Solvent extraction—flame spectrometric methods for the determination of indium in aluminium alloys

Atomic absorption and atomic emission methods for determining trace and minor amounts of indium in aluminium alloys are described. They involve the separation of indium from the aluminium matrix by extraction of indium diethyldithiocarbamate from hydrochloric acid at pH 3, and determination by emission at 451.13 nm or absorption at 303.9 nm in the extract; a nitrous oxide—acetylene or air—acetylene flame is used.     

Condensed phases in flame spectrometry: an equilibrium model of the acetylene flame

An equilibrium model for a wet acetylene flame has been used for the calculation of the distribution of carbon, aluminium and silicon between gaseous and condensed phases. Calculated values of free atom vapour fractions are in agreement with published experimental data. It is thermodynamically probable that the formation of condensed phases limits atom vapour formation. There is a relationship between the position of an element in the Periodic Table and the nature of the condensed phase.     

Analysis of yttrium aluminium borate crystals by solution-based methods: inductively coupled plasma atomic emission spectrometry and flame atomic absorption spectrometry

Comparative analysis of yttrium aluminium borate (YAB) /YAl₃(BO₃)₄/ optical single crystals was performed by flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) methods for Cr, Dy, Er, Yb, Y, Al, B and Mo. The dopant element, Ce, could be determined only by the ICP-AES method at the required concentration level. The powdered crystal samples were fused with lithium metaborate (LiBO₂) at 950 °C in a platinum crucible and then dissolved in 6 mol l⁻¹ HCl. Although this fusion-dissolution procedure proved to be simple and effective, the quantitative determination of B—as the matrix element in samples—was handicapped by the B content of the fusing reagent. For the FAAS method, with the use of nitrous oxide–acetylene flame, cesium chloride ionization buffer and lanthanum chloride releasing agent [0.1+0.2% (m/v), respectively] were applied. These agents enhanced the atomic absorption signals of Cr, Dy, Er, Mo, Yb and Y, whereas no change of sensitivity was resulted in for Al and B. A fairly good agreement was found between the results of the two alternative spectrochemical methods. The predicted stoichiometry of the crystals was also well approximated indicating the reliability of the crystal growth technology applied.     

The photodissociation of alkali halides in air—acetylene flame as studied by molecular absorption spectroscopy

Absorption spectra of alkali salts, which were aspirated into the air—acetylene flame, have been investigated in the u.v. and visible region, where a conventional atomic absorption spectrometer with an analog data processing system was used for obtaining the spectra. Molecular bands which arose from the alkali halides and oxides were observed along with atomic lines. In the case of lithium, only molecular absorption bands of lithium oxide were observed in the flame, even when lithium halides were aspirated. These molecular absorption bands can be interpreted in terms of photodissociation processes of the alkali halides and oxides produced in the flame.     

The role of various flame constituents in the production of atoms in the air—acetylene flame

Atom-formation processes in the premixed air—acetylene flame used in atomic absorption spectrometry are examined. Flame profiles of copper, indium and calcium atoms for five flames of differing acetylene: air ratios are compared with the flame profiles of temperature and the natural flame species C₂, CH and H. The flame profiles of the metals bear little resemblance to the temperature profile. C₂ and CH radicals are shown to be confined to the lower region of the flame (approximately to the region of the reaction zone), whereas H radicals persist far beyond the reaction zone. The strong resemblance of the profile of indium atoms to that of H radicals suggests the participation of H radicals in indium atom formation. Experiments on the action of the flame on solid calcium oxide similarly suggest the involvement of H radicals in the reduction of calcium oxide.     

Synthetic hydromagnesite as flame retardant. Evaluation of the flame behaviour in a polyethylene matrix

Synthetic hydromagnesite obtained from an industrial by-product was evaluated as a non-halogenated flame retardant. It was used in combination with aluminium hydroxide (ATH) and compared with commercial flame retardants like magnesium hydroxide (MH) and natural hydromagnesite-huntite (U) in a polyolefin system of low-density polyethylene/poly(ethylene-co-vinyl acetate) (LDPE/EVA).The thermal stability and flame behaviour of the halogen free flame retarded composites were studied by thermogravimetric and differential thermal analysis (TG-DTA), limiting oxygen index (LOI), epiradiateur and cone calorimeter. It has been shown that synthetic hydromagnesite could be an alternative solution to the use of MH in non-halogenated flame retardant systems in EVA.     

