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Search Results: 1 - 10 of 5015 matches for " Graphite furnace atomic absorption "
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Determination of Trace Amounts of Lead by Modified Graphite Furnace Atomic Absorption Spectrometry after Liquid Phase Microextraction with Pyrimidine-2-thiol  [PDF]
Saeid Nazari
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.27087
Abstract: The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorption spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration step, lead was extracted from a 2 ml of its aqueous sample in the pH = 5 as lead-Pyrimidine-2-thiol cationic complex into a 4 µl drop of 1,2 dichloroethane and ammonium tetraphenylborate as counter ion immersed in the solution. In the drop, the lead-Pyrimidine-2-thiol ammonium tetraphenylborate ion associated complex was formed. After extraction, the microdrop was retracted and directly transferred into a graphite tube modified by [W.Pd.Mg] (c). Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time, stirring rate and effect of salt were optimized. Under the optimum conditions, the enrichment factor and recovery were 525% and 94%, respectively. The calibration graph was linear in the range of 0.01 - 12 µg?L–1 with correlation coefficient of 0.9975 under the optimum conditions of the recommended procedure. The detection limit based on the 3Sb criterion was 0.0072 µg?L–1 and relative standard deviation (RSD) for ten replicate measurement of 0.1 µg?L–1 and 0.4 µg?L–1 lead was 4.5% and 3.8% respectively. The characteristic concentration was 0.0065 µg?L–1 equivalent to a characteristic mass of 26 fg. The results for determination of lead in reference materials, spiked tap water and seawater demonstrated the accuracy, recovery and applicability of the presented method.
Investigation of Distribution for Trace Lead and Cadmium in Chinese Herbal Medicines and Their Decoctions by Graphite Furnace Atomic Absorption Spectrometry  [PDF]
Hanwen Sun, Lixin Li
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.22026
Abstract: Lead and cadmium in herbal medicines are highly toxic to living organisms even in low concentrations. An effective method is developed for analysis of trace lead and cadmium in Chinese herbal medicines and their decoctions by graphite furnace atomic absorption spectrometry (GFAAS). The effects of analytical conditions on absorbance were investigated and optimized. A water-dissolving capability for Pb and Cd was investigated, and the contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The content ratios (kow) of n-octanol-soluble Pb or Cd to water-soluble Pb or Cd were evaluated, and the distribution of Pb and Cd in water decoction at stomach and intestine acidities was developed, in the first time. The contents of water-soluble Pb and Cd, n-octanol-soluble Pb and Cd, and their content ratios were related with the kind of medicine and the acidity of the decoction. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3 σ detection limits of 4.2 pg for Pb and 0.1 pg for Cd.
Measuring Conditions for the Determination of Lead in Iron-Matrix Samples Using Graphite Atomizers with/without a Platform in Graphite Furnace Atomic Absorption Spectrometry  [PDF]
Syun Morimoto, Tetsuya Ashino, Kazuaki Wagatsuma
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.26081
Abstract: In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sample solution containing trace amounts of lead. Absorption profiles of a lead line were meas- ured at various compositions of iron and palladium. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribu- tion. Each addition of iron and palladium increased the lead absorbance in both the atomizers, indicating that iron or palladium became an effective matrix modifier for the determination of lead. Especially, palladium played a significant role for controlling chemical species of lead at the charring stage in the platform-type atomizer, to change several chemical species to a single species and eventually to yield a dominant peak of the lead absorbance at the atomizing stage. Furthermore, the addition of palladium delayed the peak after the gas atmosphere in the atomizer was heated to a higher temperature. These phenomena would be because the temperature of the platform at the charring stage was elevated more slowly compared to that of the furnace wall, and also because a thermally-stable compound, such as a palladium-lead solid solution, was produced by their metallurgical reaction during heating of the charring stage. A platform-type atomizer with palladium as the matrix modifier is recommended for the determination of lead in GF-AAS. The optimum condition for this was obtained in a coexistence of 1.0 × 10–2 g/dm3 palladium, when the charring at 973 K and then the atomizing at 3073 K were conducted.
