Arsine Research Articles

The effect of arsenicals on ultraviolet-radiation-induced growth arrest and related signaling events in human keratinocytes.

The molecular mechanisms mediating arsenic-induced carcinogenesis are not well understood. The role of confounding factors such as ultraviolet radiation (UV), add another level of complexity to the study of arsenic carcinogenesis and the cancer-risk assessment on humans. We hypothesized that arsenicals are capable of overriding the growth arrest caused by UV treatment and may lead to selective proliferation. To test this hypothesis, a primary normal human epidermal keratinocyte (NHEK) cell culture model was used. One group was pre-exposed to UVB (100 mJ/cm(2)) that arrested a majority ( approximately 95%) of cells in G0/G1 (+UV) and a second group was not exposed to UV (-UV). Treatment of cells with various arsenicals [0-12 microM of inorganic arsenite (iAs), 0-2 microM of methyl oxoarsine (MMAs III) and 0-3 microM of iododimethyl arsine (DMAs III)] indicated a concentration-dependent increase in proliferation at 24 h in the order of DMAs III > MMAs III > iAs. Flow-cytometric analyses revealed differential effects on cell cycle distribution. Analysis of a battery of cell cycle proteins (cyclin D1, cdk5, PCNA, cdc25A and cdc25C) indicated exposure-specific differential expression profiles. Increased activation of JNK phosphorylation (5-10-fold) in the +UV group and the synergistic increase with methyl arsenicals suggested that JNK might be involved in cell survival and proliferative signaling. Induction of EGF levels and increased phosphorylation of the EGF receptor by arsenicals (+UV) suggested that the EGF signaling pathway might mediate arsenical-induced cell proliferation of NHEK cells. Differential activation of ERK1/2 by arsenicals (+/-UV) suggested that EGF-mediated cell proliferation by arsenicals in UV-treated NHEK cells may not involve ERK activation. Taken together, the data suggest that both UV exposure and methylation status of the arsenicals dictate the participation of key cell cycle proteins and related signaling events in arsenical-induced cell proliferation.

Direct analysis of natural waters for arsenic species by hydride generation atomic absorption spectrometry

Selective reaction media were applied to generate hydrides of total arsenic, As(III), As(V), dimethylarsonic acid (DMA) and monomethylarsonic acid (MMA) from natural waters acidified with HCl (0.1 mol/L HCl in the sample) using reduction with 0.6% NaBH4 in a continuous flow hydride generation system: 1. 1.0 mol/L HCl in the acid channel, water samples pretreated with KI: determination of As(III) + As(V) + MMA 2. 6.0 mol/L CH3COOH in the acid channel: determination of As(III) + DMA 3. 6.0 mol/L CH3COOH in the acid channel, water samples pretreated with KI: determination of As(III) + As(V) + DMA 4. 1.0 M tartaric acid in the acid channel, water samples pretreated with KI: determination of total arsenic As(III) + As(V) + DMA + MMA With the selected medium reactions (1–4) the same response can be obtained for all arsenic species. Calibration with arsenic(III) standard solutions was applicable to the four reactions for arsenic speciation in mineral water, underground water and sea water.

1.24 μ m InGaAs/GaAs quantum dot laser grown by metalorganic chemical vapor deposition using tertiarybutylarsine

Metalorganic chemical vapor deposition of GaAs-based laser diodes, using self-organized InGaAs quantum dots (QDs), emitting at >1.24 μm is demonstrated. The environment-friendly alternative precursor tertiarybutylarsine is used as a substitute for arsenic hydride. The active region contains ten closely stacked InGaAs QD layers embedded in a GaAs matrix. Lasing emission at such long wavelengths was achieved by overgrowing the In0.65Ga0.35As QDs with a thin In0.2Ga0.8As film. The application of an in situ annealing step leading to the evaporation of plastically relaxed defect clusters is shown to be decisive for the laser performance. A transparency current density of 7.2 A/cm2 per QD layer and an internal quantum efficiency of 75% were achieved at room temperature.

