The determination of aluminum and beryllium by atomic absorption spectroscopy

The use of atomic absorption spectroscopy for the determination of aluminum and beryllium has been studied. The nitrous oxide-acetylene flame was found to be useful for the determination of trace amounts of either aluminum or beryllium. Beryllium can also be determined in an oxy-acetylene flame at the 1 p.p.m. level and upwards if the aqueous solution contains 10% of diethylene glycol diethyl ether. The determinations were essentially free from interferences.     

Atomic-fluorescence spectroscopy of magnesium with a high-intensity hollow-cathode lamp as line source

Atomic fluorescence of magnesium is possible in air-propane or air-acetylene flames at 285.21 nm, using a high-intensity hollow-cathode magnesium lamp for excitation. The technique permits determinations of magnesium in the range 0.01–5 p.p.m., i.e. with more than 10 times the sensitivity of the atomic absorption method even for this most sensitive element. The detection limit in either flame is 1 ng/ml (signal: noise ratio 1 : 0.75). In a nitrous oxide-acetylene flame, atomic fluorescence may be carried out with linear signal/concentration dependence up to 100 p.p.m. without interference even from metals such as aluminium, titanium, etc. at a 1000-fold excess ratio to magnesium. A brief comparison is made with atomic absorption using the same source and equipment.     

The determination of gallium by atomic absorption spectrometry

The use of a nitrous oxide-acetylene flame for the determination of gallium by atomic absorption spectrometry was compared with the use of air-acetylene flames. The nitrous oxide method provided higher sensitivity and was much less sensitive to acid and base composition and to diverse added salts. Significant matrix and background effects, which occurred when gallium was determined in ore solutions with the air-acetylene flame, were eliminated with the nitrous oxideacetylene flame.     

Dissociation and ionization effects in atomic absorption spectrochemical analysis

Use of a nitrous oxide-acetylene flame in atomic absorption spectrophotometry reduces or eliminates certain chemical interferences that have been observed in cooler flames. However, ionization increases with temperature, and is significant for some elements in the nitrous oxide-acetylene flame. Ionization can be reduced by adding an easily ionized metal (e.g. alkali metal) to the solution. Elements likely to be determined using the nitrous oxide-acetylene flame which will be significantly ionized are: Al, Ba, Ti, V, Zr, Hf, Nb, Sc, Y, the lanthanides and the actinides. The ionization of an element in the nitrous oxide-acetylene flame can be readily calculated by taking absorption readings, provided that relatively sensitive atom and ion resonance lines are available. This technique possibly could be used to establish ionization potentials or partition functions of those lanthanide elements that are not now well known.     

The determination of rubidium and caesium in geological materials by atomic emission spectrophotometry with a nitrous oxide-acetylene flame

An atomic emission spectrophotometric procedure is presented for the determination of rubidium and caesium at the per cent and p.p.m. levels. A nitrous oxide-acetylene flame and a potassium ionization buffer are used. There is no need for prior separation, pre-concentration or general matrix matching of standards.     

Effect of mixed organic solvents on atomic absorption spectrophotometry of refractory metals

The effect of various organic solvents on the absorption characteristics of vanadium was studied in fuel-rich oxy-acetylene and nitrous oxide-acetylene flames. The absorption of the 3183.9 Å line of vanadium was greatly enhanced by the use of various mixed organic solvents when fed to oxy-acetylene flames. In the case of the nitrous oxide-acetylene flame, the addition of diethylene glycol (about 8% in the final solution) and similar compounds to the aqueous solution of vanadium increased the absorption by about 50%. The observations and the possible role of the mixed organic solvents are discussed.     

The determination of beryllium in geological and industrial materials by atomic-absorption spectrometry after cation-exchange separation

A method is described for the determination of beryllium in geological and industrial samples. After dissolution of the sample in mineral acids, beryllium is separated from the matrix elements by chloroform extraction of its acetylacetonate from a solution of pH 7 containing ascorbic acid and EDTA. Beryllium is separated from the organic extract and from co-extracted aluminium by means of a column of the strongly acidic cation-exchanger Dowex 50; beryllium is adsorbed from a medium consisting of 60 % (v/v) tetrahydrofuran, 30 % (v/v) chloroform and 10 % (v/v) methanol containing hydrochloric acid, aluminium is removed with 0.4 M oxalic acid and after elution with 6 M hydrochloric acid, beryllium is determined by atomic-absorption spectrometry with a nitrous oxide-acetylene flame. The method was used to determine p.p.m. and sub-p.p.m. quantities of beryllium in geochemical reference materials, U₃O₃ and yellow cake samples, and manganese nodules.     

