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Hydrofluoric Acid (hydrofluoric + acid)
Selected AbstractsCorrosion of Ceramics in Aqueous Hydrofluoric AcidJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000Kurt R. Mikeska A variety of commercially available ceramic-based oxides, carbides, nitrides, and borides were evaluated for chemical attack in an azeotropic aqueous hydrofluoric acid (HF) test protocol at 90°C. Weight change measurements and microstructure analysis showed that HF corrosion in polycrystalline ceramics generally occurred at grain boundaries by the dissolution of grain boundary phases although the bulk single crystal may inherently resist attack. Virtually all commercially prepared polycrystalline oxide ceramics (i.e., Al2O3, TiO2, ZrO2) and nonoxide ceramics (i.e., Si3N4, AlN, BN) were extensively corroded while polycrystalline pure carbides (i.e., SiC, TiC, B4C, WC) resisted corrosion. Equilibrium thermodynamic calculations show that these materials are soluble in HF; however, the kinetics of dissolution are slow enough in some cases to permit useful engineering lifetimes. [source] Amiodarone Attenuates Fluoride-induced Hyperkalemia in VitroACADEMIC EMERGENCY MEDICINE, Issue 2 2003Mark Su MD Abstract Poisoning by hydrofluoric acid or fluoride salts results in hypocalcemia, hypomagnesemia, and hyperkalemia with subsequent cardiac dysrhythmias. In previous studies, quinidine attenuated fluoride-induced hyperkalemia in vitro, and enhanced survival in animals. Like quinidine, amiodarone is a potassium channel blocker, although amiodarone is more familiar to clinicians due to its recent inclusion in advanced cardiac life support (ACLS) protocols. Objectives: This in-vitro study of human erythrocytes was designed to determine whether amiodarone could attenuate fluoride-induced hyperkalemia. Methods: Six healthy volunteers each donated 60 mL of blood on three occasions. Each specimen was divided into 12 tubes, incubated at 37°C, and oxygenated with room air. An aqueous sodium fluoride (F,) solution was added to tubes 1,9. Incremental amounts of quinidine were added to tubes 1,4 (Q1,Q4) to attain calculated concentrations of 0.73 ,g/mL, 1.45 ,g/mL, 2.9 ,g/mL, and 5.8 ,g/mL, respectively. Incremental amounts of amiodarone were added to tubes 5,8 (A1,A4) to attain calculated concentrations of 0.38 ,g/mL, 0.75 ,g/mL, 1.5 ,g/mL, and 3.0 ,g/mL, respectively. Tubes 9,12 were controls for each of F,, amiodarone, quinidine alone, and no additive, respectively. Extracellular potassium concentration ([K+]) was followed, and an objective endpoint was defined as the rise in potassium concentration at 6 hours. Results: Fluoride produced a significant change in [K+] by 6 hours in all samples. Quinidine produced a J-shaped curve in its ability to attenuate the rise in [K+], with only one concentration, Q3, demonstrating significance versus tube 9 (control). Amiodarone also demonstrated a J-shaped dose,response effect, with statistical significance at A1, A2, and A3 versus tube 9 (control). There was no significant difference among the effective concentrations (Q3, A1, A2, and A3) of both drugs. Conclusions: In this in-vitro model using human blood, amiodarone and quinidine both attenuated F, -induced hyperkalemia. Further study is indicated to determine whether amiodarone enhances survival in F, -poisoned animals. [source] Surface characteristics of dentin experimentally exposed to hydrofluoric acidEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2003Thomas Pioch The purpose of this study was to test the effect of hydrofluoric acid (HF) on the surface characteristics of dentin in vitro. Dentin was exposed in 50 human molars and divided into five groups according to different etching schedules: (i) no etching, (ii) 15 s HF, (iii) 15 s H3PO4, (iv) 15 s HF and 15 s H3PO4, (v) 15 s H3PO4 and 15 s HF. Teeth were examined under a scanning electron microscope equipped with energy-dispersive X-ray (EDX) or two layers of fluorescence-labeled primer followed by the composite were applied, and the teeth were sectioned and examined using confocal laser scanning microscopy (CLSM). With scanning electron microscopy, no openings of dentinal tubules were found in groups (i), (ii), and (iv). In group (v) only a few tubules were opened and in group (iii) the smear layer was completely removed and tubules appeared open. The EDX analysis revealed that fluoride was incorporated into the dentin surface when HF was used. With CLSM, distinct hybrid layers could be detected only in group (iii). In group (v) the hybrid layer appeared less established compared with group (iii). No dentin hybridization was found in groups (i), (ii), and (iv). It is concluded that HF has the ability to close the openings of dentin tubules which were opened due to etching by phosphoric acid