Determination of Heavy Metals at Sub-ppb Levels in Water by Graphite Furnace Atomic Absorption Spectrometry Using a Direct Introduction Technique after Preconcentration with an Iminodiacetate Extraction Disk  [PDF]
Tetsuo Inui, Atsuko Kosuge, Atsushi Ohbuchi, Kazuhiro Fujita, Yuya Koike, Masaru Kitano, Toshihiro Nakamura
American Journal of Analytical Chemistry (AJAC) , 2012, DOI: 10.4236/ajac.2012.310090
Abstract: A direct analysis method combining an iminodiacetate extraction disk (IED) with graphite furnace atomic absorption spectrometry was developed for the determination of Co, Ni, Cu, Cd, Sn, Pb, and Bi at sub-ppb levels in water. A 100 mL water sample was adjusted to pH 5.6 with nitric acid and a 1 mol?L–1 ammonium acetate solution, and then passed through an IED (diameter, 47 mm; effective filtering diameter, 35 mm) at a flow rate of 80 - 100 mL?min–1 to preconcentrate seven analytes. The IED was dried at 100?C for 20 min in an electric oven, and 110 - 145 small disks, each 2 mm in diameter, were punched out from the IED. A small disk was introduced into the graphite furnace and atomized according to a heating program. For Cd, Sn, Pb, and Bi measurements, Pd was used as a chemical modifier to enhance the absorbances. Calibration was performed using aqueous standard solutions. The detection limits, corresponding to three times the standard deviation (n = 5) of the blank values, were 0.092 μg·L–1 for Co, 0.12 μg·L–1 for Ni, 0.40 μg·L–1 for Cu, 0.077 μg·L–1 for Cd, 0.92 μg·L–1 for Sn, 0.61 μg·L–1 for Pb, and 0.80 μg·L–1 for Bi with an enrichment factor of 140 using a 100-mL water sample. A spike test for the seven analytes in tap water, rainwater, river water, and mineral drinking water showed quantitative recoveries (93% - 108%).
Análise direta de sólidos por espectrometria de absor??o at?mica com atomiza??o em forno de grafite: uma revis?o
Nomura, Cassiana Seimi;Silva, Cíntia Soares da;Oliveira, Pedro Vitoriano;
Química Nova , 2008, DOI: 10.1590/S0100-40422008000100022
Abstract: this is a review of direct analysis using solid sampling graphite furnace atomic absorption spectrometry. greater emphasis is dedicated to sample preparation, sample homogeneity, calibration and its application to microanalysis and micro-homogeneity studies. the main advantages and some difficulties related to the applicability of this technique are discussed. a literature search on the application of solid sampling graphite furnace atomic absorption spectrometry in trace element determination in many kinds of samples, including biological, clinical, technological and environmental ones, is also presented.
Determina??o de fósforo em a?os por espectrometria de absor??o at?mica no forno de grafite
Curtius, Adilson José;
Química Nova , 1998, DOI: 10.1590/S0100-40421998000300003
Abstract: a method for the determination of phosphorus in steel samples by graphite furnace atomic absorption spectrometry, using the zeeman effect background correction and the stpf conditions is proposed. the effect of iron (iii) on the phosphorus signal was studied. it was verified, through the pyrolysis temperature curves, that iron (iii) is an efficient chemical modifier, thermically stabilizing phosphorus up to 1400oc. the phosphorus signal increases with the iron (iii) concentration, but in the range, which corresponds to the usual concentrations of iron in the sample solutions, the increase is small. phosphorus was determined in three standard reference materials, after its dissolution in a mixture of hydrochloric and perchloric acids in a ptfe bomb. the agreement with the certified concentration values was excellent. iron (iii) was added to the reference analytical solutions prepared in the blank of the dissolution, while the sample solutions were measured directly, since they already contained the modifier. the detection limit (k = 2) was 0.0042% of phosphorus in the steel sample.
Determina o de fósforo em a os por espectrometria de absor o at mica no forno de grafite
Curtius Adilson José
Química Nova , 1998,
Abstract: A method for the determination of phosphorus in steel samples by graphite furnace atomic absorption spectrometry, using the Zeeman effect background correction and the STPF conditions is proposed. The effect of iron (III) on the phosphorus signal was studied. It was verified, through the pyrolysis temperature curves, that iron (III) is an efficient chemical modifier, thermically stabilizing phosphorus up to 1400oC. The phosphorus signal increases with the iron (III) concentration, but in the range, which corresponds to the usual concentrations of iron in the sample solutions, the increase is small. Phosphorus was determined in three standard reference materials, after its dissolution in a mixture of hydrochloric and perchloric acids in a PTFE bomb. The agreement with the certified concentration values was excellent. Iron (III) was added to the reference analytical solutions prepared in the blank of the dissolution, while the sample solutions were measured directly, since they already contained the modifier. The detection limit (k = 2) was 0.0042% of phosphorus in the steel sample.
