Determination of Thallium by Graphite Furnace- Atomic Absorption Spectrometry with Atomization Under Pressure

Abstract

Atomization under pressure worsens peak height sensitivity of both the 276.79 and the 377.57 nm resonance lines. Peak area is also worsened as atomization pressure increases, though much less than peak height.

Atomization under pressure alters peak times. Most notable is the prolongation of mean residence time and delay of peak time. As a consequence of this vapor phase interferences are reduced.

Linearity of calibration curves is improved by pressure.     

Direct As,Bi, Ge,Hg and Se(IV) cold vapor/hydride generation from coal fly ash slurry samples and determination by electrothermal atomic absorption spectrometry

Direct cold vapor and hydride generation procedures for As, Bi, Ge, Hg and Se(IV) from aqueous slurry of coal fly ash samples have been developed by using a batch mode generation system. Ir-treated graphite tubes have been used as a preconcentration and atomization medium of the vapors generated. A Plackett–Burman experimental design has been used as a strategy for evaluation of the effects of several parameters affecting the vapor generation efficiency from solid particles, vapor trapping and atomization efficiency from Ir-treated graphite tubes. The effects of parameters such as hydrochloric acid and sodium tetrahydroborate, argon flow rate, trapping and atomization temperatures, trapping time, acid solution volume and mean particle size have been investigated. The significant parameters obtained (trapping and atomization temperatures for As and Ge; trapping temperature and trapping time for Bi; argon flow rate and atomization temperature for Se) have been optimized by 2²+star central composite design. For Hg, the trapping temperature has been also significant. Optimum values of the parameters have been selected for the development of direct cold vapor/hydride generation methods from slurry particles. The accuracy of methods have been verified by using NIST-1633a coal fly ash certified reference material. Absolute detection limits of 11.5, 48.0, 600, 55.0 and 11.0 ng l⁻¹ for As, Bi, Ge, Hg and Se have been achieved, respectively. A particle size less than 50 μm has shown to be adequate to obtain total cold vapor/hydride generation of metals content in the aqueous slurry particles.     

Determination of silver by graphite furnace—atomic absorption spectrometry with atomization under pressure

Summary When determined with pressurized atomization silver shows a lower peak height sensitivity than under normal conditions. Peak area is less influenced by pressure. The peak parameters are somewhat changed as compared to normal atomization. Notable is the prolongation of the mean residence time and peak time. Interferences are reduced with atomization under pressure.The linearity of the calibration curves is extended with atomization under pressure.

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Silberbestimmung im Graphittiegel. Atomabsorptions-Spektrometrie nach Zerstäubung unter Druck

Zusammenfassung Bei Zerstäubung unter Druck zeigt Silber eine geringere Empfindlichkeit der Peak-Höhe. Die Peak-Fläche wird durch Druck weniger stark beeinflußt. Im Vergleich zur Normalzerstäubung sind die Peak-Parameter etwas verändert, die Störungen sind bei Zerstäubung unter Druck geringer, die Eichkurven verlaufen über größere Strecken geradlinig.

     

A possible steady state kinetic model for the atomization process during flame atomic spectrometry: Application to atomization interference effects of aluminum on Group II elements

The atomization interference effects of AlCl₃ on MgCl₂ and CaCl₂ during flame atomic absorption spectrometry were studied in terms of a steady state kinetic model which takes into account relative rates of thermal dissociation of analyte and interferant metal salts, recombination of counter atom and analyte and interferant atoms, charge transfer between analyte and interferant species, and ion/electron collisional de-ionization within the plasma. Data are presented showing that the interference of AlCl₃ on the atomization of MgCl₂ and CaCl₂ in an air-acetylene flame is due (a) to interference effects due to AlCl₃ which occur prior to complete atomization of the Group II metal chlorides, and (b) to the recombination of the Group II metal and the chlorine atom which is enhanced by the increased density of the chlorine atom as a result of the dissociation of the AlCl₃ interferant.     

