Ivanise Gaubeur

A green and efficient procedure for the preconcentration and determination of cadmium, nickel and zinc from freshwater, hemodialysis solutions and tuna fish samples by cloud point extraction and flame atomic absorption spectrometry.

Cloud point extraction (CPE) was used to simultaneously preconcentrate trace-level cadmium, nickel and zinc for determination by flame atomic absorption spectrometry (FAAS). 1-(2-Pyridilazo)-2-naphthol (PAN) was used as a complexing agent, and the metal complexes were extracted from the aqueous phase by the surfactant Triton X-114 ((1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol). Under optimized complexation and extraction conditions, the limits of detection were 0.37μgL(-1) (Cd), 2.6μgL(-1) (Ni) and 2.3μgL(-1) (Zn). This extraction was quantitative with a preconcentration factor of 30 and enrichment factor estimated to be 42, 40 and 43, respectively. The method was applied to different complex samples, and the accuracy was evaluated by analyzing a water standard reference material (NIST SRM 1643e), yielding results in agreement with the certified values.

An environmentally friendly analytical procedure for nickel determination by atomic and molecular spectrometry after cloud point extraction in different samples

Cloud point extraction (CPE) was employed for separation and preconcentration prior to the determination of nickel by graphite furnace atomic absorption spectrometry (GFAAS), flame atomic absorption spectrometry (FAAS) or UV-Vis spectrophotometry. Di-2-pyridyl ketone salicyloylhydrazone (DPKSH) was used for the first time as a complexing agent in CPE. The nickel complex was extracted from the aqueous phase using the Triton X-114 surfactant. Under optimized conditions, limits of detection obtained with GFAAS, FAAS and UV-Vis spectrophotometry were 0.14, 0.76 and 1.5 μg L−1, respectively. The extraction was quantitative and the enrichment factor was estimated to be 27. The method was applied to natural waters, hemodialysis concentrates, urine and honey samples. Accuracy was evaluated by analysis of the NIST 1643e Water standard reference material.

An anionic resin modified by di-2-pyridyl ketone salicyloylhydrazone as a new solid preconcentration phase for copper determination in ethanol fuel samples

The adsorption of DPKSH onto anionic resin was investigated at 25 ± 1 oC and pH 12 on the basis of three kinetic models including pseudo-first order, pseudo-second order and intraparticle diffusion. Isotherm equations including Langmuir, Freundlich and Dubinin-Radushkevich (D-R) were successfully applied to model the experimental data. An anionic resin loaded with DPKSH was used in a flow system for the in-line concentration of copper prior to spectrophotometric determination. Under optimized conditions, a linear response was observed between 20 and 80 µg L-1, with limits of detection and quantification estimated at 0.5 and 1.8 µg L-1, respectively, at the 95% confidence level with an enrichment factor of 11. The relative standard deviation was estimated to be 2.6% for 32 µg L-1 Cu(II) (n = 20). The results obtained for copper determination in ethanol fuel samples agreed with those achieved by flame atomic absorption spectrometry (F AAS) at the 99% confidence level.

The interaction of an azo compound with a surfactant and ion pair adsorption to solid phases.

The adsorption of SPADNS (trisodium salt of 2-(p-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid) onto resins XAD 2, XAD 7 and silica gel was studied in the presence and in the absence of the cationic surfactant CTAB (cetyl trimethylammonium bromide). At a ratio of 2.5 CTAB to 1 SPADNS, the surfactant caused a marked increase in SPADNS adsorption. The experimental results for adsorption versus time were applied on the basis of three kinetic models (pseudo-first-order Lagergren, pseudo-second-order, and intraparticle diffusion). The interaction between CTAB and SPADNS was investigated using spectrophotometric, conductometric, and computational techniques. Theoretical results point to the formation of an ion pair between CTAB and SPADNS that influences the solution spectra, in agreement with conductometric and spectrophotometric data.