Trapping of hydride forming elements within miniature electrothermal devices: part I. investigation of collection of arsenic and selenium hydrides on a molybdenum foil strip

The interaction of selenium and arsenic hydrides with surface of bare and modified (Pt, Ir and Rh) strips of the molybdenum foil was investigated by atomic absorption spectrometry employing miniature hydrogen diffusion flame as a simple atomizer and by radiotracer technique using 75Se-radionuclide as an indicator. In contrast to the recently reported data for tungsten atomizers, enhanced trapping was observed at the temperatures above 1000 °C, close to 1100–1200 °C, for the bare and modified molybdenum foil strips, irrespective of the analyte, and amount and type of the modifier deposited. When using a 75Se-radiotracer, the same selenium trapping efficiency of approximately 30% was found for the bare and rhodium-treated foils at the temperature of 1200 °C. Trapping isotherms of both analytes appeared to be very close to the linear fit even up to the upper limit of the analytical relevancy of 100 ng of an analyte, indicating a very high trapping capacity of the bare and modified surfaces. The influence of injection gas flow rate and capillary distance suggested that aerodynamic conditions of the injected gas near the molybdenum surface play significant role in trapping both analytes. The maximum trapping efficiency was reached for flow rates close to 60–70 ml min −1 and for a relatively short distance of 1–2 mm between the capillary orifice and the foil surface. Radiography experiments with 75Se-radiotracer showed that a major part of selenium was collected on a relatively small area, in the central part of the strip, opposite the orifice of the injection capillary. After trapping and vaporization steps, deposits of the selenium tracer were also found on the quartz tube wall of the trap chamber, close to the heated part of the strip.

Germanium Phosphines, Arsines, and Stibines

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hydride generation from slurry samples after ultrasonication and ozonation for the direct determination of trace amounts of As(iii) and total inorganic arsenic by their in situ trapping followed by graphite furnace atomic absorption spectrometry

A slurry sampling hydride generation method for As(III) and total inorganic As, without total sample digestion, has been developed using a continuous flow mode generation system coupled with atomic absorption spectrometric determination from environmental (marine sediment, soil, rock salt, waste water) and biological (human hair and urine, lobster, liver, muscle, beer and wort, tablets) samples. It involves trapping of the arsenic vapor on a pre-heated graphite furnace inner wall at 300 °C, treated with 150 µg of iridium as chemical permanent modifier, and determination by graphite furnace atomic absorption spectrometry (GF-AAS). The same graphite tube could be used for at least 200 cycles without any re-treatment. It was shown that this relatively simple and nearly direct procedure could give total arsenic concentrations very close to those obtained by analytical procedures requiring total sample decomposition and dissolution of organic and inorganic matter prior to the determination of analyte. Pretreatment of samples (slurried in HCl with addition of ozone) by ultrasonic agitation enabled the extraction of more than a 95% confidence level of the total arsenic from the certificate or close to the information value of the reference materials investigated. For the estimation of As(III) and As(V) concentrations in samples, the difference between the analytical sensitivities of the absorbance signals obtained for arsenic hydride without and with previous treatment of samples with thiourea can be used. The concentration of arsenate (As(V)) was calculated by the difference between total As and As(III). Reference and real sample materials were analyzed. The accuracy of the developed slurry sampling hydride generation method has been verified by analyzing several certified reference materials (TORT-1, DOLT-2, LUTS-1, DORM-1, BCSS-1, GBW 07601, NIST SRM 2709, LKSD-2, NIES CRM No. 18). The good agreement with the certified value confirms the validity of such a method for As determination instead of wet digestion procedures. The advantage of the method was that only a minimum of reagents and sample handling were required, reducing the risks of contamination and/or analyte loss and that non-chromatographic speciation approaches have been developed. However, the calibration was achieved via the technique of standard additions. In optimized conditions by Simplex the method shows an absolute detection limit (3σblank) of 1.5 ng, obtained with a 60 s trapping time using NaBH4 as reductant with Ir modifier, which corresponds to an LOD (10σ) of 4.8 ng g−1 As in sample. The relative standard deviation (RSD) of 7.8% was obtained for As concentration at the level of 20 ng g−1. The overall efficiency of the volatile species generation and trapping process estimated for arsenic was 89%. A particle size less than 20 µm is adequate to obtain total vapor generation of As content in the acidic slurry particles.

Flow analysis-hydride generation-Fourier transform infrared spectrometry. A new analytical technique for the simultaneous determination of antimony, arsenic and tin.