Ultra Sensitive Determination and Preconcentration of Cd2+, Cu2+ and Pb2+ after Multi-Walled Carbon Nanotubes Adsorption  [PDF]
Ashraf Mohamed Abdel-Lateef, Ramadan Abdel-Wahed Mohamed, Hazem Hassan Mahmoud
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2013, DOI: 10.4236/jasmi.2013.31002
Abstract:

Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Spectrometry and inductively coupled Plasma Optical Emission spectrometry. The method is based on the electrostatic interactions of positively charged Cd+, Cu+ and Pb+ with the negatively charged multi-walled carbon nanotubes (MWCNTs) for the preconcentration and isolation of analytes from sample solutions. Effective preconcentration of trace cadmium, copper and lead was achieved in a pH range of 5 - 7, 5 - 7 and 4 - 7, respectively. The retained cadmium, copper and lead were efficiently eluted with 0.3 mol·L-1 HCl for graphite Furnace Atomic Absorption Spectrometry determination. The multi-walled carbon nanotubes packed micro-column exhibited fairly fast kinetics for the adsorption of cadmium, copper and lead, permitting the use of high sample flow rates up to at least 3 mL·min-1 for the flow injection on micro-column preconcentration without the loss of the retention efficiency. The detection limits (3σ) were 0.03, 0.01 and 0.5 ng·mL-1 for Cd, Cu and Pb, respectively. The relative standard deviation under optimum condition is less than 2.9% (n = 10). The developed method was successfully applied to the determination of trace Cd, Cu and Pb in a variety of environmental and biological samples.

A microdigestion procedure directly performed in the autosampler cups for the determination of trace elements in biological samples by GF AAS
Campos, Reinaldo C.;Jerez Vegueria, Sergio F.;Gon?alves, Rodrigo A.;Wagener, ?ngela L. R.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009001000023
Abstract: a microdigestion procedure for the determination of cd and cu in biological samples by graphite furnace atomic absorption spectrometry (gf aas) is described. masses up to 5 mg are directly weighed in the autosampler cup and 100 μl of the digestion solution (1:1 v/v hno3-h2so4 or concentrated hno3) are added. the cups are closed and the digestion is performed, at 60 oc overnight in a specially designed digestion block. after cooling, 900 μl of ultrapure water is added, the solution is homogenized and the cups are transferred to the autosampler tray. since the digestion is performed in a sealed environment and the whole procedure uses only one flask, the risks of contamination and losses are minimized. calibration was performed with external calibration curves, in the same medium as the reagents blank. the analysis of nine different standard reference materials permitted the assessment to the accuracy of the procedure. considering a 5 mg sample mass, the limits of quantification in the original samples calculated from ten successive measurements of the blank solution (k=10) were 0.07 and 1.7 and 0.02 and 0.3 μg g-1 for cd and cu respectively, using the hno3-h2so4 mixture or concentrated hno3 for the digestion. the procedure was used for the determination of cu in human liver biopsy samples.
Optimization and validation of a methodology to determine total arsenic, As(III) and As(V), in water samples, through graphite furnace atomic absorption spectrometry
Santos, Lisia Maria Gobbo;Jacob, Silvana do Couto;
Ciência e Tecnologia de Alimentos , 2009, DOI: 10.1590/S0101-20612009000100019
Abstract: the graphite furnace atomic absorption spectrometry (gf aas) was the technique chosen by the inorganic contamination laboratory (incq/ fiocruz) to be validated and applied in routine analysis for arsenic detection and quantification. the selectivity, linearity, sensibility, detection, and quantification limits besides accuracy and precision parameters were studied and optimized under stabilized temperature platform furnace (stpf) conditions. the limit of detection obtained was 0.13 μg.l-1 and the limit of quantification was 1.04 μg.l-1, with an average precision, for total arsenic, less than 15% and an accuracy of 96%. to quantify the chemical species as(iii) and as(v), an ion-exchange resin (dowex 1x8, cl- form) was used and the physical-chemical parameters were optimized resulting in a recuperation of 98% of as(iii) and of 90% of as(v). the method was applied to groundwater, mineral water, and hemodialysis purified water samples. all results obtained were lower than the maximum limit values established by the legal brazilian regulations, in effect, 50, 10, and 5 μg.l-1 para as total, as(iii) e as(v), respectively. all results were statistically evaluated.
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