Nitrous Oxide-acetylene Flame Research Articles

Flame atomic emission spectrometric determination of aluminium in a bovine blood plasma matrix

A flame atomic emission spectrometric method, is described for the determination of aluminium in bovine blood plasma matrices. Plasma samples are wet-digested and solutions are aspirated into a conventional nitrous oxide-acetylene flame. Analyte emission is monitored at 396.15 nm with corrections for background emission being obtained from measurements several tenths nm on both sides of the aluminium line. The mean recovery of 0.3–5 μg/ml aluminium added to model solutions containing 500–5000 μg Na/ml, 50–1000 μg Ca/ml, 2000–5000 μg K/ml, or simulated plasma digests containing Na, K, and Ca was 100,6% (SD = 10.9, df = 60); the mean recovery of 0.3, 0.5, and 1.0 μg/ml aluminium added to blood plasma before digestion was 94.3% (SD = 9.8, df = 33) indicating no serious interferences. For standard solutions, the detection limit (signal: peak-to-peak noise = 1) was 0.02 μg/ml by flame emission, and 0.12 μg/ml by atomic absorption measurements with the same instrument. A sample taken through the analytical procedure, gave a detection limit of 0.05 μg/ml suggesting the submicrogram per milliliter region as the lower practical limit of the method.

Atomization of molybdenum in air-acetylene and nitrous oxide-acetylene flames

The effects of flame stoichiometry, nature of the metal complex or compound, and the solvent on the atomic absorption signal of molybdenum have been investigated. Spatial distributions (profiles) of molybdenum free-atom populations are presented. These profiles were obtained by using various molybdenum compounds or complexes dissolved in aqueous or organic solvents and nebulizing them into unshielded, air-acetylene and nitrous oxide-acetylene flames of various stoichiometries. The highest free-atom population density (maximum absorbance) was localized in a rather small area of the flame and was obtained only in a highly reducing nitrous oxide-acetylene flame by using organomolybdenum compounds. However, the chemical nature of the organometallic compounds is also important in determining the sensitivity. Equally important was the particular compound or complex-solvent combination employed. This latter aspect was expressed in terms of specific ''enrichment factors'' for the compound or complex-solvent systems studied. (auth)

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.

Determination of trace amounts of tin in geological materials by atomic absorption spectrometry

An atomic absorption method is described for the determination of traces of tin in rocks, soils, and stream sediments. A dried mixture of the sample and ammonium iodide is heated to volatilize tin tetraiodide -which is then dissolved in 5 % hydrochloric acid, extracted into TOPO-MIBK, and aspirated into a nitrous oxide-acetylene flame. The limit of determination is 2 p.p.m. tin and the relative standard deviation ranges from 2 to 14 %. Up to 20 % iron and 1000 p.p.m. Cu, Pb, Zn, Mn, Hg, Mo, V, or W in the sample do not interfere. As many as 50 samples can be easily analyzed per man-day.

The significance of the CrO 2−4 ⇌ HCrO −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 ⇌ 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.

Molecular fluorescence spectroscopy of phosphorus monoxide in flames studied by a SIT-OMA system

Molecular fluorescence of PO produced in flames and excited by an Eimac xenon arc continuum source has been investigated. An SIT image detector combined with an optical multichannel analyzer (OMA) was used as the detector. Molecular fluorescence of PO could be observed near 246 nm in the air—acetylene, air—hydrogen, oxygen/argon—hydrogen, and the corresponding argon-separated flames, while PO fluorescence enhanced by molecular emission was observed in the nitrous oxide—acetylene flame and in the argon-separated nitrous oxide—acetylene flame. The fluorescence spectrum of PO near 246 nm is identical to the emission and absorption spectra of PO and is ascribed to the γ system, which is caused by the electronic transition A 2Σ- X 2Π. PO emission observed near 324 nm, a result of the transition D 2Σ X 2Π, was very weak in the present experiment and was not accompanied by measurable quantities of fluorescence. The fluorescence intensity of PO depends primarily upon the flame temperature, and so the quenching effect of nitrogen on the fluorescence intensity could not be observed. The best detection limit for phosphorus was obtained in the argon separated air—hydrogen flame, which generated the least amount of flame background noise, and was about 80 μg P/ml. Finally, because phosphine (PH 3) is an impurity in commercial acetylene, PO fluorescence bands in the 230–270 nm region may obscure the atomic fluorescence signals in this region excited via continuum sources and thus deleteriously affect atomic fluorescence signals in certain analyses.

