Atom Reservoir Research Articles

Electrothermal Vaporization for Sample Introduction in Atomic Emission Spectrometry

The importance of trace elements in environmental, nutritional, clinical, forensic, toxicological, and other fields has been well recognized. Among the variety of analytical techniques available for trace element determinations, atomic spectrometry is one of the most popular. This technique may further be divided into atomic absorption, atomic emission, and atomic fluorescence, with the latter two more amenable to multielement analyses. These atomic techniques require the introduction of samples into a high-temperature atom reservoir where atomic (or ionic) vapors are produced. These high-temperature atom sources include flames; the inductively coupled plasma, ICP; microwave-induced plasma, MIP; direct current plasma, DCP; and the graphite furnace.

Systematics of multielement determination with resonance ionization mass spectrometry and thermal atomization

The systematics for multielement determination using resonance ionization mass spectrometry and thermal atomization is developed. The aspects of atomization, ionization, and detection are discussed and resonance ionization is demonstrated for 19 elements. The selective, sequential ionization of seven elements from a single sample is also demonstrated. A one-wavelength, two-photon ionization scheme generally is used in which the first photon excites a bound transition in the near-ultraviolet region and second photon promotes the electron into theionization continuum. The wavelength-dependence ion formation from the thermally produced atom reservoirs is demonstrated for these elements by scanning a Nd:YAG-pumped dye laser across its tunable wavelength range. The observed wavelengths where ionization occurs have been correlated where possible with allowed transitions between known electronic energy levels. The elements accessible by using four common dyes are tabulated. More than 20 elements are accessible within the wavelength range of each dye.

Burnt [sbnd]gas composition of the helium [sbnd]oxygen [sbnd]acetylene flame

The burnt gas composition of a potentially important atom reservoir, the He O 2 C 2H 2 flame, is calculated. This flame, compared to the air—acetylene flame, provides a slightly more reducing and a much less quenching environment.

Evaluation of Atomic Fluorescence Detection Limits with an Inductively Coupled Plasma as an Excitation Source and Atomization Cell

The use of an inductively coupled plasma, ICP, as an excitation source for atomic fluorescence spectrometry, AFS, in a second ICP is re-examined. Improvements in the ICP-ICP-AFS setup have allowed the lowering of the limits of detection by one to two orders of magnitude below that of previous work. Also discussed is a new mode of operation for the atomization cell ICP. Through simple torch-position and flow-rate adjustments, a thin plasma, which extends 20 to 30 cm above the torch, can be produced. This plasma is referred to as the pencil plasma. With the use of these operating conditions, propane can be added to the Ar nebulizing gas to aid in refractory-element determination. The pencil plasma and the conventional plasma will be compared for use as an atom reservoir for AFS measurements.

Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—II: Fluorescence characteristics and detection limits for fourteen elements

An account is given of the analytical characteristics of the elements Al, B, Ba, Ga, Mo, Pb, Si, Sn, Ti, Tl, V, Y, Zr and U in atomic and ionic fluorescence spectrometry using an excimer (XeCl) pumped pulsed dye laser as excitation source. The inductively coupled argon plasma was mainly used as atom/ion reservoir. The detection limits were found to be in the range 0.4–20 ng ml −1, improving “standard” tabulated ICP emission values by factors between 1 and 66. The separated air-acetylene flame and the carbon rod were also used as atom reservoir for a few volatile elements, the practical detection limit for lead with the latter being 6 × 10 −15g. The advantages and disadvantages of such an analytical system are discussed, one of the main advantages being certainly the high spectral selectivity of the technique.

Cyclopentadienyl(peralkylarene) iron(I) Complexes as H Atom Reservoirs: Isolation of Semihydrogenated Species in the Pd/C Catalyzed Hydrogenation of Cyclopentadienyliron(II) Complexes of Exocyclic Olefins

Cyclopentadienyl(peralkylarene) iron(<scp>I</scp>) Complexes as H Atom Reservoirs: Isolation of Semihydrogenated Species in the Pd/C Catalyzed Hydrogenation of Cyclopentadienyliron(<scp>II</scp>) Complexes of Exocyclic Olefins

Determination of Arsenic by Non-Dispersive Atomic Fluorescence Spectrometry Using a Sodium Borohydride Reduction Technique and Graphite Furnace Atomizer

Abstract The determination of arsenic through employing non-dispersive atomic fluorescence spectrometry that follows a hydride generation pretreatment technique has been investigated. A laboratory made graphite furnace atomizer was used as an atom reservoir. The detection limit of arsenic (III) was 0.01 ng. The linear analytical range covered about three orders of magnitude of concentration. The present method has been successfully applied to the determination of arsenic in steel samples.