Bond energies and the enthalpies of formation of mono- and polyradicals in nitroakanes 3. Nitroalkanes C<Subscript>4</Subscript>–C<Subscript>7</Subscript>

Based on the experimentally determined values and published data, the enthalpies of formation of nitroalkanes C₄–C₇ in the standard state and in the gas phase were recommended. The dissociation energies of bonds in these compounds were determined taking into account the enthalpies of atomization and the energies of nonvalent interactions of nitro groups with one another. The calculated values were compared with the available thermal decomposition kinetic data. The dissociation energies of bonds in C₄–C₇ nitroalkane radicals were also calculated using the enthalpies of atomization and the energies of nonvalent interactions of nitro groups. Regularities of changes in the bond dissociation energies of nitroalkanes C₁–C₇ and their radicals are established.     

A possible steady state kinetic model for the atomization process during flame atomic spectrometry: Application to atomization interference effects of aluminum on Group II elements

The atomization interference effects of AlCl₃ on MgCl₂ and CaCl₂ during flame atomic absorption spectrometry were studied in terms of a steady state kinetic model which takes into account relative rates of thermal dissociation of analyte and interferant metal salts, recombination of counter atom and analyte and interferant atoms, charge transfer between analyte and interferant species, and ion/electron collisional de-ionization within the plasma. Data are presented showing that the interference of AlCl₃ on the atomization of MgCl₂ and CaCl₂ in an air-acetylene flame is due (a) to interference effects due to AlCl₃ which occur prior to complete atomization of the Group II metal chlorides, and (b) to the recombination of the Group II metal and the chlorine atom which is enhanced by the increased density of the chlorine atom as a result of the dissociation of the AlCl₃ interferant. Received: 23 February 1998 / Revised: 18 December 1998 / Accepted: 25 December 1998     

Disk-Ended Atomizer for Graphite Furnace Atomic Absorption Spectrometry

Abstract

The Disk-Ended Atomizer (DEA) is a technique for spatially isothermal atomization with an improved temporal isothermality of the atomization zone. It was developed at Sofia University as a continuation of our studies^1,2 concerning one of the most important problems of graphite furnace atomic absorption spectrometry - the problem of isothermal atomization. DEA has a simpler design then many other techniques for isothermal atomization (L′vov cuvette³, Woodriff furnace^4,5, capacitive discharge technique⁶, two-step furnaces^2,7,8, etc.) and can be readily used with any commercial spectrophotometer.     

Thermochemical Study of Gaseous Salts of Oxygen-containing Acids: X. Potassium and Rubidium Bismuthites

The vapor formation of potassium, strontium bismuthites was studied by Knudsen's methodwith a gas phase mass-spectrometric analysis. The standard enthalpies of formation and atomization ofgaseous KBiO₂ and RbBiO₂ were determined.     

An Inexpensive Probe for Sample Introduction in Electrothermal Atomization Atomic Absorption Spectrometry

Abstract

An inexpensive probe system for introduction of samples for analysis by electrothermal atomization atomic absorption spectrometry is described. The system involves mounting a capillary tube on a tripod stand to allow the probe to be inserted into the atomizer for analysis. Comparison between this method of atomization and conventional atomization off the atomizer wall for the measurement of cadmium is described.     

Atom formation mechanisms of As with different techniques in atomic absorption spectroscopy

In this work, the atomization mechanism of As in flameless atomic absorption spectroscopy is investigated with both direct injection of the analyte into the furnace and with the well-known hydride generation method. The proposed mechanisms are controlled by the variation of the obtained signals with various pre-heating programmes of the furnace. In the direct injection method, it is found that arsenic is vaporized to AsO and atomized by the dissociation of the oxide. In the hydride generation technique however, the formed AsH₃ is decomposed on the graphite surface before the atomization temperature is reached and the metallic arsenic is vaporized as As₄, which is then decomposed to As₂ dimers and atomized by gas-phase dissociation.     

