Spectroscopy in separated flames-II The use of the separated air-acetylene flame in long path atomic absorption spectroscopy

The application of a separated air-acetylene flame to the determination of several elements by long-path atomic-absorption spectroscopy is described. The factors which govern the stability and reproducibility of the separated flame have been investigated. High sensitivity and stability and low background absorption are obtained in the the determination of zinc, iron, copper, mercury, magnesium and silver by the method described.     

Spectroscopy in separated flames-III Use of the separated nitrous oxide-acetylene flame in thermal emission spectroscopy

The separation of a premixed nitrous oxide-acetylene flame at a modified commercial burner is described. The reducing interconal zone of the fuel-rich separated flame exhibits low radiative background. The reducing atmosphere and high temperature of this flame result in an effective medium for the excitation of the atomic line spectra of the refractory elements. The use of the fuel-rich flame in the flame photometry of these elements has been investigated.     

Spectroscopy in separated flames-IV: application of the nitrogen-separated air-acetylene flame in flame-emission and atomic-fluorescence spectroscopy

The primary and secondary combination zones of an air-acetylene flame have been separated by a stream of nitrogen flowing parallel to the flame to prevent access of atmospheric oxygen to its base. The flame is very stable over a wide range of fuel-air mixture strengths, and organic solvents may be aspirated without difficulty. The low flame background enables thermal-emission and atomic-fluorescence measurements to be made with high sensitivity. Bismuth, for example, has been determined in the range 5-200 ppm by its thermal emission at 306.8 nm, with a detection limit of 2 ppm in aqueous solution, and in the range 1-10 ppm with a detection limit of 0.3 ppm in 50% ethanolic solution. Zinc and cadmium have been determined at 213.9 nm and 228.8 nm by atomic-fluorescence spectroscopy in this flame with detection limits of 2 x 10(-4) ppm and 5 x 10(-4) ppm respectively, vapour-discharge lamps being used as sources of excitation. The results obtained represent a considerable improvement over those available by the same methods in a conventional air-acetylene flame.     

Spectroscopy in separated flames-V The argon- or nitrogen-sheathed nitrous oxide-acetylene flame in flame emission spectroscopy

The separation of the premixed nitrous oxide-acetylene flame by sheathing with argon or nitrogen is described. The interconal zone of the hot, slightly fuel-rich flame exhibits low background and noise levels and an extended reducing atmosphere, providing better conditions for the excitation of atoms of elements which form refractory oxides. The limits of detection found for nine such elements are greatly superior to those obtainable in the conventional unsheathed flame under similar conditions.     

The oxygen-shielded air-acetylene flame in emission analysis

Flame-emission studies have been made on 18 elements in the inner zone of an oxygen-shielded air-acetylene flame. The shielded flame gave higher emission sensitivity that that of the C(2)H(2)N(2)O flame for Cu and Tl, and comparable sensitivity for a number of other elements, but poorer sensitivity for elements forming stable refractory oxides in flames. The inner zone of the shielded flame has low emission-background and high flame-temperature, permitting good analytical sensitivity to be obtained with relatively low-resolution optical equipment.     

Spectroscopy in separated flames--VII: Determination of bismuth by atomic-fluorescence spectroscopy in a separated air-acetylene flame with electronically modulated electrodeless discharge tube sources

The application of electronically modulated and unmodulated bismuth and iodine electrodeless discharge lamps as sources for the excitation of bismuth atomic fluorescence in conventional and nitrogen-separated air-acetylene flames has been investigated. Separation of the flame results in improved detection limits for bismuth even when a modulated source is employed. The effect of 500-fold weight excesses of foreign ions on the determination of bismuth at 302.46 nm with a modulated iodine source and separated flame has been studied; only calcium and zirconium are found to cause significant interference. The determination of bismuth in aluminium alloy samples is reported.     

Application of an oxygen-shielded air-acetylene flame to atomic spectroscopy

A burner has been designed which provides an oxygen-shielded air-acetylene flame for atomic-absorption work. The chemical reducing properties of the oxygen-shielded flame operated under fuel-rich conditions are enhanced by the higher C: O ratio obtainable in the flame and by the higher flame temperature just above the reaction zone. The flame is inherently essentially free from the risk of flashback, and is offered as an alternative to the nitrous oxide-acetylene flame for use with certain types of equipment and for particular applications.     

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.     

Some optical studies with the air-acetylene flame

The application of Schlieren and shadow techniques for the study of flame processes is discussed in relation to analytically useful premixed flames. The information obtained, particularly with shadowgraphs, may be correlated with the measured signals and signal noise in atomic-absorption and flame-emission spectrometry.     

The use of multicomponent analysis in flame emission spectrometry

Summary Two-component analysis has been proposed for the determination of Na and K in HCl by flame emission spectrometry. The method is based on empirical mathematical models approximating the relationship between emission intensity and concentrations of sample components. The results obtained in the analysis of tens of samples of known composition show that the proposed method of determination is more reliable than others usually used.

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Anwendung der Multikomponenten-Analyse in der Flammenemissions-SpektrometrieBestimmung von Na und K in Salzsäure

Zusammenfassung Zur Bestimmung von Na und K in Salzsäure durch Flammenphotometrie wird eine Methode der Zweikomponentenanalyse vorgeschlagen, die auf empirischen mathematischen Modellen beruht, die der Beziehung zwischen Emissionsintensität und Elementkozentration angenähert sind. Ergebnisse von zahlreichen Analysen bekannter Proben beweisen, daß die beschriebene Methode zuverlässiger ist als bisher benutzte andere Verfahren.

