Atomic fluorescence spectrometry with laser excitation

A laser atomic fluorescence spectrometry for the detection of trace concentrations of the elements is described. The detection limits for Pb, Fe, Na, Pt, Ir, Eu, Cu, Ag, Co and Mn in aqueous solutions obtained at present are the best ones for the rapid spectral analytical methods. The analytical potentials of the laser spectrometer are exemplified by the analysis of real samples of different chemical composition.     

Solvent-derived metal oxides in electrospray mass spectrometry of metal salt solutions

The electrospray mass spectra of MX₂and MX₃salts (where X is typically halide or nitrate) in protic and aprotic solvents, and solvent mixtures were examined. Comparisons of species responses with equilibrium aqueous solution concentrations were made. For MX₂salts, a good correlation between MOH⁺ response and MOH⁺ solution concentration was observed under conditions where the collision energy was nominally zero. Cu(II) is easily reduced in acetonitrile to Cu(I); Cu(I) was the principal species observed in the electrospray mass spectrum of Cu(II) in acetonitrile whereas Cu(II) was the principal species observed in that of Cu(II) in dimethyl sulphoxide. Gas-phase reactions between solvated clusters produced by electrospray and a second solvent vapour were examined. M³⁺clusters were the principal ions observed when an aqueous solution of MX₃was sprayed in the presence of aprotic solvent vapours.     

Atomic layer deposition of metal oxides on pristine and functionalized graphene

We investigate atomic layer deposition (ALD) of metal oxide on pristine and functionalized graphene. On pristine graphene, ALD coating can only actively grow on edges and defect sites, where dangling bonds or surface groups react with ALD precursors. This affords a simple method to decorate and probe single defect sites in graphene planes. We used perylene tetracarboxylic acid (PTCA) to functionalize the graphene surface and selectively introduced densely packed surface groups on graphene. Uniform ultrathin ALD coating on PTCA graphene was achieved over a large area. The functionalization method could be used to integrate ultrathin high-kappa dielectrics in future graphene electronics.     

An overview of electrothermal excitation sources for atomic emission spectrometry

Electrothermal devices have been employed in analytical atomic spectrometry for more than four decades. Normally these resistively heated devices are used to provide an atomic cloud that is either probed by an external light source (atomic absorption and atomic fluorescence) or swept into a second excitation source such as the inductively coupled plasma (electrothermal vaporization). Less commonly, the electrothermal device both produces the atomic vapor and excites the emission of the atoms in the cloud. This brief review, with 65 selected references, will describe those occasions where electrothermal devices are indeed employed in this manner, with no other source of excitation energy applied. Beginning with a graphite furnace system described in 1975 and ending with a tungsten coil application published in 2008, analytical figures of merit will be reported for methods involving devices fabricated from carbon, molybdenum, and tungsten. The review ends with a discussion of the practical limitations associated with these techniques.     

Chemical analysis by inductively coupled plasma atomic emission spectrometry of semiconducting ceramics of barium titanate doped with various metal oxides

The Ba and Ti macroconstituents as well as the impurities and dopants content (Al, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Si, Sr, W, Zn and Zr) in a dense (> 98% theoretical) barium titanate sample have been determined by inductively coupled plasma-atomic emission spectrometry after one of these decomposition routes: (a) decomposition with HCl in a PTFE-lined pressure vessel, (b) fusion with Na₂CO₃ in a platinum crucible, and (c) fusion with Li₂B₄O₇ in a graphite crucible. Matrix effects were taken into account. Detection limits for minors and trace elements were determined. High sensitivity and good precision were attained.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Low-temperature emission of singlet oxygen from the surface of transition metal oxides

Low-temperature emission of the singlet form of dioxygen ¹O₂ from the surface of the individual and mixed V and Mo oxides was detected by thermal desorption at 20–350°C. The amount of the desorbing ¹O₂ and the temperature range of ¹O₂ emission were found to depend on the composition of the catalyst; the low-temperature ¹O₂ form can be regenerated after its contact with oxygen.     