The application of a piezoelectric scanning Fabry-Perot Interferometer to the study of atomic line sources—III: Use of the channeled spectra produced with a continuum source for studies of the absorption line-width for calcium atoms in flames

An instrumental arrangement has been developed for the interferometric study of the half-width of atomic lines in absorption using a spectral continuum source. The variation of observed half-width of the calcium absorption line at 422·67 nm with calcium concentration has been examined in air-acetylene and nitrous oxide-acetylene flames supported as cylindrical flames with and without flame shielding and at long path burners. Extrapolation of the curves obtained to zero added calcium concentration in the flame may allow for correction for self-absorption and flame characteristics and calculation of collisional broadening half-widths and damping constants (a-parameters).     

Determination of vanadium by atomic absorption spectrophotometry

Methods for the determination of vanadium, in the range 0.5–100 mg/l, by atomic absorption spectroscopy in an oxy-acetylene as well as in a nitrous oxideacetylene flame are presented. For use with oxy-acetylene flames, vanadium is extracted as vanadium cupferrate into a mixture of methyl isobutyl ketone and oleic acid (78:22, v/v) and the organic phase is aspirated to the flame. The sensitivity is 0.7 mg/l of vanadium in the organic phase. For nitrous oxide-acetylene flames, an aqueous solution of vanadium is aspirated directly. The sensitivity is further improved by the use of methyl isobutyl ketone, the addition of Al³⁺ and diethylene glycol diethyl ether. Many potential interferences were examined and methods to overcome those found are given.     

Studies in atomic fluorescence spectrometry: Part II. Interference effects in the determination of tin with various premixed flames

The interference effects are reported for 27 elements, 6 acids and 4 organic liquids on the atomic fluorescence determination of tin with argon-hydrogen, argon-oxygen-hydrogen and argon-separated air-acetylene flames. The addition of1000 p.p.m. iron (III) eliminates most interferences from the elements but not from the acids. The basic trends in the interference effects in the argon-hydrogen flame for the atomic absorption and atomic fluorescence determinations of tin are similar. The detection limit, for an 18.2-s time constant, in the argon-oxygen-hydrogen and argon-hydrogen flames is 0.006 p.p.m. and in the air-acetylene flame it is 0.05 p.p.m. These detection limits are significantly better than previously reported limits. Analytical curves in all three flames studied are linear between the detection limits and 250 p.p.m.     

The significance of the CrO(4)2- chemical equilibrium HCr(4)- equilibrium in the determination of chromium(VI) by flame spectrometry

Chromium atomic absorption for Cr(VI) solutions in the air-acetylene and air-hydrogen flames is pH-dependent, but not in the nitrous oxide-acetylene flame. The effect is shown to occur as a result of the HCrO(-)(4) chemical equilibrium CrO(2-)(4) equilibrium, and may cause significant errors in the determination of chromium by atomic-absorption Spectrometry unless the pH of sample and standard solutions is controlled.     

Laser excited atomic fluorescence of some transition elements in the nitrons oxide-acetylene flame

A pulsed, tunable dye laser, pumped with a nitrogen laser is used to excite the atomic fluorescence of Sc, V, Hf, Nb, Os, Zr, W, Rh and Ru. Except in the case of Rh, the nitrous oxide-acetylene flame has been used. The results obtained for Zr and W are due to scattering of the laser radiation from unvaporized particles in the flame. Since, for most elements, several fluorescence lines of comparable intensity have been observed after the primary excitation process, the usefulness of observing non-resonance fluorescence is stressed, particularly with regard to the possibility of minimizing spectral interferences. The experimental results demonstrate that the limits of detection obtained with the dye laser source are comparable or better than the best atomic absorption limits only when the same primary absorption line used for the atomic absorption measurements can be used for exciting the fluorescence.     

The application of a piezoelectric scanning Fabry-Perot interferometer to the study of atomic line sources—II: Line-widths for calcium in air-acetylene and nitrous oxide-acetylene flames

The variation in observed half-width of the calcium 422.7 nm line with calcium concentration has been studied interferometrically in air-acetylene and nitrous oxide-acetylene flames supported as cylindrical flames, with and without flame shielding and inert gas separation, and at a long path burner. Extrapolation of the curves obtained to zero added calcium concentration is shown to permit correction for self-absorption and calculation of interaction broadening half-width and damping constants (a-parameters).     

Some analytical properties of low pressure flames

An investigation has been made into the analytical behaviour of low pressure nitrous oxide-acetylene and oxy-acetylene names, between pressures of ca. 15–300 and 10–100 torr, respectively, for the purposes of atomic emission spectroscopy. Samples were introduced into the flame on a loop of tungsten wire, and the resulting emission pulses measured in the space immediately beyond the edge of the primary reaction zone. Attention was largely concentrated on metals which are difficult to determine in conventional atmospheric flames. Absolute detection limits for Sr, Al, Cr, Cu, Ti and V lie in the range 10⁻⁹–10⁻¹⁰ g. The relative atomisation efficiences of the flames used were also measured, and were found to increase with decreasing pressure; an effect attributed to the highly reducing properties of a low pressure flame, and one which was felt to account for the high analytical sensitivity obtained in these studies.     