Absolute analysis by flame atomic absorption spectroscopy: Present status and some problems

Recent progress and main problems encountered in the theoretical interpretation of some stages in the spectrochemical analysis by flame AAS with a slot burner and a sharp-line source are reviewed. The effect of “narrowing” of the aerosol stream as compared with the gas stream above the flame front was established theoretically and confirmed experimentally. The resulting theory describing the analyte distribution across the flame permitted to explain many features of these flames, in particular, the effect of sensitivity enhancement in the presence of an excess of matrix. A simple method is proposed for the determination of atomic diffusion coefficients. The results of calculations of the composition and temperatures of flames employed in analytical practice, obtained for a wide range of the fuel—oxidant ratio, were used to determine the capabilities of these flames as to the dissociation of monoxides. Practically total dissociation of almost all elements of the Periodic Table was proved theoretically and confirmed experimentally to occur in the nitrous oxide—acetylene flame. The formation of low-volatile lithium and tin carbides in the presence of carbon was established. This effect accounts for “anomalies” in the behavior of these elements in low-temperature flames. The line shifts Δν s in flames were measured by interferometric scans of line profiles from a hollow-cathode lamp and flame. The existence of a theoretical relationship between Δν s and the Lorentz line width Δν L was confirmed. Calculations of line absorption were generalized to take into account the shift and hyperfine structure of the lines. Systematic errors in these calculations do not exceed 10%. A discussion is given of the major difficulties facing absolute measurements based on this analytical technique.

The determination of chromium in plain carbon steel and low-alloy iron and steel by atomic-absorption spectrophotometry

Co-operative examination of published atomic-absorption procedures for several elements in steel showed good agreement between results apart from those for chromium. For this element the depressive effect of iron in the air-acetylene flame is eliminated when using the preferred nitrous oxide-acetylene flame. However, control of flame composition is essential as vanadium, molybdenum, aluminium and titanium in low-alloy synthetic test solutions and samples increasingly enhance the chromium absorbance with increased fuel richness. Copper, nickel and iron have no effect but, in any event, iron should be included in the calibration solutions. Hence a lean, oxidising flame must be used and the results for samples then agree closely with the certificate values.

Spectral source profiling with a photodiode array

A computer controlled Reticon photodiode array was used for source profiling by juxtapositioning the detector with the exit slit of a stigmatic monochromator, with the long axis of the array parallel to the slit. The sources to be studied were imaged on the monochromator entrance slit and the individual elements of the array detected light of a specific wavelength emitted from a different portion of the source as it appeared at the exit slit. The 512 array elements covered 12.5 mm of slit length. Larger or smaller portions of the source may be studied depending on the optics used to form the image on the entrance slit. Vertical profiles required only simple lenses for imaging. Profiles in horizontal direction were made quite simply by placing a Dove prism in the optical path to rotate the image 90°. Use of the system for elemental emission profiles for the nitrous oxide-acetylene flame and inductively coupled plasma is reported.

The Application of Molecular-flame-absorption Spectroscopy to the Elucidation of Chemical Interferences in Indium Atomic Absorption Spectrometry

Abstract The atomic absorption spectrometry of indium was investigated in air-acetylene and nitrous oxide-acetylene flames. The atomic absorptions of indium were significantly interfered by HCl, HClO4, and HBr in both the flames. The chemical interferences can be explained by the formation of diatomic molecules, such as InCl and InBr, the molecular absorption spectra of which were really observed in flames.

Use of a nitrous oxide-acetylene flame to minimize interferences in microsampling-cup atomic absorption spectrometry

Use of a nitrous oxide-acetylene flame to minimize interferences in microsampling-cup atomic absorption spectrometry

ChemInform Abstract: PROFILES OF THE DISTRIBUTION OF ATOMS IN THE NITROUS OXIDE‐ACETYLENE FLAME

AbstractDie Verteilung der neutralen Atome von 16 Elementen in der NzO‐Acetylen‐Flamme wird nach Einsprühen ihrer Hydrat‐Ionen in die Flamme durch Extinktionsmessungen ermittelt.