General chelating action of copper, zinc and iron in mammalian cells

The high-accuracy determination of trace metals in biological systems is a crucial step for the elucidation of their role in these systems. We investigated the influence of the most commonly used intracellular metal chelators, N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), triethylenetetramine (Trien) and N,N-diethyldithiocarbamate (DeDTC), on the concentration of Cu, Fe and Zn in mammalian cells. We analyzed the influence of the chelator type, concentration and time of exposure on cultured cells. The obtained data were used to formulate a general equation for evaluating how each metal concentration is influenced by experimental conditions. For this purpose, an analytical method was developed to determine Cu, Fe and Zn concentrations in cells using graphite furnace atomic absorption spectroscopy with low sample handling and direct injection of the solid (SSGF-AAS). We used non-adherent human lymphoma U937 cells as a model, and these cells received each chelator at different concentrations and exposure times. We used a factorial design to determine models to describe Cu, Fe and Zn concentrations in cells. Analyses using cubic equation models showed that the chelator type is the most relevant factor for the three metals. Our results suggest that chelation therapy in cultured cells changes intracellular Cu, Fe and Zn concentrations in a more complex manner than currently described in the literature. For Cu, Zn and Fe variations inside the cell, the chelator type is important, and for zinc, the time of exposure and the concentration of the chelator are also important.

Speciation of Chromium in Water Samples after Dispersive Liquid-Liquid Microextraction, and Detection by Means of High-Resolution Continuum Source Atomic Absorption Spectrometry

A newly analytical method has been developed to determine total chromium and speciation of this element in water samples through dispersive liquid-liquid microextraction combined with a high-resolution continuum source flame atomic absorption spectrometry. The most significant variables affecting complexation and extraction were optimized by using response surface methodology and univariate optimization. The best conditions for both the complexation and extraction elements in this study were: complexing agent ammonium pyrrolidine dithiocarbamate (APDC 6.0 mmol L-1); pH at 2.0 (CrVI) and at 7.0 (Cr total); NaCl (5% m/v); 1-undecanol (50 µL) and ethanol 300 (CrIV) and 275 µL (total Cr). Under optimal conditions, this method resulted in a 20-100 µg L-1 linear range for CrVI and total chromium, detection limits of 0.35 (CrVI) and 6.7 µg L-1 (total Cr), as well as enriching factor of 26 (CrVI) and 19 for total Cr. The method accuracy was carried out by using certified water reference material (NIST CRM 1643e), and the results achieved were in agreement with the certified value (t-test at a confidence interval of 95%). The method developed was applied in samples of mineral water, tap water (the recovery values ranged from 88 to 115%) and seawater.

Cadmium and Lead Determination in Freshwater and Hemodialysis Solutions by Thermospray Flame Furnace Atomic Absorption Spectrometry Following Cloud Point Extraction

Cloud point extraction was employed for the separation and preconcentration of cadmium and lead prior to the determination by thermospray flame atomic absorption spectrometry. Di-2- pyridyl ketone salicyloylhydrazone (DPKSH) was used as complexing agent and the cadmium and lead complexes were extracted from the aqueous phase by the Triton X-114 surfactant. The variables associated with the preconcentration (pH as well as DPKSH, surfactant and electrolyte concentration) were optimized by using a full factorial design with two levels, four variables and a central composite. Under the optimized conditions, a sample volume of 100 µL was introduced into a hot Ti tube at a flow rate of 0.6 mL min-1 and the integrated absorbance was measured. Calibration curves were obtained with linear ranges of 0.075-2.0 µg L−1 (Cd) and 2.5-100 µg L−1 (Pb). The detection limits of 0.04 µg L−1 (Cd) and 1.3 µg L−1 (Pb) (99.7% confidence level) were obtained. The proposed method was applied to hemodialysis solutions and water samples. The accuracy of the method was evaluated by analyzing a certified reference material (NIST CRM 1643e) and the results were in agreement with the certified values at a 95% confidence level according to t-test.

