PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Graphite”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2006

Direct determination of nickel in petroleum by solid sampling-graphite furnace atomic absorption spectrometry.

A procedure for the direct GFAAS determination of Ni in petroleum samples using a solid sampling strategy is proposed. Palladium was used as conventional modifier. Central composite design multivariate optimization defined the optimum temperature program and the Pd mass, allowing calibration using aqueous analytical solution. The limit of detection (LOD) at the optimized conditions was 0.23 ng of Ni, for typical sample masses between of 0.10 and 0.60 mg. Linearity at least up to 11 ng of Ni and a characteristic mass of 45 pg were observed, defining a dynamic range between 0.52 and 110 microg g(-1). Typical coefficients of variation (n = 10) in the analysis of oil reference materials were 7%. Method validation was performed both by the analysis of oil certified reference materials and by comparison with an independent method (ASTM 5863-B). No statistically significant difference was observed between obtained and expected values. The total determination cycle lasted 5 min, equivalent to a sample throughput of 6 h(-1) for duplicate determinations.

Journal Article↗
PubMed2000

Effects of various salts on the determination of arsenic by graphite furnace atomic absorption spectrometry. Direct determination in seawater.

The effect of Na, Mg, Ca and Sr as their nitrate, chloride and sulfate salts and seasalt, with and without the use of palladium, on the determination of arsenic by electrothermal atomic absorption spectrometry was investigated. In the absence of any stabilizing agent, arsenic was partially lost as molecular species at low temperatures. The effect of salts on the shape of the atomization signal, the integrated absorbance and the stabilizing effect were highly dependent both on their nature and mass. By trapping arsenic, oxide species resulting from the decomposition of nitrate salts induced a high stabilization effect depending on their vaporization temperatures: MgO approximately CaO>SrO>Na2O. The stabilization effect of chlorides occurred about 200 degrees C lower and depended on mass, volatility and hydrolytic properties: SrCl2>CaCl2>MgCl2 approximately NaCl. The effect of sulfates was mainly dependent on their decomposition/vaporization mechanisms, and in the presence of Na2SO4 or CaSO4 a strong chemical interference effect was observed. Palladium stabilized arsenic in the presence of nitrates, chlorides or even sulfates, leading to a similar delaying effect, signal shape and integrated absorbance. Seasalt induced also important modifications to the atomization signal of As. Moreover, an interference effect was observed, which could probably be attributed to the simultaneous vaporization of sulfate in seasalt. In seawater, Pd suppressed this interference effect and permitted to use a high pyrolysis temperature up to 1400 C to remove the major part of the seawater matrix before atomization. Under optimized conditions, the detection limit for As obtained in unmodified seawater in the presence of Pd was 0.34 microg L(-1) for a 10 microl sample.

Journal Article↗
PubMed2000

Determination of soluble and insoluble nickel compounds in airborne particulate matter by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry.

An extraction procedure for the determination of soluble and insoluble nickel and its compounds in ambient air dust was investigated employing a special device for the generation of test aerosols and using water-soluble NiCl2, partly water-soluble NiCO3 and water-insoluble NiO as model compounds. Additionally, results of the separation and determination of different nickel species down to some ng/m3 in ambient aerosols are discussed. The extraction was carried out with a solution containing 0.01 mol/L EDTA in order to determine partly water-soluble compounds such as NiCO3 and water-soluble, non-toxic nickel compounds in one step. Airborne dust was sampled on filters at locations close to two metallurgical plants in Northrhine-Westphalia (Germany), and first results on the nickel concentration (mean (median) values over a period of 4 months: 8.6+/-6.5 ng/m3 (6.7 ng/m3) and 27.7+/-36 ng/m3 (10.8 ng/m3), respectively) in the collected dust are presented. For EDTA-soluble nickel compounds the maximum and mean fractions of total nickel were found to be 77.1% and 18.6+/-12%, respectively.

Aerosols↗
PubMed2000

Validated method for the determination of platinum from a liposomal source (SPI-77) in human plasma using graphite furnace Zeeman atomic absorption spectrometry.

A sensitive analytical method based on flameless atomic absorption spectrometry with Zeeman correction has been validated for the quantitative determination in human plasma of platinum originating from cisplatin in a liposomal source, SPI-77. The performance of the method was acceptable over a sample concentration range of 0. 125-1.25 micromol platinum/L and the lower limit of quantification was determined to be 1.25 micromol platinum/L in undiluted clinical samples. The performance data of the assay were investigated using both a calibration curve with carboplatin in plasma ultrafiltrate and diluted human plasma samples spiked with SPI-77. The recoveries, between-day and the within-day precisions of both methods of calibration were not significantly different allowing carboplatin ultrafiltrate calibration standards to be used to quantify platinum derived from SPI-77 in human plasma. Apparently, the liposomal formulation had no significant influence on the determination of platinum. The usefulness of the presented method was demonstrated in a phase I clinical and pharmacokinetic study. In addition, in vitro experiments were carried out to determine the distribution of SPI-77 in blood. The results indicated that platinum from SPI-77 mainly concentrates in plasma and that binding to and/or endocytosis in red blood cells is negligible.

Antineoplastic Agents↗
PubMed2001

Determination of selenium in soils by slurry-sampling graphite-furnace atomic-absorption spectrometry with polytetrafluoroethylene as silica modifier.

