Sodium dodecyl sulfate coated γ-alumina support modified by a new Schiff base for solid phase extraction and flame-AAS determination of lead and copper ions

A simple and fast approach for solid phase extraction is herein described, and used to determine trace amounts of Pb2+ and Cu2+ metal ions. The solid phase support is sodium dodecyl sulfate (SDS)-coated γ-alumina modified with bis(2-hydroxy acetophenone)-1,6-hexanediimine (BHAH) ligand. The adsorbed ions were stripped from the solid phase by 6 mL of 4 M nitric acid as eluent. The eluting solution was analyzed by flame atomic absorption spectrometry (FAAS). The sorption recovery of metal ions was investigated with regard to the effects of pH, amount of ligand, γ-alumina and surfactant and the amount and type of eluent. Complexation of BHAH with Pb2+ or Cu2+ ions was examined via spectrophotometry using the HypSpec program. The detection limit for Cu2+ was 7.9 µg L-1 with a relative standard deviation of 1.67%, while that for Pb2+ was 6.4 µg L-1 with a relative standard deviation of 1.64%. A preconcentration factor of 100 was achieved for these ions. The method was successfully applied to determine analyte concentrations in samples of liver, parsley, cabbage, and water.

Flame AAS determination of metal ions in fuel ethanol after preconcentration on acid carboxymethylcellulose (CMCH)

This paper describes the preparation of acid carboxymethylcellulose (CMCH), and the results of a study on the adsorption and preconcentration (using batch and flow-through column methods) of Cd(II), Cu(II), Cr(III), Fe(III), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities for each metallic ion were (in mmol g(-1)) Cd(II) = 0.92; Cu(II) = 1.45; Cr(III) = 1.70; Fe(III) = 1.60; Ni(II) = 1.30; and Zn(II) = 1.10. By means of the flow-through method, a recovery of ca. 100% of the metallic ions adsorbed in a column packed with 2 g of CMCH was found when 5.0 mL of 1.0 mol L-1 hydrochloric acid were used as eluent. An enrichment factor of 20 (100 mt solution containing 50 mu g L-1 of the metallic ions, concentrated to 5.0 mt) was obtained by this preconcentration procedure. The sorption-desorption procedure applied allowed the development of a preconcentration and Flame AAS quantification method of metallic ions in fuel ethanol at trace levels.

Determination of metal ions in natural waters by flame-AAS after preconcentration on a 5-amino-1,3,4-thiadiazole-2-thiol modified silica gel.

5-amino-1,3,4-thiadiazole-2-thiol groups attached on a silica gel surface have been used for adsorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) from aqueous solutions. The adsorption capacities for each metal ion were (in mmol.g(-1)): Cd(II)= 0.35, Co(II)= 0.10, Cu(II)= 0.15, Fe(III)= 0.20, Hg(Il)= 0.46, Ni(II)= 0.16, Pb(II)= 0.13 and Zn(II)= 0.15. The modified silica gel was applied in the preconcentration and quantification of trace level metal ions present in water samples (river, and bog water).

Determination of cadmium in river water samples by flame AAS after on-line preconcentration in mini-column packed with 2-aminothiazole-modified silica gel

A rapid and sensitive method was developed to determine trace levels of Cd2+ ions in an aqueous medium by flame atomic absorption spectrometry, using on-line preconcentration in a mini-column packed with 100 mg of 2-aminothiazol modified silica gel (SiAT). The Cd2+ ions were sorbed at pH 5.0. The preconcentrated Cd2+ ions were directly eluted from the column to the spectrometer's nebulizer-burner system using 100 μL of 2 mol L-1 hydrochloric acid. A retention efficiency of over 95% was achieved. The enrichment factor (calculated as the ratio of slopes of the calibration graphs) obtained with preconcentrations in a mini-column packed with SiAT (A = -1.3 × 10-3 + 1.8 × 10-3 [Cd2+]) and without preconcentrations (A = 4 × 10-5 + 3.5 × 10-3[Cd2+]), was 51 and the detection limit calculated was 0.38 μg L-1. The preconcentration procedure was applied to determine trace levels of Cd in river water samples. The optimum preconcentration conditions are discussed herein.

Rapid determination of zinc in foods by flow injection analysis with flame AAS using gradient calibration method

A calibration method was developed using flow injection analysis (FI) with a Gradient Calibration Method (GCM). The method allows the rapid determination of zinc In foods (approximately 30 min) after treatment with concentrated sulphuric acid and 30% hydrogen peroxide, and analysis with flame atomic absorption spectrometry (FAAS). The method provides analytical results with a relative standard deviation of about 2% and requires less time than by conventional FI calibration. The electronic selection of different segments along the gradient and monitoring of the technique covers wide concentration ranges while maintaining the inherent high precision of flow injection analysis. Concentrations, flow rates, and flow times of the reagents were optimized in order to obtain best accuracy and precision. Flow rates of 10 mL/min were selected for zinc. In addition, the system enables electronic dilution and calibration where a multipoint curve can be constructed using a single sample injection.