Electrothermal atomic absorption spectrometry with two-step probe atomization and primary absorption signal feedback

A method is proposed to reduce the relative detection limits for elements in an atomic absorption spectrometer with a graphite furnace and two-step probe atomization, based on using feedback between the absorption impulse of primary sample atomization and probe fixation in the position for vapor fractionation. Deposition of sample fractions on the probe, which interferes with measuring the analytical signal, is reduced. The relative limits of the direct detection of Pb, Cd, and Tl in NaCl and K₂SO₄ are lowered by more than one order of magnitude in comparison to the atomization of such salts under the conditions of a temperature-stabilized furnace with a platform. The detection limits are 10^?7 to 10^?8 wt %. The relative standard deviation of the analytical signals does not exceed 5%, which is appropriate for the measurement of concentration.     

The Beryllium Pentamer: Trailing an Uneven Sequence of Dissociation Energies

Recent high‐resolution spectroscopic studies by Merritt, Bondybey, and Heaven (Science 2009 , 324, 1548) have heightened the anticipation that small beryllium clusters will soon be observed in the laboratory. Beryllium clusters are important discrete models for the theoretical study of metals. The trigonal bipyramidal Be₅ molecule is studied using high‐level coupled cluster methods. We obtain the optimized geometry, atomization and dissociation energies, and vibrational frequencies. The c～CCSDT(Q) method is employed to compute the atomization and dissociation energies. In this approach, complete basis set (CBS) extrapolations at the CCSD(T) level of theory are combined with an additive correction for the effect of iterative triple and perturbative quadruple excitations. Harmonic vibrational frequencies are obtained using analytic gradients computed at the CCSD(T) level of theory. We report an atomization energy of 129.6 kcal mol^?1 at the trigonal bipyramid global minimum geometry. The Be₅→Be₄+Be dissociation energy is predicted to be 39.5 kcal mol^?1. The analogous dissociation energies for the smaller beryllium clusters are 64.0 kcal mol^?1 (Be₄→Be₃+Be), 24.2 kcal mol^?1 (Be₃→Be₂+Be), and 2.7 kcal mol^?1 (Be₂→Be+Be). The trigonal bipyramidal Be₅ structure has an equatorial–equatorial bond length of 2.000 Å and an axial–equatorial distance of 2.060 Å. Harmonic frequencies of 730, 611, 456, 583, 488, and 338 cm^?1 are obtained at the CCSD(T)/cc‐pCVQZ level of theory. Quadruple excitations are found to make noticeable contributions to the energetics of the pentamer, which exhibits a significant level of static correlation.     

石墨炉原子化器中原子化过程的研究(Ⅲ)——石墨炉中锗的原子化机理

有关锗的石墨炉原子吸收光谱分析,文献报道较少,对锗的原子化机理,亦有不同的看法^[1~3].本文基于右墨炉中锗原孚化行为的观察,对锗原子形成的过程进行了讨论,认为原子化过程中,并存着二种还原反应:GeO₂(s)+C→GeO(g)+CO(g),GeO₂(s)+CO→GeO(g)+CO₂,而锗原子的形成是GeO(g)热分解的结果。     

High Pressure Super-Heated Electrospray Ionization Mass Spectrometry for Sub-Critical Aqueous Solution

The heating of electrospray ion source under atmospheric pressure is limited to the normal boiling point of the solution. The boiling takes place when the vapor pressure of the liquid at a given temperature equals the ambient pressure. By using a high pressure ESI source, which has been developed previously in our laboratory, a stable electrospray ionization of super-heated aqueous solution is performed up to a solution temperature of 180°C. The ion source is pressurized with pure nitrogen to a maximum pressure of 11 atm, and it is coupled to a commercial mass spectrometer via a custom-made ion transport capillary. A booster pump with variable pumping speed is added to the pumping system to regulate the pressure in the first pumping stage at 1?~?1.3 Torr. High pressure mass spectrometry is performed on several peptides and proteins to demonstrate its application in the temperature-controlled thermally induced denaturation and dissociation. Graphical Abstract