The combination of flow analysis (FA), hydride generation (HG) and Fourier transform infrared (FTIR) spectrometry is proposed as a novel and powerful analytical technique for the individual and simultaneous determination of antimony, arsenic and tin in aqueous samples. The analytes were transformed into the volatile hydride form by on-line reaction with sodium tetrahydroborate in acidic medium. The gaseous analyte hydrides [M(n)H(m), (g)] generated, were transported by means of a carrier gas stream inside the IR gas cell and the corresponding FTIR spectrum was acquired in a continuous mode. The 1893, 1904 and 2115 cm(-1) bands of the SbH3, SnH4, and AsH3 were selected for the determination of antimony, tin and arsenic, respectively. The limit of detection (3sigma) obtained by using a short-path (10 cm) IR gas cell were 0.25, 0.30 and 1.2 mg l(-1) for the determination of antimony, tin and arsenic, respectively; while the precision (relative standard deviation, RSD, n 5) found from a standard solution containing 50 mg l(-1) of each element was, in all cases, less than 0.3%. However, the use of a long-path (7.25 m) IR gas cell improved the figures of merit (sensitivity, limits of detection and quantification) nearly 60-fold. The effect of the main experimental and instrumental variables, such as acidic media, sodium tetraborohydrate concentration, nitrogen flow rate, nominal resolution and the scan accumulation on the analytical signals of the antimony, tin and arsenic hydrides, were studied. Further, the potential of the proposed technique for the simultaneous determination of these elements was tested, analyzing synthetic samples containing different amounts of Sb, Sn and As.

Derivatization of organometal(loid) species by sodium borohydride: Problems and solutions

Like other derivatization techniques, hydride generation is a chemical reaction that produces side-reactions leading to analytical problems. Demethylation of dimethylarsinic acid was observed to be dependent upon the pH level of the hydride generation reaction mixture. If the reaction mixture was acidic, then in addition to (CH 3) 2AsH, the monomethyl arsenic hydride [(CH 3)AsH 2] could be detected. Demethylation and also the formation of an unidentified arsenic species were noted when trimethyl arsonic oxide was used as derivatization educt. All of these effects depend on the pH level of the hydride generation mixture. We observed significant levels of organometal(loid) species of elements such as Ge, As, Sn, Sb, Hg and Bi in blank hydride generation mixtures. The organometal(loid) contamination was irreproducible even during 1 day using a single solution of sodium borohydride in deionized water. We concluded that the organometal(loid) contamination arises directly from the derivatization agent, sodium borohydride, itself. Use of helium purging and various adsorptive materials to decontaminate the sodium borohydride solution prior to analysis did not result in a significant decrease in organometal(loid) contamination levels. Use of a palladium-cluster stabilised with 1,10-phenanthrolin as alternative hydride generation derivatization agent was not found to be suitable, since reaction yields were poor and transmethylation reactions were noted.

Multivariate optimisation of hydride generation procedures for single element determinations of As, Cd, Sb and Se in natural waters by electrothermal atomic absorption spectrometry

Continuous flow hydride generation procedures for As(III), total inorganic As, Cd, total inorganic Sb, Se(IV) and total inorganic Se from sea and hot-spring water samples were optimised by experimental designs. Ir-coated graphite tubes were used as preconcentration and atomisation medium of the hydrides generated. Several factors affecting the hydride generation efficiency were studied. Results obtained from Plackett–Burman designs suggest that sodium borohydride flow rate and reduction coil length, are significant factors for total inorganic arsenic hydride generation. For cadmium hydride generation the significant factors are hydrochloric acid concentration, hydrochloric acid and sodium borohydride flow rates and reduction coil length. For total inorganic antimony hydride generation the factors affecting the hydride generation procedure are hydrochloric acid and potassium iodide concentrations and reduction coil length; finally, pre-reduction coil length and oven temperature for the pre-reduction step are statistically significant factors for total inorganic selenium hydride generation. In addition, the factors studied for the arsenic and selenium hydride generation from As(III) and Se(IV) are not significant. From these studies, the significant variables were optimised by central composite designs. Validation carried out analysis on three reference materials: SLRS-4 (Riverie water), CASS-3 (seawater) and NIST-1643d.