and cannot dissolve the smear layer. [source] Carbon and nitrogen isotope composition of bulk soils, particle-size fractions and organic material after treatment with hydrofluoric acidEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2005M. W. I. Schmidt Summary Soils and sediments contain only small amounts of organic matter, and large concentrations of paramagnetic metals can give poor solid-state nuclear magnetic resonance (NMR) spectra of organic matter. Pretreatment of samples with hydrofluoric acid (HF) dissolves significant proportions of the mineral matrix and extracts paramagnetic elements. We investigated the effects of 10% HF treatment on the stable isotope content of carbon (C) and nitrogen (N) of organic matter from soils, composts and shales. Additionally we inferred molecular and isotopic characteristics of lost materials from calculations of isotope mass balances. Treatment with HF enriched C and N in mineral samples substantially (factors 2.5,42.4), except for Podzol B horizons (1.1,1.7) and organic material (1.0,1.3). After treatment most of the C (59.7,91.7%) and N (53.7,86.6%) was recovered, although changing C/N ratios often indicated a preferential loss of N-rich material. Isotope ratios of C and N in the remaining material became more negative when net alterations exceeded 0.3,. The isotope ratios of the lost material contained more 13C (1,2,) and 15N (1,4,) than the initial organic matter. Acid hydrolysis typically removes proteins, amino acids and polysaccharides, all of which are enriched in 13C, and in the case of proteins and amino acids, enriched in 15N as well. We conclude that HF treatment released fresh, soluble, probably microbial, biomass in addition to carbohydrates. Net changes of the bulk chemical composition of organic matter were small for most soils, size fractions and plant material, but not for samples containing little organic matter, or those rich in easily soluble organic matter associated with iron oxides, such as Podzol B horizons. [source] Luminescent Colloidal Dispersion of Silicon Quantum Dots from Microwave Plasma Synthesis: Exploring the Photoluminescence Behavior Across the Visible SpectrumADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Anoop Gupta Abstract Aiming for a more practical route to highly stable visible photoluminescence (PL) from silicon, a novel approach to produce luminescent silicon nanoparticles (Si-NPs) is developed. Single crystalline Si-NPs are synthesized by pyrolysis of silane (SiH4) in a microwave plasma reactor at very high production rates (0.1,10,g,h,1). The emission wavelength of the Si-NPs is controlled by etching them in a mixture of hydrofluoric acid and nitric acid. Emission across the entire visible spectrum is obtained by varying the etching time. It is observed that the air oxidation of the etched Si-NPs profoundly affects their optical properties, and causes their emission to blue-shift and diminish in intensity with time. Modification of the silicon surface by UV-induced hydrosilylation also causes a shift in the spectrum. The nature of the shift (red/blue) is dependent on the emission wavelength of the etched Si-NPs. In addition, the amount of shift depends on the type of organic ligand on the silicon surface and the UV exposure time. The surface modification of Si-NPs with different alkenes results in highly stable PL and allows their dispersion in a variety of organic solvents. This method of producing macroscopic quantities of Si-NPs with very high PL stability opens new avenues to applications of silicon quantum dots in optoelectronic and biological fields, and paves the way towards their commercialization. [source] A Prospective Ten-Year Clinical Trial of Porcelain VeneersJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 2 2006Article first published online: 25 APR 200 abstract Objective:, The purpose of this prospective clinical study was to evaluate the performance of porcelain veneers after 5 and 10 years of clinical service. Materials and Methods:, A single experienced clinician placed 87 porcelain veneers in 25 patients in 1990 and 1991. The teeth included maxillary central incisors to first premolars. As described in the 5-year report of this study, preparations included a chamfer margin, 0.3 to 0.7 mm labial enamel reduction, and incisal edge coverage. A single laboratory technician fabricated the veneers using feldspathic porcelain on refractory dies. Internal surfaces were etched with 5% hydrofluoric acid and silanated. Teeth were isolated with a rubber dam prior to veneer placement. All veneers were bonded with a light-activated resin cement. Patients were recalled at 5 to 6 years and at 10 years after initial veneer placement. Two evaluators examined each veneer for retention, fractures, color match, surface roughness, marginal