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Determination of cadmium by electrothermal atomic absorption spectrometry after microwave-assisted digestion of animal tissues and sewage sludges

The determination of cadmium in different sample types has been carried out by electrothermal atomization atomic absorption spectrometry with D₂-background correction using a unpyrocoated graphite tube, after pressurized microwave-assisted digestion. Five chemical modifiers [(NH₄)₂HPO₄, Pd(NO)₃)₂, Ni(NO₃)₂, thiourea and Triton X-100] have been assayed and nickel nitrate has been found to be most effective for an accurate determination of cadmium in mussel tissue, pig kidney and sewage sludge. The characteristic mass of the method is of the order of 1 pg and the limit of detection is lower than 0.1 ng/ml.     

Organic,inorganic and total mercury determination in fish by chemical vapor generation with collection on a gold gauze and electrothermal atomic absorption spectrometry

A method for organic, inorganic and total mercury determination in fish tissue has been developed using chemical vapor generation and collection of mercury vapor on a gold gauze inside a graphite tube and further atomization by electrothermal atomic absorption spectrometry. After drying and cryogenic grinding, potassium bromide and hydrochloric acid solution (1 mol L^− 1 KBr in 6 mol L^− 1 HCl) was added to the samples. After centrifugation, total mercury was determined in the supernatant. Organomercury compounds were selectively extracted from KBr solution using chloroform and the resultant solution was back extracted with 1% m/v L-cysteine. This solution was used for organic Hg determination. Inorganic Hg remaining in KBr solution was directly determined by chemical vapor generation electrothermal atomic absorption spectrometry. Mercury vapor generation from extracts was performed using 1 mol L^− 1 HCl and 2.5% m/v NaBH₄ solutions and a batch chemical vapor generation system. Mercury vapor was collected on the gold gauze heated resistively at 80 °C and the atomization temperature was set at 650 °C. The selectivity of extraction was evaluated using liquid chromatography coupled to chemical vapor generation and determination by inductively coupled plasma mass spectrometry. The proposed method was applied for mercury analysis in shark, croaker and tuna fish tissues. Certified reference materials were used to check accuracy and the agreement was better than 95%. The characteristic mass was 60 pg and method limits of detection were 5, 1 and 1 ng g^− 1 for organic, inorganic and total mercury, respectively. With the proposed method it was possible to analyze up to 2, 2 and 6 samples per hour for organic, inorganic and total Hg determination, respectively.     

Multireference CCI calculations on the bond distance and dissociation energies of methane

Large CAS SCF and multireference CCI calculations have been performed on CH₄ to determine the bond distance, the CH bond dissociation energy and the atomization energy. The best calculatid dissociation energies are in excellent agreement with experiments with relative errors of 2% and less, but the discrepancy between theory and experiment for r_e in methane remains. The same problem is found for r_e in CH₃.     

Determination of standard enthalpy of vaporization and thermal decomposition reactions from derivative thermogravimetric (DTG) curves

The paper proposes the use of the derivative thermogravimetric (DTG) curve for the acquisition of equilibrium vapor pressure and dissociation pressure for the materials and derivation of their standard enthalpy of formation from single DTG curve recorded under optimum experimental conditions, such as heating rate and the sweep rate of the carrier gas passed over the sample. The vapor pressure and the standard enthalpy of sublimation (Δ_subH ° _298.15) of CdI₂ and the dissociation pressure and the standard enthalpy of formation of CaCO₃ derived from their DTG curves are found to be in good agreement with the best assessed values reported in the literature.     

Electrostatic Accumulation Furnace for Electrothermal Atomic Spectrometry (E. A. F. E. A. S.)

Abstract

A new technique is described for rapid elemental analysis of atmospheric particulates. The basic principle is direct deposition of atmospheric particulate matter in a furnace for electrothermal atomization and analysis by atomic absorption spectrometry. A prototype instrument has been tested by analyzing the lead content in the laboratory atmosphere.