A sensitive spectrophotometric method for lead determination by flow injection analysis with on-line preconcentration

A new flow injection (FI) system for the determination of Pb(II) at trace level with a preconcentration step and spectrophotometric detection is proposed. It is based on preconcentration of lead ions on chitosan and dithizone-lead complex formation in aqueous medium (pH 9). The chemicals and FIA variables influencing the performance of the system were optimized and applied to the determination of lead in natural, well, and drinking water samples. It is a simple, highly sensitive, and low cost alternative methodology. The method provided a linear rage between 25 and 250 μg l-1, a detection limit of 5.0 ng ml-1 and a sample throughput of 15 h-1. The obtained results of spiked samples are in good agreement between the proposed method and ICP-AES.Fil: Di Nezio, Maria Susana. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Palomeque, Miriam Edid. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Fernández Band, Beatriz Susana. Universidad Nacional del Sur. Departamento de Química; Argentin

Cloud-point extraction/preconcentration on-line flow injection method for mercury determination

A cloud-point extraction/preconcentration (CPE/P) step is incorporated on-line into a flow injection system which is used to determine low levels of Hg(II) added to natural water samples. The analyte is complexed with dithizone. A solid reagent column (SRC) is used to prepare the reagent on-line by using 5% (v/v) Triton X-100 solution as solvent. The CPE/P is carried out by using the non-ionic surfactant Triton X-100. After obtaining the cloud-point on-line, the surfactant-rich phase containing the complex is collected in a mini column packed with cotton wool. Then, a hot water stream is passed through the column to elute the complex and the absorbance is measured at 500nm. All the flow and chemical variables are optimized and the enhancement factor for the system is estimated. The calibration is linear over the range 0.05-0.5μgml -1, the R.S.D. is 4.8%, the limit of detection (signal:noise = 3) is 0.014μgml-1 and the sample throughput is 30h-1. An open/closed system is used to eliminate the interference of iron(III). © 2003 Elsevier B.V. All rights reserved.Fil: Garrido, Mariano Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Lista, Adriana Guillermina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Palomeque, Miriam Edid. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

An innovative micrometric granular graphite–glass system composite electrode “ready to use” in voltammetry techniques

A low cost composite electrodes employing tellurite oxide, vanadium oxide and micrometric granular graphite (NWE), were designed as an alternative to be used as working electrode in voltammetry techniques. The synthesis of these composite electrodes is carried out easily; in a short time and their surface not require previous preparation. X-ray diffraction, X-ray fluorescence spectrometry and optical microscopy studies were used to determine the morphology and chemical composition of these electrodes. The conductivity characterization was conducted with impedance and electrochemical measurements. The electrochemical properties of NWE were studied using potassium hexacyanoferrate (II) and ascorbic acid system.Fil: Pierini, Gastón Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Presa, Jimena Mailén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Frechero, Marisa Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Centurión, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

Density functional theory model for carbon dot surfaces and their interaction with silver nanoparticles

Density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were performed to represent carbon dots surfaces. The addition of different oxygen functional groups to the aromatic carbon core structure and the stability in the interaction with silver nanoparticles was also investigated. Adsorption energies were evaluated in order to compare the competition for adsorption sites on silver surface with D-glucose and D-gluconate ion molecules. The –COOH and –COO groups and the interaction of the latter with silver were proposed to explain some features of the UV–visible absorption spectra, which could also contribute to an explanation for the charge observed on carbon dot surfaces.Fil: Ambrusi, Rubén Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Arroyave Rodriguez, Jeison Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Centurión, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Pistonesi, Marcelo Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Pronsato, Maria Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentin

Simple One-Step Synthesis of Bismuth Nanoparticles for Voltammetric Sensing of Metal Ions

This study describes a simple and rapid bismuth nanoparticles (BiNPs) synthesis performed at room temperature and alkaline medium. A natural product such honey was used as a stabilizing agent. The nanoparticles were characterized with UV–Vis spectroscopy, transmission electron microscopy, zeta potential and X-ray diffraction and electrochemistry. The average size of the BiNPs were smaller than 4 nm. A glassy carbon electrode was modified with the bismuth nanoparticles by drop-casting technique showing an excellent adhesion on the electrode surface that allows several consecutive measurements. The voltammetric study of the modified electrode was carried out using Square Wave Anodic Stripping Voltammetry technique (SWAV) to quantify lead and cadmium. The SWAV parameters were optimized by Box–Behnken experimental design combined with a desirability function. The concentration ranges were 1.0 to 30.0 μg L−1 for lead and 2.0 to 30.0 μg L−1 for cadmium, and the detection limits (LDD) were 0.73 μg L−1 and 1.81 μg L−1 for lead and cadmium respectively. Water samples from the Colorado River, Argentina, were analyzed and the obtained recovery values were between 105.3–106.7% (Pb) and 88.6–102.9% (Cd). The proposed method is suitable for the determination of metals in water samples due to its versatility. Moreover, it is fast and low cost.Fil: Aguilera, Ángela Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Krepper, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