Application of experimental design for investigating the determination of titanium in glass ceramics by flame atomic absorption spectrometry

Interferences of the matrix elements of glass ceramics (Al, Mg, Na and Si) on the titanium signal obtained by atomic absorption spectrometry with a nitrous oxide/acetylene flame were studied by means of experimental design. Quadratic polynomials were chosen as the model; full factorial designs with two, three and four variables at three levels were applied. As expected, aluminium increased the titanium signal, while magnesium reduced it. All the investigated elements interfered nonadditively with the titanium signal; the standard addition method therefore does not provide accurate results. Graphic evaluation of the empirical response surfaces was used to establish optimum conditions for titanium; these surfaces were compared with the polynomial surfaces to check the models. The results obtained on interactions in the system are used with some thermodynamic data to estimate the nature of the compounds formed in the flame. The strong interferences on the titanium signal requires fairly close matrix matching between the standard and sample solutions. The proposed method allows the determination of 3–6% Ti in glass ceramics with a relative standard deviation of 1%.     

The determination of selenium by atom-trapping atomic absorption spectrometry

The application of atom-trapping atomic absorption spectrometry to the determination of selenium has been studied in detail. The optimum experimental parameters were established and the interference of major elements on the determination of selenium was studied using collection on a cold silica tube. The atom-trapping atomic absorption technique gives a detection limit of 0.03 ppm after 2-min collection on silica in an air—acetylene flame. This compares with ca. 1 ppm by the conventional absorption technique at the same 196.1-nm line. Methods to minimize interferences were examined, including the use of a double tube arrangement, an aluminium oxide-coated silica tube and ion-exchange separation. A combination of combustion in an oxygen flask and collection from an air—acetylene flame on the aluminium oxide-coated silica tube yielded satisfactory results in the analysis of four plant tissue samples.     

Effects of cooling of a nitrous oxide—acetylene burner in atomic absorption spectrometry

A water-cooled burner is used for the determination of silicon, aluminium and calcium geological samples by a.a.s. The cooling modifies and stabilizes the nitrous oxide—acetylene flame so that sensitivity increases and the relative standard deviation decreases significantly in comparison with measurements in which traditional burners are used.     

Detection of OH in an atmospheric pressure flame via laser enhanced ionization of indium

A resonance ionization detector (RID) based on the two-step laser enhanced ionization of indium metal in an atmospheric pressure air/acetylene flame is studied and characterized. Practical utilization of the RID is shown by recording a partial excitation spectrum of the OH radical in the same air/acetylene flame used as the detector cell and measurement of the flame temperature by the Boltzmann plot method. OH transitions were excited in the X²Π → A²Σ⁺(1,0) vibronic band in the wavelength range 281–288 nm. Two possible mechanisms, fluorescence capture and collisional energy transfer, for the observation of the OH excitation spectrum are put forth and discussed. No conclusive evidence supporting either mechanism as predominant was found.     

Measurement of relative atomic transition probabilities using flame atomic absorption spectroscopy

A simple and straightforward technique has been developed to measure relative atomic transition probabilities (A_ji) using flame atomic absorption spectroscopy (FAAS). A_ji values for Cu, Ag, Mn and Mo are calculated from absorption measurements in an air—acetylene flame using both line emission (AAL) and continuum excitation (AAC) sources. For Mn and Mo, large discrepancies for A_ji are found between AAL and AAC, which may be attributed to hyperfine structure (hfs). For continuum source measurements the absorbance is independent of the absorption line profile thus eliminating the problems associated with hfs. Therefore, AAC provides a more accurate method for relative A_ji measurements, with determinations of better than 10% relative standard deviation for all elements.     

The use of lanthanum chloride to prevent interferences in the flame photometric determination of exchangeable calcium in soils

An examination of the interferences of aluminium, bicarbonate, phosphate, sulphate and silicate in the flame photometric determination of calcium in ammonium chloride solutions has shown that, with the exception of bicarbonate, all cause serious interference. Addition of lanthanum to the solution can satisfactorily prevent each of these interferences Provided the lanthanum to aluminium ratio is at least 12.5 I by weight all interference from aluminium can be prevented The use of lanthanum chloride to prevent such interferences in the determination of calcium in ammonium chloride lcachates of soils is discussed and a simple flame photometric method for the determination of exchangeable calcium in soils is proposed.     

Burntgas composition of the heliumoxygenacetylene flame

The burnt gas composition of a potentially important atom reservoir, the HeO₂C₂H₂ flame, is calculated. This flame, compared to the air—acetylene flame, provides a slightly more reducing and a much less quenching environment.     

Stabilization of the plasma-jet flame and determination of aluminium and boron in steel

Summary A stabilization of the plasma-jet flame was studied for the use of acid solutions, the apparatus was improved and working conditions for the determination of aluminium and boron in steel were examined. The coefficient of variation for the determination of aluminium (0.061%) in steel was 4.9%. These determinations are rather difficult by flame spectrometry or atomic absorption spectrometry using the usual combustion flame because of the formation of stable oxides of Al and B.