Investigation of in situ trapping of selenium and arsenic hydrides within a tungsten tube atomiser

The capability of in situ trapping of selenium and arsenic hydrides within a bare and modified (Pd, Pt, Ir and Re ) tungsten tube atomiser (WETA) was investigated by electrothermal atomic absorption spectrometry and by a radiotracer technique using 75Se radionuclide. Low efficiency of trapping (below 5%) was found within the bare tungsten tube. On the other hand, modification with 100 µg of Pt, Ir and Re, respectively, enhanced significantly the efficiency of trapping. Platinum-treated tubes were very efficient at collecting hydrides in the low temperature range of 100–200 °C, reaching efficiency close to 100%. Iridium- and rhenium-treated tubes were capable of trapping hydrides in the high temperature range of 700–900 °C, approaching an overall efficiency of 10%. Palladium modifier caused fatal deterioration of the tungsten tube. Low- and high-temperature mechanisms of trapping on the inner tube surface were seen, which were probably related to the low temperature dissociative chemisorption of hydrides and to the thermal decomposition of hydrides with simultaneous adsorption of products on the surface, respectively. Radiography experiments proved that the major part of selenium was collected at low temperature on a relatively small area in the central part of the platinum-treated tube opposite the injection hole. On the other hand, selenium collected at higher temperatures was found in a more diffuse area when iridium-treated and bare tubes were used. The following analytical figures of merit were found when sequestrating hydrides of selenium and arsenic within a platinum-treated tube: characteristic masses of 74 and 31 pg Se, 27 and 14 pg As pertaining to integrated absorbance and absorbance height of the signal, respectively; and limits of detection, based on 3 s-criterion, of 150 pg As and 270 pg Se were achieved. They related to a sample volume of one millilitre and fluctuation of overall blanks. The useful lifetime of platinum modified tubes reached 250 firings under optimum conditions.

Determination of arsenic by continuous hydride generation with direct introduction into an O 2 -argon microwave plasma torch atomic emission spectrometer

The determination of arsenic was studied with a simple and economic method. A continuous hydride generation system is interfaced to a microwave plasma torch atomic emission spectrometer (MPT-AES). Arsenic hydride is transferred directly and continuously by the carrier gas into the plasma torch without separation of hydrogen. When oxygen is introduced into the outer tube of the plasma torch, the plasma is more stable and has a higher tolerance to hydrogen. The detection limit (3σ) is 5.2 μg/L when the forward power is 100 W with argon as support gas. Application to the standard sample coal fly ash showed a comparable result to the certified quantity.

GaAs/H2O2 Electrochemical Interface Studied In Situ by Infrared Spectroscopy and Ultraviolet−Visible Ellipsometry Part II: Chemical Origin of Cathodic Oscillations

Changes in the interfacial chemical composition of n-GaAs(100) electrodes during cathodic reduction of H2O2 solutions (pH 0) at fixed potential are monitored in real time using in situ infrared spectroscopy and in situ spectroscopic ellipsometry. Under conditions in which the current density spontaneously oscillates, synchronous oscillations are observed in the thickness of a porous layer of solid arsenic hydride, with typical variations of a few hundred A. A physical and chemical model is proposed that accounts mathematically for the detailed time- and potential-dependent behavior and gives intuitive understanding of the chain of events occurring during an oscillation cycle. The periods of slow current rise correspond to the growth of the electro-active arsenic hydride phase, on which H2O2 is cathodically reduced. The current peaks coincide with the sudden dissolution of arsenic hydride, when the local potential reaches a value at which the phase is no longer cathodically protected, due to ohmic potentia...

GaAs/H2O2 Electrochemical Interface Studied In Situ by Infrared Spectroscopy and Ultraviolet−Visible Ellipsometry Part I: Identification of Chemical Species

Chemical species at the electrochemical interface between n-GaAs(100) and H2O2 in 0.5 M H2SO4 are identified by in situ infrared spectroscopy and in situ ultraviolet−visible ellipsometry. Under anodic conditions, H2O2 dissolves GaAs chemically, and the surface appears rough but clean of other phases. The sulfate concentration near the surface increases to compensate for the charge of the Ga3+ ions produced by dissolution. Under cathodic conditions, H2O2 is reduced electrochemically, but chemical GaAs dissolution is never completely suppressed; both dissolution products are indirectly detected, the Ga3+ ions because they lead to an increase in the local sulfate concentration and HAsO2 because part of it is reduced cathodically, giving islands of a solid arsenic hydride, most likely As2H2. Variations in the amount of As2H2 and its surface coverage by adsorbed H and OH groups affect the H2O2 reduction rate. A kinetic model is proposed for the interfacial chemistry and electrochemistry. Numerical simulations reproduce the main features of experimental current−potential scans, including the presence of a negative slope region related to oscillatory behavior.