Use of a microsampling cup system with a nitrous oxide-acetylene flame for determining less volatile metals

Use of a microsampling cup system with a nitrous oxide-acetylene flame for determining less volatile metals

Profiles of the Distribution of Atoms in the Nitrous Oxide–acetylene Flame

Abstract The distributions of neutral atoms in the nitrous oxide–acetylene flame have been measured by nebulizing aquo ions of the following sixteen elements into the flame; cadmium, nickel, zinc, copper, lead, cobalt, manganese, iron, chromium, molybdenum, calcium, tin, gallium, indium, titanium, and boron. The distributions have been figured on the response surfaces on which the changes in distribution are expressed as functions of the flame height and the acetylene flow rate. The response surfaces for the temperature and the OH radical were also investigated. The response surfaces for the atomic absorptions of the elements can be related to the thermodynamic properties of the oxides of the elements. The results have then been used for the discussion of the atomization processes of the elements in the flame. In addition, the sensitivities of absorption spectrometry in the nitrous oxide–acetylene flame have been compared to those in the air–acetylene flame.

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.

Some observations on the interdependence of cyanide concentration and atomization efficiency in the nitrous oxide-acetylene flame

A relationship is derived between CN concentration and atomization efficiency in the C 2H 2-N 2O flame. The relationship is examined under various experimental conditions and β values are estimated for a number of elements. The possibility of complex vapour phase oxide formation by U is considered.

Atomic-absorption determination of strontium in silicate rocks: a study of major element interferences in the nitrous oxide-acetylene flame

A study has been made of the major element interferences associated with the atomic-absorption determination of trace amounts of strontium in silicate rocks by using a nitrous oxide-acetylene flame. Aluminium causes suppression of the strontium signal, while calcium and magnesium act as partial releasing agents, thus reducing the effect of the aluminium. Exact matching of samples and standards can be avoided by the use of lanthanum, which has been shown to be an effective releasing agent in the nitrous oxide-acetylene flame.

Eine methode zur bestimmung von fluorkonzentrationen mit hilfe der atomaren absorption

An analytical method for the specific determination of fluorine by atomic absorption spectrometry (AAS) has been developed. The sample is mixed with excess SiO 2 and H 2SO 4 and heated to promote the formation of SiF 4. The gas is fed to an atomization cell, where the atomic concentration of Si is measured by AAS using the resonance line at 251,6 nm, the Si concentration being a measure for the fluorine concentration in the original sample. The authors inuestigated both an acetylene-nitrous oxide flame and a graphite furnace as atomization cells. Relative standard deviations of 6–7% (furnace) and 8.8% (flame) and detection limits of 0.17 μg F (furnace) and 30 μg F (flame) were found. Recoveries in known samples were established to be between 89 and 94 %.

Determination of Trace Amount of Vanadium in Air by Flameless Atomic Absorption Spectrophotometry

A method for determination of vanadium in air by flameless atomic absorption spectrophotometry was studied. Atomospheric particulates were collected on a Gelman filter by a high-volume air sampler, and extracted with 5% hydrochloric acid. Cupferron, a chelating agent, reacts with vanadium to form a complex, which can be extracted with methyl isobutyl ketone. The solvent was dried, ashed, and atomized by passing through a high electric current of the atomizer. The concentration of vanadium was calculated directly from the calibration curve by measuring the absorbance of vanadium at 318.5 nm. Cations, except tin, did not interfere the determination of vanadium seriously. Analytical results were in good agreement with those obtained by a nitrous oxide-acetylene flame atomic absorption spectrophotometry. The coefficient of variation was from 4.4% to 9.4%, and the limit of detection was 0.03 ppm of vanadium, when the signal/noise ratio was 2.

Atomic-emission spectrometry with an induction-coupled high-frequency plasma source Comparison with the inert-gas shielded premixed nitrous oxide-acetylene flame for multi-element analysis

The performance for trace analysis in solution by atomic-emission spectrometry from a 36-MHz induction-coupled radiofrequency plasma atom-cell is predicted from a simple model and compared with the corresponding characteristics of an inert-gas shielded nitrous oxide-acetylene flame. A longer linear calibration range is predicted for the plasma source owing to the greater freedom from self-absorption under optimum operating conditions, and the long residence time of analyte species confers freedom from solute vaporization interferences. The predictions are verified experimentally and the advantages of the use of the plasma source are demonstrated in the analysis of aluminium alloys for copper, iron, magnesium, manganese, titanium and zinc.