Interference effects in a capillary arc excitation source for emission spectrometry

The effects of major constituents (K, Zn, and phosphate) on the emission intensities of eighteen selected analytes in a d.c. capillary arc plasma provided with a nebulizerdesolvation apparatus, are reported. Potassium and zinc enhance the emission from most of the analytes, especially that from the elements of medium ionization potential. Cesium added in excess as a buffer reduces the cation interferences to negligible proportions. The presence of phosphate results in a marked decrease in the excitation temperature of the plasma. Depression effects of phosphate, observed for all the analytes tested but Mg, Se, and La, are probably due to the reduced temperature.     

Trace metal assay of thorium oxide by atomic emission spectrometry

Summary An Atomic Emission Spectrometric (AES) method has been developed for the direct determination of twenty-two metallic elements at trace concentrations in thorium oxide. The method is based on the use of a d.c. arc — carrier distillation technique with 12% composition of a mixed carrier, viz. AgCl+SrF₂ in 5:1 proportion, and is equally applicable to both volatile and refractory analytes. A direct reading emission spectrometer with computerised data acquisition and processing facility has been used in these studies. The standardisation procedure includes study of volatilisation/excitation characteristics of the analyte elements to optimise choice and proportion of the carrier and signal integration time apart from optimisation of other experimental parameters such as arc current, viewing position of the arc plasma, sample charge etc. The detection limits for the analytes lie in the range 0.1–50 ppm while the precision of determinations is better than 15% for most of the elements as evaluated from the repetitive analyses of spiked samples.     

Dissociation of 1,1,1-trifluoroethane behind reflected shock waves: shock tube/time-of-flight mass spectrometry experiments

The dissociation of 1,1,1,-trifluoroethane, a potential non-RRKM reaction, has been studied at 600 and 1200 Torr and high temperatures (1500-1840 K) using a new shock tube/time-of-flight mass spectrometer (ST/TOF-MS). These data obtained by an independent method are in good agreement with the laser schlieren, LS, experiments of Kiefer et al. [J. Phys. Chem. A 2004, 108, 2443-2450] and extend the range of that experimental dataset. The data have been simulated by both standard RRKM calculations and the non-RRKM model reported by Kiefer et al. but with = 750 cm(-1). Both the RRKM and non-RRKM calculations provide equally good fits to the ST/TOF-MS data. Neither model simulates the combined ST/TOF-MS and LS datasets particularly well. However, the non-RRKM model predicts a pressure dependency closer to that observed in the experiments than the RRKM model.     

Measuring metal substrate roughness with glow discharge optical emission spectrometry

Although there are many methods to evaluate metal surface roughness, it is difficult to detect the substrate roughness of coated samples. Depth profile analysis (DPA) is proposed as a new method for the substrate roughness measurement, and glow discharge optical emission spectrometry (GDOES) becomes a candidate in substrate roughness measuring instruments. With this method, the typical roughness parameters R_a (arithmetic mean of the absolute deviation values of the roughness profile) and R_y (maximum value of consecutive peak and valley heights of the roughness profile along the sampling length) can be easily obtained. The principle of this method is discussed and the formulasof the principle are deducted in this paper. Electrodeposited zinc coating on copper substrate specimens is used as an example to explain the measuring process. Copyright © 2007 John Wiley & Sons, Ltd.     

Intensity of thermal radiation of metal spectra in flame emission spectrometry

A unified and well-referenced approach to the derivation of the total intensity of spectral lines of atoms excited by flame in thermal equilibrium is given. Expressions for the total intensity for atoms at low and high concentrations are given. The influence of self-absorption and self-reversal on the spectral line contour and on analytical curves is discussed. Application of the derived equations to emitting atoms in arcs and to molecules in flames is also considered.     

Atomic and ionic fluorescence spectrometry with pulsed dye laser excitation in the inductively-coupled plasma

The atomic and ionic fluorescences of iron, tin, barium and indium excited by flash-lamp-and nitrogen laser-pumped pulsed dye lasers in the inductively-coupled plasma (ICP) are studied. Noise sources are investigated and detection limits are compared to the techniques of ICP-emission and laser-excited atomic fluorescence spectrometry.     