A 6% slurry of polytetrafluoroethylene (PTFE) in 4% hydrofluoric acid and 1% nickel nitrate were used as modifiers for determination of selenium in soils by GF AAS. PTFE was used to remove silica from the soil sample, because this resulted in severe matrix effects. The temperature of fluorination, determined thermogravimetrically, was 600 degrees C. The yield of fluorination depends on the molar ratio of PTFE/silica, particle size, and the time and temperature of fluorination. The soil samples were pretreated with a small amount of concentrated hydrofluoric acid placed directly in the cup of autosampler. The results for the determination of selenium in the reference soil materials by means of the slurry-sampling technique and use of aqueous standards are in good agreement with the certified values.

Polytetrafluoroethylene↗
PubMed2001

The determination of low lead levels in the bone of lead-depleted mice by graphite furnace atomic absorption spectrometry.

Low lead levels in the femurs of mice fed with a lead-depleted diet have been determined by use of electrothermal atomic absorption spectrometry with Zeeman-effect background correction. The method is based on the use of Mg(NO3)2/Pd as matrix modifier which enables significant reduction of the spectral interferences prevalent if chemical modifiers based on NH4H2PO4 with either Ca or Mg are used for samples rich in Ca3(PO4)2 matrix. The method was developed and validated by use of the NIST standard reference material 1486 bone. Bones were decomposed in a pressurized microwave-heated system using 70% nitric acid. Forty-three mice femurs, with a mass of 74.62 +/- 12.54 mg, were dissolved in concentrated nitric acid. The lead results found in SRM 1486 (1.25 +/- 0.15 microg g(-1), n = 9) were in good agreement with the certificate (1.335 +/- 0.014 microg g(-1)). Recoveries of 200 ng lead added to the SRM before or after digestion were 99.0 +/- 1.4% and 98.5 +/- 1.6%, respectively. The lead detection limit in bone samples is 0.06 microg g(-1) dry mass. This method is, therefore, suitable for the determination of very low lead levels (0.06-0.20 microg Pb kg(-1) bone) in the femurs of mice fed a diet with lead level of < 20 microg kg(-1).

Animals↗
PubMed1979

[Microdetermination of lead and cadmium in blood and urine by graphite furnace atomic absorption spectrophotometry (author's transl)].

A microtechnique is described for determination of lead and cadmium in blood (0.1 ml) and in urine (0.2 ml) using extraction into methyl isobutyl-ketone after chelation by ammonium pyrrolidine dithiocarbamate. Mineralization, precipitation of proteins or addition of hemolysing reagents are not necessary. Blood is hemolysed by addition of deionised water. pH of urine is fixed by a pH 5 buffer. This microtechnique is simple, rapid, reproducible and suitable for routine analysis. In healthy subjects it gives values comparable to data of other workers: blood 158 microgram/l lead (s = 40, n = 18); 0.7 microgram/l cadmium (s = 0.3, n = 10); urine 16 microgram/l lead (s = 9.4, n = 10); 0.5 microgram/l cadmium (s = 0.3, n = 10).

Cadmium↗
PubMed1991

Effectiveness of palladium matrix modification for the determination of thallium by graphite furnace atomic absorption spectrometry.

The effect of palladium matrix modification on the determination of thallium has been investigated. The effect of palladium combined either with ammonium nitrate or with magnesium nitrate on the sodium chloride interference was systematically studied and was compared with that of the classical sulfuric acid modifier. A combination of 6 micrograms palladium with 100 micrograms ammonium nitrate allows the direct determination of thallium in ten-fold diluted blood against matrix-free standards. The detection limit (3 sigma) in the undiluted blood was calculated to be 25 micrograms.1(-1). For the urine analysis the standard addition technique is recommended because a complete thallium recovery for all different urine samples studied was not always obtained.

Hot Temperature↗
PubMed1992

Comparison of wet digestion procedures for the determination of cadmium and lead in marine biological tissues by Zeeman graphite furnace atomic absorption spectrophotometry.

Three wet digestion procedures, namely, nitric acid/sulphuric acid, nitric acid/hydrogen peroxide and nitric acid/perchloric acid were compared for their relative efficiency in determining cadmium and lead in marine biological tissues. The nitric acid/perchloric acid procedure was the most efficient, whereas the nitric acid/hydrogen peroxide procedure was the least efficient. The nitric acid/sulphuric acid procedure was also found to be effective but there was a problem with the method as the presence of sulphuric acid in the matrix markedly suppressed the absorbance signals especially for lead analysis and thus reduced sensitivity. The addition of ascorbic acid as matrix modifier improved sensitivity. However, this analysis still required the standard addition method. No apparent interferences were encountered for cadmium analysis.

Animals↗
PubMed2005

A solid phase extraction procedure for indium prior to its graphite furnace atomic absorption spectrometric determination.

A procedure based on solid phase extraction of indium ions at trace level on Chromosorb 108 resin as bathocuproinedisulfonic acid chelate is presented for its preconcentration. The optimum pH value for quantitative sorption is 8.0-9.0, and desorption can be achieved by using 10.0 ml of 2 M HNO3. The effects of diverse ions on the sorption and recovery of indium have been studied. The capacity of sorbent was 3.78 mg In/g resin. Recoveries for indium from water samples were in the range 95-105%. The accuracy of procedure was confirmed by indium determination in certified reference materials. The method developed was applied with varying results to the analysis of real samples including metallic zinc with satisfactory results.

Indium↗