Why not ICP as atom reservoir for AAS?

The sensitivity S A of determination by inductively coupled plasma atomic absorption spectrometry (ICP—AAS) is discussed. All important factors influencing S A are comprised in one single sensitivity formula, which allows an estimate to be made of the correct order of magnitude of S A for both flame—AAS and ICP—AAS measurements. The most important analytical factors are the degree of dissociation and ionization (0≤ f C , and f I ≤1), the dilution factor f D , which takes into account the dilution of the analysis element A by its transition from the solution to the ICP, and the absorption path length b. Like flame—AAS, an analytical approach using ICP—AAS has high selectivity and makes it possible to carry out determinations without chemical and ionization interferences. This important advantage of ICP—AAS in comparison to flame—AAS is based on the fact that the ideal condition f C →1 and Δ f→0 for the analysis and standard solutions can be much more easily realized in the ICP than in flames. Serious disadvantages of an ICP as an atomic reservoir for AAS are the reduced sensitivity and lower detection power compared to flame—AAS. The reduction of S A is caused mainly by the reduction of b/f D by a factor of about 0.1 and to a smaller degree by stronger broadening of the absorption line and the depopulation of the lower energy state of the atom A that absorbs the resonance radiation. The estimated S A value for A = Ag, Al, Ca, Cd, Co, Cr, Cu, Pd and Pt agree with the corresponding experimental values to within a factor of about 3. No experimental values could be obtained for B and Si. An application field of ICP—AAS is the analysis of complex compounds that are difficult to dissociate into atoms using flames. In these determinations, a high sensitivity is generally not needed but a good selectivity is important. Some applications are shown.

Non-dispersive atomic fluorescence spectrometry with a carbon filament atom reservoir

The non-dispersive atomic fluorescence spectrometric determination of Bi, Cd, Hg, Te, Tl and Zn on a carbon filament atom reservoir with electrodeless discharge lamp sources and reflecting microscope objective lenses is described. The non-dispersive system shows distinct advantages for an element such as tellurium whose principal fluorescence lines fall within the useful range of the solar-blind photomultiplier detector, and marginal advantages for mercury, cadmium and zinc where only one line is within the detector range. It is inferior for bismuth, thallium and lead where lines lie at the extremes of the useful detector range. The technique was applied successfully to the determination of cadmium (0.012%) in a copper-base alloy.

Chemical Interference Effects in the Atomic Absorption Spectrometric Determination of Lead with Premixed Inert Gas (Entrained Air)-Hydrogen Flames

Several authors have investigated so-called cool flames as atom reservoirs in atomic absorption spectrometry; these flames are usually entrained air-hydrogen flames in which the combustible gas (hydrogen) is diluted with the argon or nitrogen of a nebulizing gas. Such low temperature flames are well known to be very prone to chemical interferences. These chemical interferences could be eliminated by using the addition technique and the solvent extraction method. The present authors have also demonstrated that the premixed inert gas(entrained air)-hydrogen flames produced with the specially designed multi-flame burner can be used as suitable atom reservoirs for the determinations of zinc, tin, bismuth, arsenic and selenium, and gallium by atomic absorption spectrometry and that the chemical interferences encountered in their determinations can be removed by the addition of a large amount of lanthanum chloride, ferric chloride, magnesium chloride, and stannous chloride as interference-releasing agents.

Ultramicroanalysis of metals by means of an integrating atomic absorption spectrometer and a carbon filament atom reservoir.

A fast reacting atomic absorption spectrometer in combination with a carbon filament atom reservoir was used for ultramicroanalysis of calcium and magnesium. The analysis of 1 X 10(-12) mole of magnesium gave a variation of coefficient of +/-3% and analysis of 2 X 10(-11) mole of calcium gave one of +/-5%. The effect of adding various common biological substances to the samples in great excess was tested. No interference could be observed.