Adsorptive square wave voltammetric determination of amitraz in Argentine honeys with a microwave-assisted sample treatment

The main goal of this work is the development of an electroanalytical method for the amitraz determination in honey samples by quantification its final metabolite, 2,4 dimethylaniline. An electrochemically activated glassy carbon electrode (AGCE) as working electrode and adsorptive square wave voltammetry (ASWV) technique were used. A simple and fast microwave-assisted pretreatment of the samples was presented to accelerate the amitraz hydrolysis to 75 s. The ASWV parameters were optimized based on a “Box-Benkhen” design. The ASWV response was linear in the hydrolyzed amitraz concentration range from 0.25 to 2.50 μM with a limit of detection (LOD) of 0.19 μM. The proposed method is a simple and low-cost alternative for the determination of amitraz residues in Argentine honeys samples. Recovery experiments were performed using spiked honey samples with recoveries from 91.41 to 108.6%.Fil: Krepper, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Pistonesi, Marcelo Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

Flow-injection spectrophotometric method with on-line photodegradation for determination of ascorbic acid and total sugars in fruit juices

This article reports a flow-injection spectrophotometric determination (FIA) with a photodegradation step to determine ascorbic acid and total sugars. The flow-injection system includes a simple ultraviolet photoreactor for the on-line photodegradation. The method is based on the determination of ascorbic acid at 300. nm before the photodegradation step, followed by UV irradiation and measurement of total sugars at 268. nm. The proposed method was used to determine ascorbic acid and total sugars in commercial and natural fruit juice samples. The method was validated by using spiked samples with recoveries in the range 96.4-108.3% for ascorbic acid, and 91.0-113.2% for total sugars. © 2010 Elsevier Inc.Fil: Llamas, Natalia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

Synthesis and Characterization of Silver Nanoparticles Prepared with Honey: The Role of Carbohydrates

Silver nanoparticles were synthesized using honey at pH 5.0 and 10.0 using a rapid, low cost, and simple technique. The influence of the honey carbohydrates (glucose and fructose) in the synthesis was characterized. Moreover, the kinetic variables in the synthesis at room temperature and at pH 5.0 and 10.0 were analyzed by measuring surface plasmon resonance at 411 nm by absorption spectroscopy. Transmission electron microscopy, thermal gravimetric analysis, and differential thermal analysis were used to characterize the metal nanoparticles and the capping agents. The synthesized nanoparticles were obtained for the first time at pH 5.0. This fact allows evaluating the kinetics and reaction mechanism. The obtained nanoparticles were spherical, monodispersed, and smaller than 20 nm. The results show that glucose serves as a reducing and capping agent while fructose has a limited reducing effect.Fil: González Fá, Alejandro Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Juan, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

Automated turbidimetric determination of cyclamate in low calorie soft drinks and sweeteners without pre-treatment

A flow injection turbidimetric method for determination of cyclamate in low calorie soft drinks and sweeteners without pre-treatment is proposed. It was based on the oxidation of the sulphamic group of cyclamate, to sulphate by addition of nitrite. Then, a precipitate of sulphate was obtained by reaction with barium chloride, in presence of poly(vinyl alcohol) (PVA) in perchloric acid solution, at 30°C. The analytical signal was measured at 420 nm. The method presented a linear range between 0.015 and 0.120% (w/v) and the calibration graph was S = (7.792 ± 0.179) X - (0.114 ± 0.012), R2 = 0.999. A reproducibility of 5.9% was obtained from nine calibration graphs that were carried out on different days and with different conditions (standard solution, reagents solution, etc.). The detection and quantification limits were 0.006 and 0.02% (w/v), respectively, the sample throughput 45 h-1 (by considering the wash cycle and the time consuming to eliminate the clean solution from the system). The obtained results were agreement with that obtained with the standard method.Fil: Llamas, Natalia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin

On the mechanisms of dissolution of montroydite [HgO(s)]: Dependence of the dissolution rate on pH, temperature, and stirring rate

The dissolution behavior of montroydite (HgO) has been studied using a fully automated system. Dissolution data under equilibrium conditions are in agreement with previously published data and indicate that HgO solubility is relatively high and constant between pH 4 and 10.1 and increases markedly at pH < 4. The dissolution rate also has similar behavior: it is relatively high and constant between pH 4 and 10.1 and increases sharply at pH < 4. The dissolution process obeys a three-dimensional contraction or attrition mechanism. The dissolution rate increases with increasing temperature and stirring rate and is the result of mixed transport and reaction control. The rate of HgO dissolution is considerably higher than that of other divalent metal oxides at low pH. This high rate is due to the ability of Hg(II) to rapidly exchange its ligands. Data suggest that montroydite will only occur in nature in highly contaminated sites and indicate that Hg oxidation products that are formed at the liquid Hg/water interface may dissolve rapidly.Fil: Hocsman, Ana. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Di Nezio, Maria Susana. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Charlet, Laurent. University of Grenoble; FranciaFil: Avena, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentin