Determination of germanium by graphite-furnace atomic-absorption spectrometry

The premature loss of germanium as volatile GeO results in low sensitivity and poor reproducibility in the determination of germanium by graphite-furnace atomic-absorption spectrometry. This interference can be eliminated by suppressing the premature reduction of GeO(2) to GeO during the ashing step, and dissociating the germanium oxides into the atoms simultaneously with their vaporization during the atomization step. The premature reduction of GeO(2) to GeO has been successfully prevented by several approaches: (1) diminishing the reducing activity of the graphite furnace by (a) oxidizing the graphite surface and intercalating oxygen into the graphite lattice with oxidizing acids, such as nitric or perchloric, in the sample solution, or (b) using a tantalum-treated graphite furnace; (2) keeping the analyte as germanium (IV) by addition of sodium or potassium hydroxide to the sample solutions.     

Determination of gallium in geological materials by graphite-furnace atomic-absorption spectrometry

A graphite-furnace atomic-absorption spectrometric method has been worked out for the determination of traces of gallium in silicate rocks and minerals. The samples are opened up by fusion with a lithium carbonate-boric acid mixture and the cake is taken up with 2M nitric acid. Addition of nickel nitrate to this solution elminates the severe matrix effects allowing gallium solutions in nitric acid to be used as calibration standards. No separations are necessary. Results are quoted for 14 standard silicate rocks and two minerals. The RSD is 2.9%, and the sensitivity is 27 pg of gallium for 1% absorption.     

Determination of gallium in soil by slurry-sampling graphite-furnace atomic-absorption spectrometry

A graphite-furnace atomic-absorption spectrometric method, utilizing ultrasonic slurry-sampling has been developed for the determination of Ga in soils. Calibration with aqueous standards and with slurries prepared from a certified soil reference material were both employed. When calibration with soil slurries was used no modifier was needed. Because lower and more variable sensitivity was obtained for Ga in aqueous standards than for Ga in slurry soil samples, external calibration with aqueous Ga standards required a suitable chemical modifier to level out the sensitivity difference. Of the many potential modifiers tested, i.e. Al, As, Co, Mg, Mo, Ni, Pd, Pd+Mg, Se, and Te, Ni was found to be best. When Ni (1.0 mg mL(-1), 10 micro L) was injected to the graphite tube with the aqueous standards or slurry samples (10 micro L) accurate results were obtained. Both methods of calibration gave acceptable accuracy and precision. The repeatability was 相似文献   

Determination of yttrium and rare-earth elements in rocks by graphite-furnace atomic-absorption spectrometry

With use of synthetic solutions and several international standard reference materials a method has been developed for determining traces of Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in rocks by electrothermal atomization in a pyrolytically-coated graphite furnace. Depending on the element, the sensitivity is of the order of 10(-9)-10(-12) g at 2500 degrees . To avoid matrix interferences the lanthanides are separated from the common elements by co-precipitation with calcium and iron as carriers. The data for Canadian reference rock SY-2 (syenite), U.S.G.S. reference rocks W-2 (diabase), DNC-1 (diabase) and BIR-1 (basalt), and South African reference rock NIM-18/69 (carbonatite) obtained by graphite-furnace atomization are compared with the values obtained by flame atomic-absorption. The results are in good agreement with literature values.     

Determination of cadmium and lead in urine and other biological samples by graphite-furnace atomic-absorption spectrometry

A method for determining cadmium and lead in urine and other biological samples by graphite-furnace atomic-absorption spectrometry is reported. Samples were analysed after wet or dry ashing and without extraction or matrix-modification techniques, in laminar-flow clean-room; negligible blank contributions were found. Matrix interference effects were observed only for lead and were resolved by the method of standard additions. Five NBS biological reference materials were used as internal quality-control standards. The urinary levels for non-exposed volunteers ranged from 0.16 +/- 0.01 to 1.65 +/- 0.20 and from 6 +/- 1 to 31 +/- 6 ng/ml for cadmium and lead, respectively; this corresponds to 0.15 +/- 0.02 to 2.01 +/- 0.16 and 7 +/- 1 to 31 +/- 3 mug/day. The average relative standard deviation for 60 urine samples was 10% for cadmium and 13% for lead.     