Determination of Zinc in Lubricating Oil by Flame MS Employing Ultrasonic Extraction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of laser induced breakdown spectrometry for the determination of macro and micronutrients in pharmaceutical tablets

The aim of this work is to demonstrate the feasibility of laser induced breakdown spectrometry (LIBS) for the determination of macro and micronutrients in multielement tablets. The experimental setup was designed by using a laser Q-switch (Nd:YAG, 10 Hz, lambda = 1064 nm) and the emission signals were collected by lenses into an optical fiber coupled to an echelle spectrometer equipped with a high-resolution intensified charge coupled device (ICCD). Tablets were cryogenically ground and thereafter pelletized before LIBS analysis. Calibration curves were made by employing samples and mixtures of commercial multielement tablets with binders at different ratios. Best results were achieved by using the following experimental conditions: 29 J cm(-2) laser fluence, 165 mm lens to sample distance (f = 200 mm), 2.0 mu s delay time, 5.0 mu s integration time and 5 accumulated laser pulses. In general, the results obtained by the proposed LIBS procedure were in agreement with those obtained by ICP OES from the corresponding acid digests and coefficients variation of LIBS measurements varied from 2 to 16%. The metrological figures of merit indicate that LIBS fits for the intended purposes, and can be recommended for the analysis of multielement tablets and similar matrices aiming the determination of Ca, Cu, Fe, Mg, Mn, P and Zn.

Determinação de contaminantes em óleos lubrificantes usados e em esgotos contaminados por esses lubrificantes

A simple and reliable ashing procedure is proposed for the preparation of used lubricating oil samples for the determination of Zn, Fe, Pb, Ni and Cu by the flame atomic absorption spectrometry technique. Sulphanilic acid was added to oil samples, the mixture coked and the coke ashed at 550 ºC. The solutions of the ash were analysed by flame AAS for these metals. The quantification limits were 38.250 µg g-1 for Zn, 4.550 µg g-1 for Fe, 1.562 µg g-1 for Pb, 1.450 µg g-1 for Ni, and 0.439 µg g-1 for Cu. The determinations, in lubricating oil, showed good precision and accuracy with recoveries between 90 and 110 %, indicating a negligible matrix effect in the experiments using addition of analyte, with relative standard deviation lower than 5%. The results for analysis of wastewater contamined by theses lubricants showed a very high relative standard deviation.

Determination of Copper, Iron, Nickel and Zinc in fuel kerosene by FAAS after adsorption and pre-concentration on 2-aminothiazole-modified silica gel

Silica gel chemically modified with 2-Aminotiazole groups, abbreviated as SiAT, was used for preconcentration of copper, zinc, nickel and iron from kerosene, normally used as a engine fuel for airplanes. Surface characteristics and surface area of the silica gel were obtained before and after chemical modification using FT-IR, Kjeldhal and surface area analysis (B.E.T.). The retention and recovery of the analyte elements were studied by applying batch and column techniques. The experimental parameters, such as shaking time in batch technique, flow rate and concentration of the eluent (HCl- 0.25-2.00 mol L-1) and the amount of silica, on retention and elution, have been investigated. Detection limits of the method for copper, iron, nickel and zinc are 0.77, 2.92, 1.73 and 0.097 mg L-1, respectively. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in kerosene using flame AAS for their quantification.

Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis

A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.

OFFLINE AND ONLINE SOLID PHASE EXTRACTION/PRECONCENTRATION OF INORGANICS

Solid phase extraction (SPE) is a powerful technique for preconcentration/removal or separation of trace and ultra trace amounts of toxic and nutrient elements. SPE effectively simplifies the labour intensive sample preparation, increase its reliability and eliminate the clean up step by using more selective extraction procedures. The synthesis of sorbents with a simplified procedure and diminution of the risks of errors shows the interest in the areas of environmental monitoring, geochemical exploration, food, agricultural, pharmaceutical, biochemical industry and high purity metal designing, etc. There is no universal SPE method because the sample pretreatment depends strongly on the analytical demand. But there is always an increasing demand for more sensitive, selective, rapid and reliable analytical procedures. Among the various materials, chelate modified naphthalene, activated carbon and chelate functionalized highly cross linked polymers are most important. In the biological and environmental field, large numbers of samples are to be analysed within a short span of time. Hence, online flow injection methods are preferred as they allow extraction, separation, identification and quantification of many numbers of analytes. The flow injection online preconcentration flame AAS procedure developed allows the determination of as low as 0.1 µg/l of nickel in soil and cobalt in human hair samples. The developed procedure is precise and rapid and allows the analysis of 30 samples per hour with a loading time of 60 s. The online FI manifold used in the present study permits high sampling, loading rates and thus resulting in higher preconcentration/enrichment factors of -725 and 600 for cobalt and nickel respectively with a 1 min preconcentration time compared to conventional FAAS signal. These enrichment factors are far superior to hitherto developed on line preconcentration procedures for inorganics. The instrumentation adopted in the present study allows much simpler equipment and low maintenance costs compared to costlier ICP-AES or ICP-MS instruments.