The determination of tin by carbon filament atomic absorption spectrometry

The atomic absorption characteristics of tin on a carbon filament atom reservoir are described. The behaviour of tin in aqueous solution astin(II) chloride, in xylene as tin octoate and in oil solutions is studied. The interferenceeffects of a selected range of seven cations, added as chlorides in aqueous solution or as naphthenates in non-aqueous media, and of sulphate and phosphate were examined. In all cases, the signals were measured in the filament reservoir with a surrounding hydrogen diffusion flame. The 1% absorption sensitivity in the organic media at the 286.3-nm line was 10 -10 g and 9·10 -11 g in aqueous solution. In the latter medium, the corresponding sensitivity at 224.6 nm was 6.7·10 -11 g. The linear analytical range lay in the region 0 to 20 ng.

Study of the determination of molybdenum by atomic absorption spectrometry using a carbon filament atom reservoir

A study is being made of the operating parameters and interferences in the atomic absorption determination of an element which is difficult to atomise (Mo) using a filament atom reservoir. A comparison is made with an element which is readily atomised (Zn). It is possible that this device is better suited in real situations to the determination of involatile elements such as Mo and in this instance especially using a hydrogen/nitrogen sheathing gas. There were numerous interferences in the case of Zn, but only tungsten produced a significant effect in the determination of Mo. The complete text of this paper has been published in Analytica Chimica Acta, 66 (1973) 171–178.

Theoretical temperature-time curves for electrically heated filament atom reservoirs : Their significance in analytical spectrometry

A simple theoretical approach has been used to calculate the temperature and power consumption versus time curves for graphite and tungsten filaments 25 mm × 1 mm radius operated at a number of different voltages. Results are also presented to show the effect of filament dimensions. These results suggest that there is scope for improvement in the design of filament atom reservoirs.

Trace analysis for sulphur and phosphorus in aqueous solution by a carbon filament atom reservoir technique

The chemiluminescent emissions of S 2 and HPO are excited around a resistively heated carbon filament in a hydrogen-nitrogen diffusion flame. Detection limits of 5 · lO -10 g and 4 · 10 -9 g were obtained, respectively, for sulphur and phosphorus for 1-μl samples of sulphuric and phosphoric acid solutions. Interference effects were studied; there are numerous cationic interferences but few anionic interferences.

Flameless Atomic Absorption Gas Chromatography

Abstract A flameless atom reservoir and an atomic absorption spectrophotometer have been used as A detector system for A gas liquid chromatograph. This flameless atomic absorption gas chromatograph permits high sensitivity element specific analysis for the volatile compounds of many elements including metals.

The determination of germanium by atomic absorption spectrometry with a graphite tube atomizer

A carbon filament atom reservoir and a graphite tube atomizer are compared as methods for the determination of germanium by atomic absorption spectrometry. It is shown that the filament technique is not applicable, probably because of loss of the sample as a volatile oxide species which results in inefficient atomization. The design of a small graphite tube atomizer is described; with this, a limit of detection for germanium of 3·10 -10 g was found. For a 20-μl sample, this corresponds to a concentration of 0.015 p.p.m. The interfering effect of 13 anions and cations is studied.

A comparative study of the determination of zinc and molybdenum by atomic absorption spectrometry with a carbon filament atom reservoir

A study is made of the operating parameters and interferences in the atomic absorption determination of an element which is readily atomized (zinc) and an element which is difficult to atomize (molybdenum) with a filament atom reservoir. This device seems better suited in real situations to the determination of involatile elements such as molybdenum and in this instance especially with a hydrogen/ nitrogen-sheathed gas. There were numerous interferences in the case of zinc, but only tungsten produced a significant effect in the determination of molybdenum.

Atomic absorption and fluorescence spectrometry with a carbon filament atom reservoir: Part XIV. The determination of vanadium in fuel oils

Atomic absorption and fluorescence spectrometry with a carbon filament atom reservoir: Part XIV. The determination of vanadium in fuel oils

Atomic absorption and fluorescence spectrometry with a carbon filament atom reservoir: Part XIII The determination of chromium with a fully enclosed atom reservoir

The detection and measurement of chromium by atomic absorption spectrometry with a carbon filament atom reservoir is described. At a wavelength of 357.9 nm, a sensitivity (1% absorption) of 9.2·10 -12 g was obtained. The detection limit was 1·1O -11 g; in terms of concentration this is similar to that normally detectable in a flame. Results are presented for the effects of a number of interfering species.