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 °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. Received: 20 December 2000 / Revised: 3 April 2001 / Accepted: 5 April 2001     

Determination of total platinum in plasma and plasma ultrafiltrate,from subjects dosed with the platinum-containing N-(2-hydroxypropyl)methacrylamide copolymer AP5280, by use of graphite-furnace Zeeman atomic-absorption spectrometry

AP5280 is an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer to which are linked tetrapeptide side chains containing bioactive platinum complexes at their C-terminal sides. We have developed and validated a rapid and sensitive analytical assay for the determination of total platinum concentrations in plasma, and free platinum of an AP5280 origin in plasma ultrafiltrate (PUF), of subjects dosed with AP5280. The total platinum levels were determined by use of graphite-furnace atomic-absorption spectrometry (GF-AAS) with Zeeman correction after appropriate dilution of the plasma sample with plasma-hydrochloric acid 0.2 mol L(-1) (1:5) as diluent. The limit of quantitation of this assay is 0.25 micromol L(-1) platinum in plasma. Linear calibration curves were obtained over the concentration range 0.25-5.0 micromol L(-1). Accuracy was between 87.7% and 104.2% and precision was 15.3% at the lowest concentration and less than 14% for all other levels tested. Accuracy and precision were thus in accordance with generally accepted criteria for analytical methods. Analysis of samples obtained from patients receiving AP5280 demonstrated the applicability of the described assay.Analysis of free platinum in PUF was performed by use of a previously validated and reported assay from our institute in which the same instrumental method is used.     

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.     

Determination of traces of selenium in heat-resisting alloys by graphite-furnace atomic-absorption spectrometry after co-precipitation with arsenic

Traces of selenium in complex nickel- and cobalt-based heat-resisting alloys have been determined by co-precipitation and graphite-furnace atomic-absorption spectrometry. The alloys are dissolved in a mixture of concentrated hydrochloric acid, concentrated hydrofluoric acid and 30% hydrogen peroxide. Selenium does not volatilize to any significant extent during the dissolution and concentration. Selenium is separated from the matrices as the element by co-precipitation with arsenic and is redissolved in nitric acid. Zinc is added to the solution to stabilize selenium during the ashing step and thus to enhance the absorbance in the atomization step. Standard solutions for the calibration are prepared in a similar manner to sample solutions after dissolution of the arsenic carrier. The detection limit for selenium is 0.3 ppm in the heat-resisting alloy.     

Determination of thallium in cadmium and lead by graphite-furnace atomic-absorption spectrometry with sample vaporization from a platform

When the sample is vaporized from the wall of a graphite furnace it is not possible to determine thallium in cadmium and lead by AAS without matrix matching of the standards. In the case of a lead matrix and vaporization from the wall, the thallium signal is barely distinguishable from the base-line. When the sample is vaporized from a platform, and the peak area is used for measurement, pure aqueous standards may be used for instrument calibration. The peak heights and areas of the thallium signals are considerably enhanced by vaporization from a platform (peak height 1.7-fold and peak area 2.6-fold in pure aqueous solutions as compared to vaporization from the wall). The enhancement factors are larger in presence of the cadmium or lead matrix since here the reduced interference also makes a contribution.     