Alterações ambientais em Parelhas, Rio Grande do Norte: metais pesados em sedimentos de drenagens e percepção de comunidades rurais em relação a mudanças na paisagem

The conservation of natural resources is essential and constitutes the main subject of many researches, which characterize important aspects concerning the environmental alterations in the ground, water, landscape and socioeconomic information. This study aimed to investigate the anthropogenic input of heavy metals in the environment, in the area of the Parelhas dump site and in part of the Seridó River and to determine the concentration of heavy metals in the sediments. This can result in risk to the environment and human health. In addition, we sought to establish the socioeconomic profile of rural communities adjacent to Seridó River and to comprehend the perception of these dwellers about the changes in the places they live. The area of this study is located in the city of Parelhas/RN, in the centralsouthern part of the State, in the micro-region of the Oriental Seridó. This area comprehends the place where the dump site is located, next to RN 086, the Caldeirão dam, the Quintos river called by local citizens Caldeirão creek and part of Seridó river, perpetuated by the Boqueirão dam, which crosses the city and it includes the rural communities of Almas, Domingas, Sussuarana II and Colonos. Regarding the study with bottom sediments, the samples were collected and taken to the laboratory of geochemistry, where they were dried, sieved, weighted and submitted to weak acid attack. The analysis of heavy metals was held by Atomic Absorption Spectrophotometer - Flame AAS. We applied 23 closed questionnaires constituted by 38 questions to collect informations in the rural communities, oriented to establish the socioeconomic profile and the environmental perception of the participants. The participants were distributed in the communities of Almas (1), Domingas (2), Sussuarana II (10) and Colonos (10). Most of them presented similar socioeconomic profiles. They are from 45 to 60 years old and live in these localities for 20 to 30 years or more. The families are composed by 3 or 4 people; the agriculture is the main activity, livestock is the secondary and 48% of them earn the minimal wage. Regarding the environmental perception, the participants can realize some changes in vegetation, soil, water and landscape. People living longer in the community, and with more years of experience on the local reality can perceive the depletion of the soil, pastures and changes in the landscape. These changes portray how the place was previously and what it represents today. The perception of these changes, besides the environmental ones, includes others concerning the increasing number of dwellers in the last years, as well as the number of houses. The changes happened through activities developed by the dwellers over the years, including agricultural practices, livestock, grass planting and even the cultivation of cotton. The study provided the acquisition of new data about the environmental reality of this region. It can subsidize the definition of public policies that can be implemented from the perspective of conservation of water resources and of the coexistence and survival of man in the semi-arid

Determination of copper, iron, nickel and zinc in gasoline by FAAS after sorption and preconcentration on silica modified with 2-aminotiazole groups

Silica gel chemically modified with 2-aminotiazole groups (SiAT), was used for preconcentration of cupper, zinc, nickel and iron from gasoline, normally used as a engine fuel. Surface characteristics and surface area of the silica gel were obtained before and after chemical modification using FT-IR, Kjeldhal and surface area analysis (B.E.T.). The retention and recovery of the analyte elements were studied by applying batch and column techniques. The experimental parameters, such as shaking time in batch technique, flow rate and concentration of the eluent (HCl-0.25-2.00 mol 1(-1)) and the amount of silica, on retention and elution, have been investigated. Detection limits of the method for cupper, iron, nickel and zinc are 0.8, 3, 2 and 0.1 mug 1(-1), respectively. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in gasoline using flame AAS for their quantification. (C) 2004 Published by Elsevier Ltd.

Determination of Cu, Ni, and Zn in fuel ethanol by FAAS after enrichment in column packed with 2-aminothiazole-modified silica gel

This work describes the synthesis and characterization of 2-aminothiazole-modified silica gel (SiAT), as well as its application for preconcentration (in batch and column technique) of Cu(II), Ni(II) and Zn(II) in ethanol medium. The adsorption capacities of SiAT determined for each metal ion were (mmol g(-1)): Cu(II)=1.20, Ni(II)=1.10 and Zn(II)=0.90. In addition, results obtained in flow experiments, showed a recovery of ca. 100% of the metal ions adsorbed in a column packed with 500 mg of SiAT. The eluent was 2.0 mol L-1 HCl. The sorption-desorption of the studied metal ions made possible the development of a preconcentration method for metal ions at trace level in fuel ethanol using flame AAS for their quantification.

Determinação de Cd por FAAS em meio aquoso após pré-concentração em linha sobre SiAT

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)