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Zusammenfassung Die Stabilisierung der Plasma-Jet-Flamme wurde in Hinblick auf die Verwendung saurer Lösungen untersucht. Die Apparatur wurde verbessert und die Arbeitsbedingungen für die Bestimmung von Al und B in Stahl ausgearbeitet. Der Strukturkoeffizient für die Bestimmung von 0,061% Al in Stahl betrug 4,9%. Diese Bestimmungen sind bei Verwendung von Verbrennungsflammen wesentlich schwieriger durchzuführen, da beständige Oxide von Al und B gebildet werden.

     

Surface modified aluminium hydroxide in flame retarded noise damping sheets

Flame retarded polyethylene compounds were prepared using a series of aluminium hydroxide of different particle size applying a milling processes and special precipitation technologies. The processability and flame retardant efficiency of the flame retarded systems were compared. The effects of various surface modifications were analysed in case of one selected type of aluminium hydroxide. A silicone terminated reactive surfactant promoted not only the processability but also the flame retardant efficiency. Noise damping sheets were prepared by simultaneous application of aluminium hydroxide and barium sulphate in an elastomer blend matrix. V0 flame retardant grade could be achieved this way accompanied with improvement in the acoustic properties and maintenance of the mechanical properties.     

Evolved-gas zeeman flame atomic absorption spectrometry for the determination of arsenic compounds

An evolved-gas separation/flame Zeeman atomic absorption spectrometric approach is demonstrated for the speciation and determination of arsenic in oyster tissue. No digestion is needed and separation of inorganic arsenic compounds having similar boiling points is achieved. A stoichiometric or air-rich acetylene/air flame for atomic absorption spectrometry is not generally suitable for arsenic determination because of severe ultraviolet absorption interference at 193.7 nm and low sensitivity; polarized flame Zeeman atomic absorption spectrophotometry with a fuel-rich flame is suitable for the detection of traces of arsenic. The evolved-gas separation/Zeeman atomic absorption approach is simple, based on commercially available instrumentation, and useful for the selective determination of major arsenic compounds. Data are given to demonstrate optimal conditions and to show application to oyster tissue.     

Estimation of sodium in aluminium using the flame photometer

A flame photometric method of estmating sodium in aluminium has been developed. It was found that the concentration of aluminium altered the intensity of the sodium flame. This necessitated using standerd conditions.     

Melamine integrated metal phosphates as non-halogenated flame retardants: Synergism with aluminium phosphinate for flame retardancy in glass fiber reinforced polyamide 66

An integrated multicomponent molecule, Melamine-poly(aluminium phosphate) (Safire^®200), its zinc and magnesium analogues namely Safire^®400 and Safire^®600 respectively were used as flame retardants for glass fiber reinforced polyamide 66 in combination with aluminium phosphinate. Characterisation, thermal stability, combustion properties, glow-wire flammability index and glow-wire ignition temperature and cone calorimetry results are reported. Lower threshold of loading of flame retardants that pass V0 rating in UL-94 vertical burning test have been determined. Effect of Zinc borate (Firebrake^®500 grade) in these formulations was investigated. Influence of additives on endothermic and exothermic transitions of polyamide 66 in these formulations were studied by differential scanning calorimetry. The formulations were evaluated against the properties and fire performances of classical commercial combination of aluminium phosphinate and melamine polyphosphate. All the new formulations down to 15% of additives loading achieve V0 rating according to UL-94 protocol. This synergistic combination of additives significantly reduces the peak of heat release rate (pHRR) and total heat release (THR) in formulations exhibiting various degrees of intumescence.     

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.     

Evaluation of the analytical capabilities of frequency modulated sources in multielement non-dispersive flame atomic fluorescence spectrometry

Frequency modulated sources of Cd and Zn are used to produce modulated atomic fluorescence signals (at two different frequencies) in a non-dispersive flame atomic fluorescence spectrometer. To reduce the flame background level, a chlorine filter, a separated air—acetylene flame, and a solar blind photomultiplier are used. Even so, there is shown experimentally and theoretically to be a multiplex disadvantage, as compared to the conventional single slit scanning dispersive spectrometer, as a result of the flame background photon noise and an additional multiplex disadvantage at high concentrations of an interference, e.g. in the measurement of Zn (213.9 nm), Cd (228.8nm) results in a reduced S/N for Zn when the Cd signal level becomes comparable with the flame background signal level. Little future for multiplexed techniques in atomic flame spectrometry in the u.v.- Visible is predicted.