Melted Paraffin Wax as an Innovative Liquid and Solid Extractant for Elemental Analysis by Laser-Induced Breakdown Spectroscopy

This work proposes a new development in the use of melted paraffin wax as a new extractant in a procedure designed to aggregate the advantages of liquid phase extraction (extract homogeneity, fast, and efficient transfer, low cost and simplicity) to solid phase extraction. As proof of concept, copper(II) in aqueous samples was converted into a hydrophobic complex of copper(II) diethyldithiocarbamate and subsequently extracted into paraffin wax. Parameters which affect the complexation and extraction (pH, DDTC, and Triton X-100 concentration, vortex agitation time and complexation time) were optimized in a univariate way. The combination of the extraction proposed procedure with laser-induced breakdown spectroscopy allowed the precise copper determination (coefficient of variation = 3.1%, n = 10) and enhanced detectability because of the concentration factor of 18 times. A calibration curve was obtained with a linear range of 0.50-10.00 mg L-1 (R2 = 0.9990, n = 7), LOD = 0.12 mg L-1, and LOQ = 0.38 mg L-1 under optimized conditions. An extraction procedure efficiency of 94% was obtained. The accuracy of the method was confirmed through the analysis of a reference material of human blood serum, by the spike and recovery trials with seawater, tap water, mineral water, and alcoholic beverages and by comparing with those results obtained by graphite furnace atomic absorption spectrometry.

Butan-1-ol as an extractant solvent in dispersive liquid-liquid microextraction in the spectrophotometric determination of aluminium

Determining aluminium ions at μg L-1 scale currently requires either costly analytical techniques such as inductively coupled plasma, and/or graphite furnace atomic absorption spectrometry. Dispersive liquid-liquid microextraction (DLLME) is designed to promote separation and preconcentration, thus making it possible to determine the analyte of interest without significant matrix influence. This study was aimed at the development of a spectrophotometric method to determine Al3+ after microextraction of its complex with quercetin. Butan-1-ol was used as a novel extractant solvent in the DLLME process. The parameters influencing complexation and microextraction, such as the amount of quercetin and volume of extractant were evaluated by univariate analysis. In optimised conditions were estimated for the proposed method: linear range from 7.5 to 165.0 μg L-1, LOD of 2.0 μg L-1, and LOQ of 7.0 μg L-1. The accuracy was checked by applying the proposed method to water (NIST SRM-1643e) and rice flour (NIST SRM-1568c) certified reference materials and spike-and-recovery trials with distinct samples (mineral water, green tea, thermal spring water, contact lens disinfecting solution, saline concentrate for hemodialysis and urine).

A novel vortex-assisted dispersive liquid-phase microextraction procedure for preconcentration of europium, gadolinium, lanthanum, neodymium, and ytterbium from waters combined with ICP techniques

A novel, simple, and rapid extraction method based on vortex-assisted dispersive liquid-phase microextraction (VA-DLPME) for the preconcentration of La, Eu, Nd, Gd and Yb in water samples combined with inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) detection is described. Butan-1-ol and 1-(2-pyridilazo)2-naphthol (PAN) were used as the extractant solvent and complexing agent, respectively. The main experimental parameters affecting the complexation and extraction of the analytes, including pH, PAN concentration, salt addition, and extractant solvent volume, were optimized. Under optimum microextraction conditions, detection limits obtained by ICP OES and ICP-MS detection were 0.3–1.1 μg L−1 and 3.0–4.0 ng L−1, respectively. The developed method was applied to water samples and a certified reference material (CRM) from the National Research Council (Coastal seawater – CASS-4). Recovery values of the rare earth elements for spiked water samples (tap water, groundwater and seawater) were 90–104% for ICP OES and 83–92% for ICP-MS. The proposed VA-DLPME procedure permits the addition of the complexing agent and extractant solvent simultaneously into the sample, avoiding the use of a centrifugation step and the use of potentially toxic solvents such as methanol and chloroform.