     

The use of sample additives in flame emission spectrometry

New kinds of sample additives were investigated to increase the efficiencies of desolvation and atomization in flame spectrometry. Hydrazine and nigrosin were chosen as chemical and dye additives, respectively; an enhancement in the flame-emission signal was obtained in both cases. With nigrosin, it was possible to eliminate completely the interference of phosphate on a calcium emission signal. The increase in the signal for both additives was believed initially to be due to the more rapid evaporation of droplets in the sample aerosol. Further evidence, however, suggested that enhanced vaporization is responsible for the observed signal increase. It is suggested that similar sample additives might be useful also in inductively-coupled plasma emission spectrometry.     

Contribution to the atomic absorption spectrophotometry of magnesium in the air-acetylene flame

Summary Non-sufficient attention seems to have been paid to the influence of various ions on the atomic absorption spectrophotometric determination of magnesium. SiO₃ ²⁺, Al³⁺, Be²⁺, Zr(IV), Ti(IV) decrease remarkably the Mg absorbance in air-acetylene flames, but the most interesting positive or negative effects on the absorbance of magnesium are exhibited in ternary systems of ions. 5-Sulphosalicylic acid protects magnesium in the presence of the above mentioned elements in binary or ternary ion systems and makes the atomic absorption spectrophotometric determination of magnesium possible in the presence of these ions.

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Zur atomabsorptionsspektrophotometrischen Bestimmung von Magnesium in der Luft-Acetylen-Flamme

Zusammenfassung Den verschiedenen Beeinflussungen durch Kationen und Anionen bei der atomabsorptionsspektrophotometrischen Bestimmung von Magnesium wurde bisher nur unzureichende Aufmerksamkeit gewidmet. Vor allem SiO₃ ^2–, Al³⁺, Be²⁺, Zr(IV), Ti(IV) üben einen merklichen negativen Einfluß auf die Absorption von Magnesium in der Acetylen-Luft-Flamme aus. Von besonderer Bedeutung sind verstärkte negative bzw. positive Einflüsse in ternären Ionensystemen, die die Resultate stark beeinträchtigen können. 5-Sulfosalicylsäure eignet sich im allgemeinen gut zur Aufhebung des störenden Ioneneinflusses bei der Bestimmung von Magnesium neben den oben genannten Elementen in binären oder ternären Systemen in Acetylen-Luft-Flammen.

     

Atomic and molecular absorption spectra of indium in air-acetylene flame

Absorption spectra of both atomic and molecular species in the air-acetylene flame, which are produced when the aqueous solutions of indium dissolved in HNO₃, HF, HCl, HBr and HI were aspirated into the flame, have been investigated in the u.v. region. Numerous atomic absorption lines of indium have been observed in the absorption spectra. Most of these lines were previously listed only as emission lines. Those atomic lines have been ascribed to the electronic transitions from the ground states of 5p ²P_1/2⁰ and 5p ²P_3/2⁰ to the excited states such as ls ²S_1/2, md ²D_3/2, nd ²D_5/2, 4p^{2 4}P_1/2, 4p^{2 4}P_3/2 and 4p^{2 4}P_5/2, respectively, where 13 l 6 and 14 m,n 5. The molecular absorption bands for InF, InCl and InBr in the airacetylene flame have been also observed near 234 nm, 267 nm and 282 nm, respectively, as the electronic transition of ¹Σ⁺ → ¹Π₁ Those absorption bands show fine structures due to the molecular vibrations. The spectral parameters for the molecular vibrations have been obtained from the simulations of the observed spectra. The molecular absorption band for InI was not observed because of the decomposition of the molecule in the flame. In addition, the molecular absorption band for InO has been observed near 273 nm and those for NO near 205 and 215 nm.     

Some observations on relative atomization efficiencies in the air-acetylene flame as a function of flame temperature

An experimental study of the variation of the degree of atomization due to significant cooling of the air-acetylene flame was made with the help of plots ofabsorbance ratios against flame temperature. A heated spray chamber without water-cooled condenser was used to introduce a large amount of the solution into the flame. The effect of temperature lowering on the degree of atomization was found to be larger the higher the value of the dissociation energy of the molecule that may be formed in the flame. The order of change in relative atomization efficiency for various metals with decreasing flame temperature is Mo > Cr > Pb > Sb > Ni, Fe, Co > Mn > Cd, Zn > Ag.     

Atomic-fluorescence characteristics and analytical determination of manganese in an air-acetylene flame

The atomic-fluorescence characteristics of manganese atoms in a premixed nitrogen-shielded air-acetylene flame are described. Excitation is obtained at 280 nm from a microwave-excited electrodeless discharge tube. A detection limit of 0-001 ppm for the determination of manganese by atomic-fluorescence spectroscopy is obtained by measurement of the resonance fluorescence observed at this wavelength. In addition to several other weaker atomic-fluorescence signals observed from manganese atoms in the flame, weak resonance fluorescence at 258 and 260 nm from manganese ions stimulated by ion line-emission from the source has been recorded. Linear calibration graphs for atomic-fluorescence measurement at 280 nm are obtained over the range 0.0025-10 ppm of manganese in aqueous solution. Of 26 foreign anions and cations examined for interference at the 1000-fold weight excess level only four produced interference. Large amounts of Si, Th and V interfere by scattering of the incident radiation, while Mg causes depression of the atomic fluorescence by a chemical effect.     

Atomic-absorption determination of copper impurities in zirconium salts using an air-acetylene flame

Summary An AAS method is described for the direct determination of traces of copper in zirconium(IV) oxide chloride and nitrate. An interference study of the zirconium matrix is reported. Best conditions for the removal of the suppressive effect of zirconium on the copper signal by addition of hydrofluoric acid are described. Results obtained by analyzing commercial samples from different manufacturers are presented.The author thanks Prof. P. Lanza for helpful discussions.     

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.