electrode in potentiometric titration of Co²⁺ ions with EDTA.      

A theoretical study of the neutral and the double-charged cation of cyclo[8]pyrrole and its interaction with inorganic anions

A theoretical study of the complexation of cyclo[8]pyrrole dication, 2, and the corresponding system in neutral form, 3, with six anionic molecules has been carried out up to the B3LYP/6–311++G(2d,2p) computational level. The effect of the water solvation has been taken into account by means of the PCM method. The gas phase results correspond to the very large interaction energies expected for the interaction of molecules of opposite charge. In all the complexes, the analysis of the electron density by means of the Atoms In Molecules (AIM) methodology shows the presence of eight intermolecular interactions between the individual molecules. The results, using the water solvent model, indicate that the 2:SO₄ ²⁻ complex is more stable than the 2:NO₃ ⁻, in agreement with experimental results.      

Determination of p-nitroaniline by the tartrate-acetone-Mn2+-KBrO3-H2SO4 double organic substrate oscillating system using non-equilibrium stationary state

This paper described the determination of p-nitroaniline in a double organic substrate oscillating system of tartrate-acetone-Mn²⁺-KBrO₃-H₂SO₄. Under the optimum conditions, temperature was chosen as a control parameter to design the bifurcation point and proposed a convenient method for determination of p-nitroaniline. Results showed that the system consisting of 3.5 mL 0.06 mol L⁻¹ tartrate, 4.0 mL 0.7 mol L⁻¹ H₂SO₄, 1.5 mL 1.5×10⁻⁴ mol L⁻¹ MnSO₄, 4.0 mL 0.4 mol L⁻¹ acetone and 7.0 mL 0.05 mol L⁻¹ KBrO₃ was very sensitive to the surrounding at 33.5°C. A good linear relationship between the potential difference and the negative logarithm concentration of p-nitroaniline was obtained to be in the range of 2.50×10⁻⁷∼3.75×10⁻⁵ mol L⁻¹ with a lower detection limit of 2.50×10⁻⁸ mol L⁻¹.      

Application of a macromolecular micellar system formed by the P123 triblock copolymer for determination of copper concentrations

This work proposes a method for determination Cu(II) concentrations, based on the formation of a copper-1-nitroso-2-naphthol complex, in the presence of micelles; formed by a triblock copolymer, made up of two blocks of polyethylene oxide (PEO), and one block of polypropylene oxide (PPO). The insoluble copper complexes, are concentrated inside the hydrophobic micelle core; formed by the PPO block. For a solution containing 0.200 mg L⁻¹ Cu(II), the proposed method had a relative standard deviation of 2.0% (n = 3); an absolute error from 0.11 to 0.39 mg L⁻¹; and a linear calibration range, from 0.200 to 0.800 mg L⁻¹. Detection and quantification limits, were 43.1 mg L⁻¹ and 144 mg L⁻¹, respectively. We show that there is excellent agreement, between the results obtained using our novel method; and those obtained using flame atomic absorption spectrometry: In the determination of Cu(II) concentrations, in Brazilian sugar-cane spirits. The proposed method, is the first to apply macromolecular micelle systems, to the determination of copper concentrations; and improves upon the results obtained using molecular surfactants. This method is environmentally friendly (since it does not use any organic solvents for extraction), and the triblock copolymer is biodegradable and non-toxic.      

RETRACTED ARTICLE: Kinetic and anion degradation products study on photocatalytic degradation of reactive orange 5 solution with phosphotungstic acid

Increasing environmental pollution caused by toxic dyes is a matter of great concern due to their hazardous nature. So it is crucial to develop processes which can destroy these dyes effectively. It has been generally agreed that reactive orange 5 (KGN) can be effectively degraded in aerated phosphotungstic acid (HPA) in a homogeneous reaction system using near-UV irradiation. In this paper, photocatalytic degradation of reactive orange 5 solutions with phosphotungstic acid was investigated, especially more attention was paid to the kinetic model and the anion degradation products. The results revealed that the photocatalytic degradation reaction of KGN with HPA in a homogenous solution can be described by Langmuir-Hinshelwood equation and Langmuir-Hinshewood kinetic model described it well. The reaction manifested the first order with lower concentration(⩽30 mg L⁻¹) with the limiting rate constant and the adsorption constant in this case being 0.8098 mg L⁻¹ min⁻¹ and 4.359 10⁻² L mg⁻¹, respectively. The degradation mechanism of KGN with HPA is different from that with TiO₂, the anion products of the two reaction systems are the same. The difference in degradation mechanism of KGN with HPA from that with TiO₂ is caused by the nature of the photocatalyst.      

Comparative studies on conventional and microwave-assisted synthesis of a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a] pyrimidines and their antimicrobial activities

Comparative studies were performed on a series of 2,4-di and 2,3,4-trisubstituted benzimidazo[1,2-a]pyrimidines, which were synthesized with conventional and microwave heating methods. In microwave irradiation method, approximately, 95–97.5% of the reaction time was increased and 1–45% yield increase was obtained. All compounds were able to inhibit the growth of the screened microorganisms in vitro with MIC values between 3.9–250 μg mL⁻¹. The highest activity was expressed by compound IIId (2,4-diphenyl-benzo[4,5]imidazo[1,2-a] pyrimidine), which has the MIC value of 3.9 μg mL⁻¹ and 31.2 μg mL^-1 for Penicillium natatum ATCC 24791 and E. faecalis ATCC 29212, respectively.      

Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH₂-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D ₀) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H⁺, e⁻, e⁻, H⁺. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) were determined potentiometrically at room temperature.      

Hollow fibre liquid phase microextraction of parabens

A hollow fibre liquid phase microextraction for gas chromatographic determination of some p-hydroxybenzoic acid esters has been developed. Chlorobenzene containing tetradecane as internal standard was used for the extraction. Optimized extraction was carried out at room temperature for 40 min in the presence of 0.4 g mL⁻¹ NaCl in the sample solution. Calibration was linear up to 30 mg L⁻¹. Correlation coefficients were 0.996–0.998. Enrichment factors were 21, 95 and 154, and detection limits were 0.20, 0.03 and 0.01 μg mL⁻¹ for methylparaben, ethylparaben and propylparaben, respectively. Reproducibility was acceptable with relative standard deviations up to 11.7%. The technique was tested for water and urine analysis.      

Preparation of SAMS-CMC-CS bipolar membrane and its application in electro-generating FeO 4 2−

The preparation of SAMS-CMC-CS bipolar membrane grafted onto CMC by SAMS was reported. The cross-section view of SAMS-CMC-CS BM were studied by SEM. FT-IR spectrum indicated that SAMS-CMC-CS BM contained-SO ₃ ⁻ ,-COO⁻ and −N=CHR functional groups. Compared with CMC-CS BM, SAMS-CMC-CS BM appears to have better mechanical strength and chemical stability in alkali solution at [OH⁻]≥9.5 mol/L, with a swelling of 55 %. The electrochemical properties of SAMS-CMC-CS BM were also studied. SAMS-CS-CMC BM not only effectively prevented FeO ₄ ²⁻ from diffusing into the cathode chamber, but also played an important role in the supply of OH⁻ consumed during the electro-generated FeO ₄ ²⁻ process.