False Lines due to Folding in Fourier Transform Spectroscopy

The phenomenon of false lines due to folding in Fourier Transform Spectroscopy is explained using by Nyquist sampling theorem The characters of false lines are discussed. The key to avoid false lines is to use suitable filters to remove the signal outside the wanted spectral region. Two kinds of filters, optical and electrpnic filters namely, are compared to serve this purpose. It is found out that both kind of filters should be combined in order to prevent folding as well as secure a good signal to noise ratio. Some experimental parameters setting rules are advanced. The method proved to be successful in our experiments of recording the v= 3 and v=4 highly vibrational spectra of arsine.

Hydrogen adsorption on GaAs (001) reconstructions

Hydrogen adsorption on the c(4×4), (2×4), (2×6), and (4×2) reconstructions of GaAs (001) have been characterized by internal-reflection infrared spectroscopy. The infrared spectra contain up to 15 bands due to the stretching vibrations of arsenic hydrides (2150–1950 cm−1), terminal gallium hydrides (1950–1800 cm−1), and bridging gallium hydrides (1800–950 cm−1). These features arise from hydrogen adsorption on arsenic and gallium dimers, and second-layer arsenic and gallium atoms. The large number of peaks observed indicates that the surface atoms exist in a variety of different chemical environments.

From New Zirconium-Phosphanide to Phosphinidene Complexes

Lithiated primary silylphosphanes and -arsanes react with rircOnocene-chloride-hydride to give planar Zr(III)2-E2-ringsystems (R = SiMc2Thex (I), Si(i-Pr)3, SiF(t-Bu)Is). However, the complexes can also be synthesized by conversion of zirconocene-dichloride with lithiated silylphosphanes. Reductive dehydrogenation of 1 through heating with Pd on activated charcoal or [(Ph3P)2Pt(C2H4)] in toluene leads to 2.

Selective medium reactions for the `arsenic(III)', `arsenic(V)', dimethylarsonic acid and monomethylarsonic acid determination in waters by hydride generation on-line electrothermal atomic absorption spectrometry with in situ preconcentration on Zr-coated graphite tubes

Methods were developed for the trace determination of total arsenic, `As(III)', `As(V)', dimethylarsonic acid (DMAA) and monomethylarsonic acid (MMAA) in sea and hot-spring waters by hydride generation/trapping and atomization in a graphite furnace using coated graphite tubes. Selective medium reactions were used to generate selectively hydrides of each arsenic species: 1. reduction with NaBH 4 in thioglycollic acid medium (total arsenic); 2. reduction with NaBH 4 in hydrochloric acid medium (inorganic arsenic, `As(III)' and `As(V)'); 3. reduction with NaBH 4 in citric acid/sodium hydroxide buffer (`As(III)'); and 4. reduction with NaBH 4 in acetic acid (`As(III)' and DMAA). The `As(V)' and MMAA can be evaluated by difference. Iridium, tungsten and zirconium-coated graphite tubes were investigated for the in situ preconcentration of arsenic hydrides. Trapping onto Zr-coated graphite tubes offers the best analytical performances, with detection limits of 56 ng l −1 for total arsenic (first selective medium reaction); 50 ng l −1 for inorganic arsenic and `As(III)' and DMAA (second and fourth selective medium reaction), and 80 ng l −1 for `As(III)' (third selective medium reaction).

‘Ars Sine Arte:’ Nicholas Lemery and the End of Alchemy in Eighteenth-Century France

‘Ars Sine Arte:’ Nicholas Lemery and the End of Alchemy in Eighteenth-Century France

‘Ars Sine Arte:’ Nicholas Lemery and the End of Alchemy in Eighteenth-Century France

L'A. demontre comment Nicholas Lemery a initie la cession de l'alchimie en France a la fin du XVIII e siecle, en limitant la definition de l'alchimie a une speculation fantastique

Characteristics of the atomic fluorescence signals of arsenic in speciation studies

The behaviour of the arsenic hydrides, generated after the speciation of AsIII (arsenite), MMAs (monomethylarsonate) and DMAs (dimethylarsinate), in an atomic fluorescence cell was investigated. The efficiency of the hydride generation process was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) after sampling the liquid drain of the gas–liquid separator and by a gas chromatograph with mass spectrometric detection (GC-MS) for the analysis of the sampling gas of the separator. The different concentrations at which the fluorescence signal reaches a maximum were determined for each As species.