An experimental and theoretical evaluation of the nitrous oxide-acetylene flame as an atomization cell for flame spectroscopy

The formation of free atoms from aerosols of metal-containing solutions introduced into nitrous oxide-acetylene flames is examined by: (a) inference from well identified reactions and equilibria prevailing in cooler flames; (b) calculations employing a thermodynamic flame model; and (c) experimental observation of relative free-atom number densities in the flames as a function of stoichiometry. The calculated partial pressures of the major natural flame species and some of the spectroscopically observed minor species are presented as a function of the flow ratio of nitrous oxide to acetylene (p). Predicted relative number densities of Na, Mg, Cu, Fe, Li, Be, Al, W, Ti and Si as a function of p are compared with measured free-atom absorbances in an argon-shielded flame. These comparisons were completed for various heights above the burner tip. The data reported show that: (a) the degree of metal atomization in the nitrous oxide-acetylene flame can be adequately described by the equilibrium state; (b) in general, when solute vaporization is complete, there exists a value of ρ at which atomization is complete for metals that form monoxides with dissociation energies less than ~ 6.5 eV; and (c) certain metals may form carbon-containing compounds in the interconal zone.     

Study on the elimination of interferences in the determination of strontium by atomic absorption spectrophotometry

Summary Recommended operating conditions for the determination of strontium by atomic absorption spectrophotometry are given for both the air-acetylene and nitrous oxide-acetylene flames. Details are given of interference effects which can occur in the air-acetylene flame and also of a method to eliminate these effects using lanthanum as a releasing agent. In the nitrous oxide-acetylene flame no interference effects occurred if all solutions measured contained an ionisation buffer.

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Untersuchung zur Ausschaltung von Störungen bei der Bestimmung von Strontium durch Atomabsorptionsspektralphotometrie

Zusammenfassung Arbeitsbedingungen werden für die Luft-Acetylen- und die N₂O-Acetylen-Flamme gegeben. Die Störungen, die in der Luft-Acetylen-Flamme auftreten, werden im einzelnen besprochen und ihre Ausschaltung durch Lanthanzusatz beschrieben. In der N₂O-Acetylen-Flamme treten keine Störungen auf, wenn die Lösungen einen Ionisierungspuffer enthalten.

     

spectroscopy in separated flames-VI The argon or nitrogen-sheathed nitrous oxide-acetylene flame in atomic-absorption spectroscopy

The separation of the premixed nitrous oxide-acetylene flame at a 50-mm slot burner by sheathing with argon or nitrogen is described. In comparison with the conventional flame, the interconal zone of the hot, slightly fuel-rich separated flames provides better conditions for the maintenance of free atoms of elements which form refractory oxides. Optimum conditions for the determination by atomic-absorption spectroscopy of the elements Al, Be, Ge, Mo, Si, Ti, V and Zr in both separated and conventional flames at the same burner have been established. Significant improvement in detection limits and sensitivities is obtained in the separated flames.     

Determination of strontium in human tooth enamel by atomic absorption spectrometry

Interferences in the atomic absorption of strontium by calcium and phosphate at the levels found in human tooth enamel were investigated for both air-acetylene and nitrous oxide-acetylene flames. In air-acetylene flames, the interferences can be reduced by the addition of lanthanum(III); but perchloric acid, used for sample dissolution, causes a significant reduction in the calcium-phosphate interference, so that a standard addition method can be applied, without the need for any chemical separations. An average recovery of 98.6% for added amounts of strontium to enamel showed the proposed method to be reliable.     

Comparative study for aluminum determination in bone by atomic absorption techniques and inductively coupled plasma atomic emission spectroscopy

A comparative investigation was carried out on the suitability of atomic absorption spectrometry and inductively coupled plasma atomic emission spectroscopy for aluminum determination in bone. Both techniques give reliable results but the nitrous oxide-acetylene flame method was not found to be sensitive enough to accurately measure low aluminum content. A suitable method for sample treatment is also described. Quantitation of aluminum in bone from patients on regular hemodialysis is also done.     

A study of some matrix effects in the determination of beryllium by atomic-absorption spectroscopy in the nitrous oxide-acetylene flame

A study has been made of a number of interferences observed in the trace determination of beryllium by atomic-absorption in the nitrous oxide-acetylene flame. The major negative interference caused by the presence of excess of aluminium salts may be overcome by the use of 8-hydroxyquinoline. Magnesium and silicon also depress the Be signal, but most other metals cause enhancement. In most instances the enhancements may be made uniform by the addition of potassium ions to the sample solution.