adaptation, leakage, recurrent caries, pulp vitality, and patient satisfaction. Marginal adaptation was assessed further using scanning electron microscopy to examine epoxy replicas. Results:, Five years after placement, all 87 veneers remained in place and had "perfect" color match and surface smoothness. Four veneers had fractures, but only one of those required repair. Ninety-nine percent of the veneers had clinically acceptable marginal adaptation, although just 14% of the veneers had "perfect" marginal adaptation at all margins. One had clinically unacceptable staining from leakage. Recurrent caries was present at the proximal margin of two veneers. At the 10-year evaluation, which had a 93% recall rate, color match and surface roughness remained optimal. Thirteen of 22 patients were very satisfied with the esthetic result, whereas 7 complained of minor esthetic problems. The fracture rate increased substantially, to 34% at the 10-year recall. However, only 11% of the fractures were clinically unacceptable. None of the veneers had debonded, but the percentage of veneers with "perfect" marginal adaptation had declined to only 4%. Leakage was now evident around two-thirds of the veneers, and eight restorations had recurrent caries. Conclusion:, Porcelain veneers are a reliable and effective means for conservative esthetic treatment of anterior teeth in the long term. After 10 years of clinical service, esthetic results remained good, patient satisfaction was high, and the retention rate was excellent. The number of irreparable fractures was low. Appropriate preparation design, occlusion, and use of adhesive materials contribute to the ultimate outcome. [source] Effect of different acid treatments on a porcelain surface1JOURNAL OF ORAL REHABILITATION, Issue 1 2001. Canay The objective of this study was to determine the effect of selected surface treatments on the surface texture of a feldspathic porcelain. The three different etchant treatments were, acidulated phosphate fluoride (APF) applied for 10 min and hydrofluoric acid (HF) applied for 1 and 4 min. After acid treatment, half of the specimens from each group were cleansed with water and others were subjected to ultrasonic cleaning and then dried. Half of the specimens cleansed with two different methods were treated with silane. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the effects of such treatments. Etching with APF displays shallow patterns. Etching for 1 min with HF displays deep channels, pores and precipitates on the surface and as the etching time increased these channels were replaced by larger channels. EDS analyses show that the crystalline precipitates on the etched surfaces, which were not readily soluble in water, were the reaction products of Na, K, Ca, Al, etc. HF displayed a more roughened surface than the APF gel. However, the precipitates remain on the surface after acid application, they can only be removed by ultrasonic cleaning and cannot be removed by rinsing. [source] Improved bonding of adhesive resin to sintered porcelain with the combination of acid etching and a two-liquid silane conditionerJOURNAL OF ORAL REHABILITATION, Issue 1 2001H. Kato This study determined the bond strengths of adhesive resins joined to a feldspathic porcelain (VMK 68) for the purpose of developing the most durable surface preparation for the porcelain. Three porcelain surfaces,ground, air-abraded with alumina, and etched with hydrofluoric acid,were prepared. A two-liquid porcelain conditioner that contained both 4-methacryloyloxyethyl trimellitate anhydride (4-META) and a silane coupler (Porcelain Liner M) was used as the priming agent. Each of the two liquid components of the conditioner was also used individually in order to examine the effects of the respective chemical ingredients on adhesive bonding. Two methyl methacrylate (MMA)-based resins initiated with tri- n -butylborane (TBB) either with or without 4-META (MMA-TBB and 4-META/MMA-TBB resins) were used as the luting agents. Shear bond strengths were determined both before and after thermocycling. Shear testing results indicated that thermocycling was effective for disclosing poor bonding systems, and that both mechanical and chemical retention were indispensable for bonding the porcelain. Of the combinations assessed, etching with hydrofluoric acid followed by two-liquid priming with the Porcelain Liner M material generated the most durable bond strength (33·3 MPa) for the porcelain bonded with the 4-META/MMA-TBB resin (Super-Bond C&B). [source] Effect of etching and sandblasting on bond strength to sintered porcelain of unfilled resinJOURNAL OF ORAL REHABILITATION, Issue 2 2000H. Kato This study determined the bond strength of an unfilled resin joined to a feldspathic porcelain for the purpose of evaluating the retentive performance of the