Robotic preparation of metal samples for analysis by plasma emission spectrometry

Summary A method utilizing a laboratory robotic system to automate sample preparation for the chemical analysis of metals was developed. Anticipated elemental concentration values for samples are entered into the robotic system, and the system determines the needed sample weights and calibration solution concentrations. The robot then weighs, dissolves, and dilutes the samples and prepares calibration solutions prior to multi-elemental analyses by inductively-coupled plasma — atomic-emission spectrometry. Zinc-base alloy standard reference materials were used to evaluate this method. For a batch of ten samples, operator times compared with a similar manual method were reduced by about 5-fold. Precision and accuracy data for samples prepared by robotic and manual methods were equivalent.

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Automatische Probenvorbereitung für die Analyse durch Plasma-Emissions-Spektrometrie mit Hilfe eines Laborroboters

     

Atomic fluorescence flame spectrometry using a mercury line source

The possibility of exciting the fluorescence of several elements with the “overlapping” lines of other elements and the effectiveness of exciting the fluorescence of Fe, Mn, Ni, Cr, Tl, Cu and Mg with a 90 W mercury discharge lamp, are discussed. A method of increasing the fluorescence radiation by suitable optics, with a simple adaptation of a Jarrell-Ash AA spectrometer, is described. A two-pass system of the incident radiation into the flame is coupled with a mirror, in the optical axis, which reflects the fluorescence radiation emitted at the opposite side to the monochromator slit. This produces an increase of 168% of the signal. Detection limits for 10 elements are reported.     

Highly stable mesoporous metal oxides using nano-propping hybrid gemini surfactants

Noble Gemini surfactants containing a siloxane moiety have been designed and successfully synthesized in the present study and are utilized as structure-directing agents for mesoporous metal oxides such as zirconia, titania, and vanadia. The siloxane moiety is believed to play an important nano-propping role during the surfactant removal by direct calcination, yielding thermally stable mesoporous metal oxides. It is also believed that the synthesis strategy described here can be applied to the synthesis of robust nanostructured materials such as nanoparticles and nanorods in addition to mesoporous materials.     

Atomic absorption studies using a hollow-cathode tube as an absorption source

When hollow-cathode tubes are used as the emission source and as the absorption source, atomic absorption studies reveal microgram quantities of several elements; sodium, magnesium, calcium, beryllium, and silicon were detected in the discharge of the absorption tube. Conventional, independent circulating systems and d.c. power supplies, were used with each tube, along with other readily available equipment. An analytical curve plotted for sodium over the range 0—100 μg, obeys Beer's law. Lithium and magnesium suppress the sodium absorption values, thus careful standardization is necessary. The average percent deviation from the mean for a number of sodium samples analyzed was ± 8.0%.     

Determination of major constituents in metal samples by emission spectrometry using a demountable hollow cathode source and internal standardization

Results are given for the emission spectrometric determination of major constituents of metal samples. The source used permits rapid interchange of sample, which is in the form of a hollow cathode. A method of internal standardization is employed, which permits accurate determinations of concentration to be made without the need for a complete analysis of the sample. Copper and zinc in brass may be determined with an accuracy comparable with that for ICP, as can nickel, chromium and iron in stainless steel.     

A growth mechanism for carbon nanotubes using metal oxides as catalysts

Metal oxides have only recently begun to be used as catalysts for the growth of carbon nanotubes. Here, we propose a new model for the growth of carbon nanotubes, based on the intra‐granular charge transfer transition and the lattice strain of the catalyst nanoparticles. This is supported by results obtained from the doped metal oxides like samarium doped zinc oxide (SmZnO) and terbium doped zinc oxide (TbZnO). The intragranular charge transfer transition is believed to be responsible for the dissociation of the hydrocarbon molecules. The lattice strain of the catalyst nanoparticles appears to be responsible for the diffusion of carbon atoms through the catalyst particles.