Determination of arsenic, cadmium, lead and selenium in highly mineralized waters by graphite-furnace atomic-absorption spectrometry

A graphite-furnace AAS method using the stabilized-temperature platform furnace (STPF) concept, mixed palladium and magnesium nitrates as chemical modifier and Zeeman background correction has been applied to the direct determination of As, Cd, Pb and Se in highly mineralized waters used for medicinal purposes. These contain 20-40 g/l. concentrations of salts, mainly sodium and magnesium chlorides, bicarbonates and sulphates. The use of a pre-atomization cool-down step to 20 degrees in the graphite-furnace programme reduced the background absorption. Increasing the mass of magnesium nitrate modifier to 5 times that originally proposed improved the analyte peak shape. Under these conditions, no interference was found in analysis of the chloride/bicarbonate type of water, but the sodium and magnesium sulphate type of water had to be diluted, and even then an interference remained. Calibration with matrix-free standard solutions was used, but use of spike recovery is strongly recommended for testing the accuracy. The limits of determination (4.65sigma) of the proposed method for undiluted samples are 2.0 mug/l. for As, 0.05 mug/l. for Cd, 1.0 mug/l. for Pb and 1.5 mug/l. for Se.     

Determination of tin and triorganotin compounds in sea-water by graphite-furnace atomic-absorption spectrophotometry

An analytical method based on graphite-furnace atomic-absorption spectrophotometry employing a suitable signal-enhancing medium for determination of inorganic tin and two of its trisubstituted organic derivatives in sea-water has been established. This method allows determination of triphenyltin and tributyltin compounds down to 2 x 10(-12) and 2.8 x 10(-12)M respectively by means of enrichment by collection on graphitized carbon black (enrichment factor up to 8 x 10(4)) and a separation on a small silica-gel column. Inorganic tin, which is not adsorbed on the graphitized carbon black, is isolated from the matrix by liquid-liquid extraction of its pyrrolidinedithiocarbamate complex into dichloromethane. The method gives good recovery (95%) and precision ( less, similar5%) at the ng/l. level.     

Determination of traces of tellurium in heat-resisting alloys by graphite-furnace atomic-absorption spectrometry after co-precipitation with arsenic

A simple analytical method has been developed for the determination of traces of Te in complex heat-resisting alloys by graphite-furnace atomic-absorption spectrometry. Nickel-base and cobalt-base heat-resisting alloys are dissolved in concentrated hydrochloric and hydrofluoric acids plus 30% hydrogen peroxide. Tellurium is separated from the matrix by co-precipitation with As and dissolved in nitric acid. Memory effects are eliminated by the oxidation of Te(IV) to Te(VI). Standard solutions for the calibration are prepared by the procedure used for the sample solution. The detection limit for Te is 0.05 ppm in the alloy.     

Determination of arsenic in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separation by xanthate extraction

A method for determining approximately 0.2 mug/g or more of arsenic in ores, concentrates and related materials is described. After sample decomposition arsenic(V) is reduced to arsenic(III) with titanium(III) and separated from iron, lead, zinc, copper, uranium, tin, antimony, bismuth and other elements by cyclohexane extraction of its xanthate complex from approximately 8-10M hydrochloric acid. After washing with 10M hydrochloric acid-2% thiourea solution to remove residual iron and co-extracted copper, followed by water to remove chloride, arsenic is stripped from the extract with 16M nitric acid and ultimately determined in a 2% nitric acid medium by graphite-furnace atomic-absorption spectrometry, at 193.7 nm, in the presence of thiourea (which eliminates interference from sulphate) and palladium as matrix modifiers. Small amounts of gold, platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, do not interfere.     

Preconcentration of nickel and cobalt on algae and determination by slurry graphite-furnace atomic-absorption spectrometry

Unicellular green algae have been utilized to preconcentrate Ni(2+) and Co(2+) ions from sea-water and riverine water samples. Studies have shown that rinsing the algae with 0.12M hydrochloric acid improves the adsorption of nickel and cobalt, and the optimum range of pH of extraction is wide. The maximum extraction efficiencies were 84 and 73% for Ni and Co, respectively, at ng/ml levels. The sea-water matrix and relatively small amounts of many impurities reduce the adsorption efficiency for both nickel and cobalt. The preconcentration is achieved by mixing 6 mg of algae with 50-100 ml of sample, and subsequently isolating the algae by centrifugation. The pellet of algae is then resuspended in 1 ml of 0.08M nitric acid, and analyzed as a slurry by graphite-furnace atomic-absorption spectrometry. The values found for nickel and cobalt in riverine (SLRS-1) and sea-water (CASS-1) standard reference materials are within the limits of certification.     