prepared material surfaces. Porcelain disks (VMK 68 dentin) were either air abraded with alumina (AAA) or etched with one of the following five etchants: (1) ammonium hydrogen bifluoride (AHB); (2) acidulated phosphate fluoride (APF); (3) hydrofluoric acid (HFA); (4) phosphoric acid (PHA); and (5) sulfuric acid-hydrofluoric acid (SHF). Specimens ground with abrasive paper were also used as controls. After surface preparation, the two different sized porcelain disks were bonded together with a methyl methacrylate-based resin initiated with tri- n -butylborane (MMA-TBB resin). Shear bond strengths were determined both before and after thermocycling. Before the thermocycling, the greatest bond strengths (21·3 and 23·7 MPa) were generated with the use of the SHF and HFA agents, followed by the AHB agent (18·4 MPa). Reduction in bond strength after thermocycling was significant for all groups, although the SHF- and HFA-treated groups exhibited bond strengths greater than 15 MPa even after the thermocycling. The results indicated the effectiveness of the SHF- or HFA-etching for retaining the acrylic resin to the porcelain. However, ageing testing also revealed insufficient retentive characteristics of the acrylic resin by etching alone. [source] Comparison of Repair Methods for Ceramic-Fused-to-Metal CrownsJOURNAL OF PROSTHODONTICS, Issue 5 2006Mutlu Özcan DMD Purpose: The objective of this study was to evaluate the effect of four repair methods on the fracture load of repaired ceramic-fused-to-metal crowns. Materials and Methods: Metal-ceramic crowns were fractured, and the failure load was measured. The fractured metal-ceramic crowns (n = 9) were assigned randomly to the following treatment groups: (1) hydrofluoric acid (9.5%) etching, (2) air-particle abrasion (50 ,m Al2O3), (3) silica coating (30 ,m SiOx), and (4) the application of a layer of glass fiber-reinforced composite (FRC) (thickness: 0.12 mm) on the repair surface. The crowns were repaired with a highly filled resin composite and subjected to 3 repair cycles (n = 27). All specimens were stored in water at 37°C for 24 hours and then thermocycled (6000 cycles, 5°C to 55°C). The fracture load values for final failure of intact and repaired crowns were measured with a universal testing machine, and failure types were recorded. Results: No significant differences ( p > 0.05) were found between the final failure values for the groups treated with 9.5% hydrofluoric acid (376 N) and airborne particle abrasion with either Al2O3 (432 N) or SiOx (582 N) followed by silanization, respectively. Significantly, higher ( p < 0.0001) final failure values (885 N) were obtained with the use of the FRC layer when compared with the other repaired groups. There was no significant difference ( p > 0.05) between the final fracture load of intact crowns (872 N) and those repaired with FRC (885 N) (One-way ANOVA with repeated measures, Bonferroni test). No significant difference in fracture loads was found between the 1st, 2nd, and 3rd repair cycles (558 N, 433 N, 485 N, respectively). Failure sites were predominantly at the alloy/veneering resin interface in Group 1; Groups 2 and 3 both showed more cohesive failures than Group 1. In the case of FRC, the failure pattern was exclusively cohesive between the two laminates of FRC layer. Conclusions: The conditioning methods (Groups 1 to 3) of the repair surfaces did not show differences between each other; each resulted in mean fracture loads at lower levels than that of the intact crowns. Addition of an FRC layer increased the fracture load to the level of intact crowns. This suggests that the use of FRC in repairs of metal-ceramic crowns might be a viable option. [source] Optimization of a Nanoporous Silicon Layer for Solar Cell ApplicationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008Guk-Hwan An A pyramidal structure and an n/p junction-formed wafer were used for the porous silicon (PS) layer formation. The pyramidal structure was adopted to maximize the light confinement with the PS layer. Also, in order to apply the PS layer to the solar cell directly, the n/p junction was adopted. To optimize the PS layer on this new type of surface, three kinds of solutions, ethanol, N,N -dimethylformamide, and formamide (FA), were used with hydrofluoric acid as a base of electrolyte. Various current densities were applied for PS layer formation with various anodizing durations. The reflectance and the microstructure were used as criteria for the selection of the most suitable PS layer. Consequently, an effective reflectance of 2.4% was obtained with 50 mA/cm2 and 10 s under the FA-based electrolyte condition. The result was expected to be used as an antireflection coating for solar cell applications. [source] Corrosion of Ceramics in Aqueous Hydrofluoric AcidJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000Kurt R. Mikeska A variety of commercially available ceramic-based oxides, carbides, nitrides, and borides were evaluated for chemical attack in an azeotropic aqueous hydrofluoric acid (HF) test protocol at 90°C. Weight change measurements and microstructure analysis showed that HF corrosion in polycrystalline ceramics generally occurred at grain boundaries by the dissolution of grain boundary phases although the bulk single crystal may inherently resist attack. Virtually all commercially prepared polycrystalline oxide ceramics (i.e., Al2O3, TiO2, ZrO2) and nonoxide ceramics (i.e., Si3N4, AlN, BN) were extensively corroded while polycrystalline pure carbides (i.e., SiC, TiC, B4C, WC) resisted corrosion. Equilibrium thermodynamic calculations show that these materials are soluble in HF; however, the kinetics of dissolution are slow enough in some cases to permit useful engineering lifetimes. [source] Molecular Characteristics of Poly(N -isopropylacrylamide) Separated from Nanocomposite Gels by Removal of Clay from the Polymer/Clay NetworkMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2010Kazutoshi Haraguchi Abstract The extraordinary mechanical and swelling/deswelling properties of nanocomposite (NC) gels are attributed to their unique organic (polymer)/inorganic (clay) network structure. In this study, poly(N -isopropylacrylamide) (PNIPA) was successfully separated from an NC gel network by decomposing the clay (hectorite) using hydrofluoric acid (HF). A very low HF concentration (0.2,wt.-%) was adequate for the decomposition of the clay without causing any damage to PNIPA. The separated PNIPA had a high (=5.5,×,106 g,·,mol,1). Also, was almost constant regardless of the clay concentration (Cclay,=,1,25,×,10,2 mol,·,l,1), even though the properties of the NC gel varied widely over this Cclay range. Comparisons of NC gels, PNIPA, and SiO2 -NC gels indicated that the clay platelets specifically play an important role in NC gels. [source] Preparation of Stable Colloidal Crystals and Macroporous Materials Using Diazoresin as a Thermosetting AgentMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2004Hailin Cong Abstract Summary: Two kinds of stable colloidal crystals have been prepared from polymeric or SiO2 colloids in the presence of diazoresin (DR) as a thermosetting agent combining thermal treatment. Following the decomposition of N groups of DR under heating, the ionic bonds between the DR molecules and colloids change to covalent bonds and the colloidal crystals become very stable toward ultrasonic washing. The colloids were then removed by tetrahydrofuran (THF) in the case of organics or by hydrofluoric acid (HF) for the inorganics to leave the macroporous DR materials. Reactions between the DR molecules and the colloids during thermal treatment. [source] Liquid level sensor using etched silica fiberMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010J. Linesh Abstract An all optical fiber, intensity modulated sensor for discrete liquid level sensing is presented. The highly sensitive and robust design requires only silica fibers, an optical source and a detector. The sensor probe is prepared by etching the silica fibers using hydrofluoric acid. Experiments conducted with water confirm the ability of the sensor to detect liquid level variation below 10 ,m. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:883,886, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25037 [source] Cross-sectional AFM study of etching kinetics of oxidized porous siliconPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004J. C. Poler Abstract We have studied the morphology and etching kinetics of partially oxidized porous silicon films. Film morphology and thickness was measured using cross-sectional atomic force microscopy. Air and UV-ozone oxidized porous silicon films were etched in buffered hydrofluoric acid. The observed etching rate was much faster than expected for a bulk film. These data consist of: direct visualization of cluster formation, enhanced etching rates and subsequent analysis of the liberated nanoparticles, and consistent with a mesoporous morphology of undulating Si nanowires. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Products of the interaction of (1-diaminomethylene)thiourea with hydrofluoric acidACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009gorzata Ho The salts 1-(diaminomethylene)thiouron-1-ium hydrogen difluoride, C2H7N4S+·HF2,, (I), and bis[1-(diaminomethylene)thiouron-1-ium] hexafluoridosilicate, 2C2H7N4S+·SiF62,, (II), have both been obtained from the reaction of (1-diaminomethylene)thiourea (HATU) with hydrofluoric acid. Both compounds contain extensive networks of N,H...F hydrogen bonds. The hydrogen difluoride salt contains four independent asymmetric [HF2], anions. In the hexafluoridosilicate salt, the centrosymmetric [SiF6]2, anion is distorted, although this distortion is not clearly correlated with the N,H...F hydrogen-bonding network. [source] Chemical injuries: The Tasmanian burns unit experienceANZ JOURNAL OF SURGERY, Issue 1-2 2003Sophie Ricketts Background: Chemical burns account for relatively few admissions to a burns unit. These injuries, however, deserve separate consideration because of their ability to cause continuing tissue destruction, their potential to cause systemic toxicity and the value of early treatment with copious lavage. Widespread inexperience in the treatment of chemical burns highlights the potential for greater levels of general awareness and knowledge. Methods: A review of 31 patients with chemical injuries admitted to the Tasmanian Burns Unit at the Royal Hobart Hospital (RHH) was carried out for the years 1989,1999. Results: The majority of patients were men aged 20,49 years (mean age: 32 years). Fifty-one per cent of injuries occurred in a domestic and 38% in an industrial setting. The more common aetiological agents were cement (25%), sulphuric acid (16%) and hydrofluoric acid (16%). The upper and lower extremities were involved in all but four patients and the mean total body surface area affected was 3.4%. The mean length of hospital stay was 9 days with a range of 1,30 days. Management of injuries consisted of either surgical or conservative treatment. The former included debridement and split-thickness skin grafting or primary closure and the latter of topical treatment with 1% silver sulfadiazine cream and appropriate dressings. Conclusion: Widespread inexperience in the treatment of chemical injuries highlights the potential for greater levels of knowledge. This is particularly apparent in the early management of these injuries. [source] PROVENANCE OF ANCIENT TEXTILES,A PILOT STUDY EVALUATING THE STRONTIUM ISOTOPE SYSTEM IN WOOL*ARCHAEOMETRY, Issue 2 2009K. M. FREI Strontium isotopes are used in archaeology to reconstruct human and animal migration routes. We present results of a pilot study applying strontium isotope analyses to modern sheep hair as a basis for its potential use as a provenance tracer for ancient woollen textiles. Our hydrofluoric acid-based, lipid soluble analytical protocol, also tested on a number of ancient textile fibres, allows for contamination-free, low blank strontium isotope analysis of minimal amounts of archaeological material. 87Sr/86Sr ratios of decontaminated sheep hair agree well with the compositions of biologically available (soluble) strontium fractions from the respective feeding ground soils, a translatable requirement for any potentially successful provenance tracing applied to wool textiles. [source] Determination of Selenium Concentration in Sixty Five Reference Materials for Geochemical Analysis by GFAAS after Separation with Thiol CottonGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001Luc Marin sélénium; SAA four graphite; séparation; matériaux géologiques de référence; coton thiol Selenium has been determined in sixty five geological reference materials of different origins by graphite furnace atomic absorption spectrometry. Samples were decomposed with a mixture of nitric and hydrofluoric acids. Selenium was reduced to SeIV with hydrochloric acid, and then fixed and separated from the matrix on thiol cotton. After digestion of the thiol cotton in hot nitric acid, the Se concentration was measured using palladium and magnesium nitrates as a matrix modifier. The limit of determination was 0.02 ,g g,1, the precision of the results (relative standard deviation of 3 to 8 replicates) varied from 2.6 to 17.7% with an average of 7.9% in the range 0.02-42.7 ,g g,1 and was similar to the value obtained for synthetic samples. Our results are in good agreement with available literature values. Le sélénium a été dosé sur 65 standards géochimiques de référence de différentes provenances par spectrométrie d'absorption atomique avec four graphite. Les échantillons ont été mis en solution par une attaque acide HNO3 -HF. Le sélénium a été réduit en SeIV avec de l'acide chlorhydrique, fixé et séparé de la matrice sur du coton thiol. Après décomposition du coton thiol par chauffage avec de l'acide nitrique, les concentrations en sélénium ont été mesurées en utilisant du nitrate de palladium et de magnésium comme modificateur de matrice. La limite de détermination est de 0.02 ,g g,1, la précision des résultats (écart type relatif sur 3 à 8 mesures) pour les standards géochimiques varie de 2.6 à 17.7% avec une moyenne de 7.9% dans la game 0.02-42.7 ,g g,1et est comparable à celle obtenue pour des échantillons synthétiques. Nos résultats sont en bonne concordance avec les résultats déjà publiés dans la littérature. [source] | |||||||||||||||||||