Determination of chromium in human milk and urine by graphite-furnace atomic absorption spectrometry

Low-temperature ashing and dry ashing at 500°C are compared for the analysis of urine and human milk. Dry ashing gives superior accuracy. The importance of contamination control, background correction and temperature control are stressed. Both urine and human milk contain about 1 ng Cr ml^-1.     

Structural aspects of the anti-cancer drug oxaliplatin: A combined theoretical and experimental study

The conformational behavior of the third generation antitumor drug, oxaliplatin, has been explored by GGA-PW91 density functional calculations and FT-IR spectra. The difference in the biological activities of cisplatin and oxaliplatin are attributed to the presence of the DACH ligand in the latter. The trans forms of the ligand are found to be more stable than the cis form, but, of the two equally stable enantiomers, the trans-l (1R,2R) one is found to be more potent biologically. Since very minor differences are observed in the electronic structures of the two enantiomers, their difference in activity is attributed to the chiral recognition of the ligand by DNA. The calculated vibrational frequencies are in good agreement with our experimental FT-IR spectrum. Calculations have also been performed on the cis isomer and its monohydrate. Comparison between the theoretically predicted geometries and the experimental ones yielded good correspondence, validating our methodology.     

Application of matrix-modification in determination of thallium in waste water by graphite-furnace atomic-absorption spectrometry

A method has been developed for the determination of thallium in waste water at the ng ml level by graphite-furnace atomic-absorption spectrometry. If microgram amounts of palladium or platinum are used as a matrix modifier, the ashing temperature for thallium can be raised to 1000 degrees , and the interference of halides and mineral acids is greatly reduced. The relative standard deviation found was 2% (9 replicate determinations) at the 8-ng ml thallium level, and the detection limit 1 ng ml .     

Determination of strontium in human tooth enamel by flameless atomic-absorption spectrometry

The determination of strontium in human tooth enamel by flameless atomic-absorption spectrometry was found to be subject to interference from the calcium/phosphate matrix of the enamel. The standard addition method was used to compensate for this interference. Hydrochloric acid and nitric acid did not affect the strontium absorption, but perchloric acid caused a significant reduction in the absorption. The sensitivity of the flameless atomic-absorption enabled 1-mg samples of enamel to be analysed. Hence, the proposed method can be used to determine the distribution of strontium through the tooth. An average recovery of 100.4% for amounts of strontium added to enamel showed that the proposed method was reliable.     

Determination of tellurium in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separations by iron collection and xanthate extraction

A method for determining approximately 0.01 mug/g or more of tellurium in ores, concentrates, rocks, soils and sediments is described. After sample decomposition and evaporation of the solution to incipient dryness, tellurium is separated from > 300 mug of copper by co-precipitation with hydrous ferric oxide from an ammoniacal medium and the precipitate is dissolved in 10M hydrochloric acid. Alternatively, for samples containing 300 mug of copper, the salts are dissolved in 10M hydrochloric acid. Tellurium in the resultant solutions is reduced to the quadrivalent state by heating and separated from iron, lead and various other elements by a single cyclohexane extraction of its xanthate complex from approximately 9.5M hydrochloric acid in the presence of thiosemicarbazide as a complexing agent for copper. After washing with 10M hydrochloric acid followed by water to remove residual iron, chloride and soluble salts, tellurium is stripped from the extract with 16M nitric acid and finally determined, in a 2% v/v nitric acid medium, by graphite-furnace atomic-absorption spectrometry at 214.3 nm in the presence of nickel as matrix modifier. Small amounts of gold and palladium, which are partly co-extracted as xanthates if the iron-collection step is omitted, do not interfere. Co-extraction of arsenic is avoided by volatilizing it as the bromide during the decomposition step. The method is directly applicable, without the co-precipitation step, to most rocks, soils and sediments.